Chapter 1: Introduction
1.1 Motivation
As computers and the Internet
continue to make their way more and more into everyday life, one of the largest
groups of users is elementary-age children. In 2002, 83% of
Web sites such as Yahooligans! (yahooligans.yahoo.com) and Ask Jeeves Kids (www.ajkids.com/) are examples of portals that children can use to find age-appropriate content for school projects or consumer purchases. Project Gutenberg (www.promo.net/pg/) and the Rosetta Project (www.childrensbooksonline.org/) are examples of digital libraries that provide access to scans of out-of-copyright children’s books from around the world. However, these and many other websites have interfaces with one or more of three crucial problems. First, they do not take into account the information processing and motor skills of children, specifically their difficulties selecting small icons and text links with a mouse. Second, they do not consider children’s searching and browsing skills, specifically their difficulties with spelling, typing, navigating, and composing queries. Third, they do not consider how children prefer to search for things, presenting searching and browsing criteria appropriate for adults but not for children. The ability to select content such as reading material on their own is a powerful motivator for children (Kragler and Nolley, 1996), and many of these websites prevent children from doing so.
Recent work in the Human-Computer Interaction Lab at the University of Maryland has focused on designing digital library interfaces that support and scaffold young children’s abilities to search and browse for information. The QueryKids interface allowed children to find multimedia information about animals in a zooming user interface (Druin et al., 2001). This interface was scaffolded with large, easily clickable icons rather than a keyword search box that required typing; incremental and clearly visible results to show progress as searches were constructed; and a built-in Boolean protocol to prevent children from having to mentally construct Boolean queries manually. Search categories were based on how children liked to look for animals, such as what they ate or where they lived. Revelle et al. (2002) found that 2nd and 3rd grade children were successfully able to use this interface when prompted to conduct both simple (non-Boolean) and Boolean queries 85% of the time.
Based on the success of the QueryKids interface, the International Children’s Digital Library (ICDL, www.icdlbooks.org) software was built using a similar interface with the addition of a hierarchical category browser to allow children to find and read books online (Druin et al., 2003). This interface also consisted of large, easily clickable buttons, automatically constructed Boolean searches, and search categories based on how children like to look for books. Reuter and Druin (2004) found that children in grades 1-5 were able to navigate the category structure to find books in open-ended browsing, but they did not generally use the Boolean capability.
Based on the results of these studies and after observing the use of the ICDL over several years, it is my hypothesis that the structure and presentation of the ICDL category browser discouraged children from creating Boolean searches. While Boolean search is known to be difficult for both children and adults, children are capable of using it both digitally and otherwise (Neimark and Slotnick, 1970; Tversky and Kahneman, 1975). The ICDL category browser was structured using faceted metadata (English et al., 2002), a collection of independent classifiers such as shape, color, and genre, each of which was hierarchical in structure. The categories were presented using sequential or hierarchical menus (hereafter referred to as sequential) (Norman, 1991; Hochheiser et al., 2000). These presentations only allow users to explore one facet at a time. Creating a Boolean query required navigating to the leaves of one facet and selecting one, backtracking to the top of the hierarchy, and then navigating to the leaves of another facet to add another leaf. In addition, some of the top-level categories in the facets were rather abstract (e.g. Format, Genre), and young children may not have understood them (Rosch et al., 1976). I believed these problems might be alleviated by making two key changes to the category browser, one in the structure and one in the presentation.
For structure, I suggested that collapsing the depth of the hierarchical categories might be easier for children to navigate, as has been found for adults (Miller, 1981). Children also may not naturally use hierarchical categorization (Piaget and Inhelder, 1969) and may have trouble understanding abstract, top-level categories in a hierarchy (Rosch et al., 1976). For presentation, I suggested using simultaneous menus (Norman, 1991; Hochheiser et al., 2000), where each facet or branch in a category structure can be explored in parallel. For adults, this design was found to be faster when creating complex queries that required backtracking in the sequential menu design (Hochheiser et al., 2000). However, these two changes yield a design with more categories on the same page, which may be visually overwhelming (Hochheiser et al., 2000). Additionally, it is possible that not all the categories will fit on the screen because of the need to use large, easily clickable category icons, necessitating paging or scrolling to view additional categories.
My research sought to investigate the tradeoffs for children completing searching and browsing tasks between the backtracking and top-level category comprehension required for hierarchical faceted structures presented sequentially and the visual scanning and paging or scrolling required for flattened faceted structures presented simultaneously. Until now, no studies have looked systematically at how children of different ages are able to use hierarchical and faceted structures, simultaneous and sequential menus, and Boolean logic in interfaces designed to support their abilities. This dissertation describes the results of two studies designed to help fill this void.
1.2 Research
Contributions
1.2.1
Children’s Use and Preference of Search and Browse
Interfaces
The major contribution of this research is an analysis of elementary-age children’s use and preference of two different combinations of structure and presentation in category searching and browsing interfaces (see Section 6.1). Previous research with adults has explored different combinations of both structure (e.g. Miller, 1981) and presentation (e.g. Hochheiser et al., 2000) with both simple and complex searching tasks. Previous research with children has compared one combination of structure and presentation (sequential hierarchy) to keyword interfaces (e.g. Borgman et al., 1995), and explored simple and complex searching tasks (e.g. Revelle et al., 2002), and open-ended browsing (e.g. Reuter and Druin, 2004), also with sequential hierarchies. However, previous research has not compared different combinations of structure and presentation for children.
I evaluated two combinations of structure and presentation (sequential hierarchy and simultaneous flat) for two types of searching tasks (simple, one-item searches and Boolean, two-item conjunctive searches) as well as open-ended browsing across three different age groups. I report on statistically significant differences in both searching and browsing behavior, as well as qualitative observations and usability issues. I present specific contributions relating to how children of different ages prefer and are able to conduct and understand searching tasks with these interfaces, and how different task types and searching vs. browsing activities influence performance and preference.
These results may be generalizable to other searching and browsing interfaces for children, such as digital libraries, search engines, and e-commerce applications that allow children to browse using categories. These results are not scaleable to large numbers of categories, which would require either placing many categories on the screen, or large amounts of paging or hierarchical navigation to reach many of the categories. However, young children’s shorter attention spans, slower visual information processing speeds, and smaller memory capacities suggest that large numbers of category choices would not be appropriate for children anyway (Baumgarten, 2003; Kail, 1991; Chi, 1976).
1.2.2
Design Guidelines for Children’s Search and Browse
Interfaces
As a second contribution, I present design guidelines for designers of children’s searching and browsing software (see Section 6.2). I suggest interface design choices for classification and navigation schemes based on previous research as well as statistical results and qualitative observations from my studies. I also suggest choices for category browser structure and presentation based on my study results depending on whether the target tasks are simple searches, Boolean searches or casual browsing.
1.2.3
Working Examples of Interfaces
The final contributions of this research are the ICDL Servlet technology that I developed and the interface design ideas that I created, implemented, and tested for the ICDL and adapted for the studies (see Section 6.3). The Servlet technology represents two and a half years of development activity and nearly 100 Java class files of approximately 16,000 lines of code running in a live application that supports roughly 25,000 visitors a month from 155 countries. This code connects to a mySQL database maintained by another ICDL project team member containing metadata information for over 800 books of approximately 50,000 total pages, as well as information about search categories and user profiles. The interfaces for the studies were derived from the current ICDL searching and browsing architecture that I helped design, build, and test, and the results of the study will feed back into revisions that will be deployed in the live ICDL software. In addition, I expect that designers of other interfaces will be able to use the ideas from my architecture and interface designs to create and improve their own tools.
Chapter 2: ICDL Background
2.1 Project
Description
My research is part of the International
Children’s Digital Library (ICDL), a 5 year research project initiated in 2002
and funded by the National Science Foundation and the Institute for Museum and
Library Services. The ICDL is led by Professor
- to create a collection of more than 10,000 books in at least 100 languages that is freely available to children, teachers, librarians, parents, and scholars throughout the world via the Internet;
- to collaborate with children as design partners in the development of computer interface technologies that support children in searching, browsing, reading, and sharing books in electronic form;
- to better understand the concepts of rights management and "fair use" in a digital age;
- to evaluate the impact that access to digital materials may have on collection development and programming practices in school and public libraries;
- to develop a greater understanding of the relationship between children's access to a digital collection of multicultural materials and children's attitudes toward books, libraries, reading, technology, and other countries and cultures.
The project has two main audiences: children age 3-13 and adults such as teachers and librarians who work with them, as well as international scholars who study children’s literature. The project draws together an interdisciplinary team of researchers from computer science, information studies, education, and art backgrounds. The research team is also intergenerational – team members also include 6 children age 7-11 who work with the adult members of the team twice a week during the school year and for 2 weeks in the summer to help design the software for the ICDL and other research projects in the lab.
The ICDL initially consisted of two interfaces for accessing the current collection of roughly 800 books in 32 languages. The “Enhanced” interface was a Java application that could be run over the Internet using the Java WebStart plug-in and a broadband connection. The “Basic” interface, which I have been the primary front-end developer of, is implemented with Java Servlets on the server side and HTML and JavaScript on the client side and runs well even on a 56K modem. The Enhanced interface, launched in November 2002 when the project first went live, was phased out over the last year due to its advanced technology requirements and difficulty supporting multi-lingual interfaces. The Basic interface, launched in May, 2003, is based on the same design principles but is more accessible.
In the initial implementation of the Basic interface, users could search for books in three different ways. They could spin a globe using a large, easily clickable arrow and then select a continent to see books from, about, or set in that continent (Figure 1). They could use a category browser of 14 hierarchical facets and navigate down 2 to 4 levels to select a single leaf-level category (e.g. the color red) (Figure 2). Finally, they could use keywords to find books with matching metadata in title, author, summary, and publication information. All of these methods searched for books with matching metadata and returned a list of books, presented with thumbnail images of their covers (Figure 3). Users could then select a book and get more information about it on a preview page, such as a summary and authors (Figure 4). Finally, users could choose to read the book using one of three book readers – the Standard reader that presents pages one at a time in HTML (Figure 5), the Comic reader that presents an overview of all the pages using Java WebStart (Figure 6), or the Spiral reader that presents the pages in a spiral using Java WebStart (Figure 7).
Figure 1.
The world search of the ICDL Basic interface
Figure 2.
The old category browser of the ICDL Basic Interface
Figure 3.
Search results page in the ICDL Basic interface
Figure 4.
Book preview page in the ICDL Basic interface
Figure 5.
The Standard book reader in the ICDL Basic interface
Figure 6.
The Comic book reader in the ICDL Basic interface
Figure 7.
The Spiral book reader in the ICDL Basic Interface
2.2 Research
Issues
The ICDL is an extremely fruitful research project. Internationally, our audience is the entire world, which means our users speak different languages and have different customs. This has implications across all aspects of the project. In selecting books to include, our librarians have to deal with different copyright rules for different countries and publishers. Once books are selected, our metadata team has to assist the contributors in providing metadata about the book in its native language and also in English if possible, as well as coordinating a team of volunteer translators to fill in the gaps left by our contributors. Our technology team has to store, process, and deliver book metadata and interface tools in multiple languages, and assist our users to display these languages in their web browsers. Finally, our advisory board keeps tabs on issues of interpretation. They make sure icons, terminology, and book content are understandable and not offensive culturally, religiously, socially, or politically (Hutchinson et al., 2005b).
In addition to being international, our target audience also includes children age 3-13, so we have to design our interface to accommodate their skills and preferences. The interface is icon-based rather than keyword-based, unlike many other digital search environments, and the icons are designed to be large enough so young children can easily click on them. Our interface also provides multiple ways of searching or browsing for books, geared toward different age groups. Previous research indicates that young children prefer the simplicity and concreteness of spinning the globe in the world interface, while older children prefer the category interface, with category choices geared toward their searching preferences (Reuter and Druin, 2004).
While the ICDL is a research project, it is also a service project, and in that regard, we are sensitive to the differing degrees to which our users are digitally enabled. While some of our users are technologically savvy and connect to the Internet with broadband access, many more are computer or Internet novices connecting with 56k modems, often in public locations such as schools or libraries. As such, they may not have the skills or the permission to install browser plug-ins or download large web pages. As a result, much of our design work is focused on making the ICDL broadly accessible by users with different operating systems, browsers, connection speeds, computer skills, and accessibility.
Finally, the ICDL obviously raises many interesting research questions in the library realm. Children search for books in physical libraries differently than adults, and their behavior is similar in digital libraries (Reuter & Druin, 2004). While adults may be interested in bibliographic information such as title or author, children are more likely to focus on physical features of books such as colors and illustrations or genres such as fairy tales or adventures (e.g. Pejtersen, 1986; Cooper, 2002b; Busey and Doerr, 1993; Kragler and Nolley, 1996; Fleener et al., 1997; Reuter and Druin, 2004). The ICDL category browser was designed and continues to be revised to reflect the way children look for books and the terminology they use to do so.
2.3.1
History
The ICDL was originally implemented as a Java application that could be downloaded and run over the Internet using the freely available Java WebStart plug-in and a broadband Internet connection. This Enhanced interface used zooming and animation to allow users to spin a globe or search in a category hierarchy for books. The Enhanced category browser allowed users to create Boolean searches by selecting more than one category. Categories with the same parent (e.g. Red and Blue, both colors) were combined disjunctively (or) while categories with different parents (e.g. Red and Happy) were combined conjunctively (and).
After launching the Enhanced version, the team quickly realized that many of our users were unable to install plug-ins and/or didn’t have broadband access, so the decision was made to create a static, HTML-only version of the software, known as the Basic version. One member of the team started developing a Java program to generate these pages, but left the project before it was complete. I joined the project in February, 2003 and became the primary developer on the Basic software, released in May, 2003. This interface consisted of simple HTML and JavaScript running on a standard Apache HTTP web server. It used the same searching tools and designs of the Enhanced software but presented them in a format accessible to users with slower Internet connections or who couldn’t install plug-ins. The category browser in the Basic interface did not support Boolean search because the team wanted to research how to improve this function before including it.
As the library grew, we knew that generating a static HTML page for every page of every book in the library would not be realistic. As a result, we decided to implement a dynamic version of the Basic software instead. Since our environment was already built using Java, we decided to use Java Servlets. I was the principal architect and programmer for this project, and in July 2003, we republished the Basic software using this technology. Java Servlet technology provides a way to build dynamic web applications using a request-response protocol that extends the standard HTTP request-response protocol. It is available for free on the Java website (www.java.com). Java Servlets are more scaleable and efficient than popular alternatives such as CGI scripting, and unlike both CGI and Microsoft Active Server Pages, Java Servlets are platform independent. Servlet code can either be embedded in an HTML page as script, which is then dynamically assembled into a Servlet class, or else written by extending the Java HttpServlet class to generate HTML. We chose to do the latter because it makes for more modular and reusable code. The downside is that we have to generate our HTML with “print” statements.
2.3.2
ICDL Architecture
The current ICDL Servlet application consists of a package of nearly 100 classes of approximately 16,000 lines of code that I wrote, plus several open source classes that I adapted (e.g. database connection pool). The architecture also includes a separate package of code for the Java book readers that I maintain, and several JavaScript and CSS files that I wrote to control client-side interaction and presentation in a consistent way across multiple browsers and platforms.
Java Servlets require a web server that supports them. There are a number of choices, but the most powerful, freely available one is Apache Tomcat (tomcat.apache.org). Tomcat can be run independently as a complete web server, or be integrated into the standard, more powerful Apache HTTP web server, which is what the ICDL chose to do because the team maintains an HTML-only website on the Apache side with information about the project. Both servers run on a dedicated Linux machine. The Servlets make use of standard JDBC drivers to connect to a MySQL database maintained by another team member to run queries against many of the 41 tables that contain information about books, categories, and users. The application currently supports roughly 25,000 visitors a month from 155 countries.
On startup, Tomcat can be configured to run a context listener class to initialize application-level variables and read application-level data structures into memory or external files. To reduce run-time calls to the database, I created a context listener that accesses the database to create hash tables for a number of commonly accessed structures. These include mappings from search category and book id numbers generated by web page requests to objects containing more information about these objects (e.g. icons and book titles). The context listener also builds a searchable index file of book metadata for each language that we have book metadata for in the library.
Both Apache and Tomcat can be configured to generate log files for web page accesses, but Tomcat also allows you to add special filter classes that intercept every Servlet page request, which you can then use to generate your own log files. I added a filter class to do this so that I could reject page requests from malicious web bots, and create separate log files with additional, application-specific information. In particular, ICDL users are able to register with the site and create personal accounts, where they are asked for demographic information including their age and gender. Using the log filter, I tag entries from users that are logged in with this information so we can analyze usage patterns for different demographic groups.
The remaining classes in the package are either Servlets or classes that support storage or manipulation of data objects in the Servlets. These include object classes for books and categories, comparator classes for sorting books (e.g. by title or author), database connection tools, and a library class of methods I wrote for generating HTML and application constructs (e.g. tables, images, and page headers and footers). The Servlet classes all inherit from a generic Servlet class that contains references to all the constructs built by the context listener on startup. The general design pattern for these classes is to accept an HTTP GET request for the page, read in the url parameters, and reject the request if the parameters are malformed or accept the request and generate HTML based on the information in the parameters.
2.3.3
Software Enhancements
Over the past two years, I have worked on many improvements to the ICDL software, including optimizing database calls with a connection pool, fixing memory leaks, adding the Comic and Spiral book readers as optional interface widgets, and adding an indexed text search. The text search required the integration of Apache Lucene, a freely available Java search engine library that allows you to index and search the content of your web site with advanced feature such as ranked, Boolean, and field-dependent searches. Using Lucene, the Servlet context listener builds indices of the book metadata in multiple languages, allowing users to conduct searches in any one of these languages.
In 2004, I worked with our database developer to redesign our database schema to store book metadata in multiple languages, and then redesigned the ICDL software to allow users to view and search for information about books in multiple languages. For instance, a user can look at metadata information about the book Where’s the Bear (Harris, 1997) in both English (Figure 8) and Japanese (Figure 9). This was a challenging project because of the need to handle data from multiple character sets. Our solution was to use the Unicode character set, which contains a unique encoding for nearly every character in every language. On the server side, we had to make sure our database software and drivers were updated to be Unicode-compliant and our Servlet code specified that data be handled in the Unicode format. On the client side, we had to generate HTML pages with headers indicating that the content being delivered was encoded using Unicode, provide help pages to assist users in installing fonts for character sets not available on their computers, and design interface tools for searching, sorting, and changing the display language.
Figure 8. Where’s the Bear? with metadata information in English
Figure 9. Where’s the Bear? with metadata information in Japanese
In early 2005, I worked with our technology team to convert the ICDL interface into eight additional languages besides English: Arabic, Chinese, French, Filipino/Tagalog, German, Hebrew, Persian/Farsi, and Spanish. This was a multi-step process, which I began by extracting every interface word and phrase shown on the site and placing them in separate property files. We then had volunteers and a paid translation service translate the words and phrases into each of the eight languages. I then updated the Servlet code to use the translated words and phrases from the properties files, depending on the language a user selected to view the site. Finally, I updated the Servlet code to create HTML that would display pages properly in right to left languages (e.g. Arabic, Hebrew, and Persian/Farsi). To accomplish this in a general way without having to have two cases for every page on the site, I relied on a number of built-in features of HTML, most notably the RTL tag, which automatically does things like display the columns of a table right to left instead of left to right. For instance, Figure 10 shows the Book Preview page for Where’s the Bear displayed in Arabic. Not only is the interface translated to Arabic, but also the entire layout of the page is mirrored from the English version to be read from right to left.
Figure 10. Where’s the Bear? shown with an Arabic interface
At the same time we were translating the interface, I also implemented registration and log-in functionality on the site using persistent session information available in Java Servlets. This feature allows users to register with the site to select their preferred interface language and searching interface. This information is stored in our database and loaded into the user’s Servlet session when they log in. Users can access their profile from any computer by logging in, and the demographic information they provide when they register (e.g. age, gender) is recorded in our log files as they access different pages, helping the ICDL team learn more about their users and tailor the interface according to their needs. The interface translation and registration features were both launched in May, 2005.
Most recently, I worked on allowing registered users to save their favorite books to a personal bookshelf. This change was bundled with a complete cosmetic redesign of the ICDL home page and informational portion of the website created by another team member and launched in October, 2005. I incorporated the new color scheme and icon designs into the library portion of site controlled by the Servlet code. For the bookshelf feature, I added database fields in the user table to store a list of books and a list of the last accessed page in each stored book. Users who are logged in can choose to add a book to their bookshelf with a button on the Book Preview page (Figure 11). After adding books to their shelf, users can select the bookshelf icon in the header of the page to access all of the books on their shelf (Figure 12). Users can also select background themes to customize their bookshelf with different monsters, who protect their books. Each time a user views a page in a book on their shelf, the Book Page Servlet automatically records it as the most recently accessed page so that the user can return to where they left off at a later time.
Figure 11. Book Preview page with button to add book to bookshelf
Figure 12. Bookshelf page showing favorite books saved by a user
Chapter 3: ICDL Interface Design Research
3.1 Early
Designs
Based on our belief that the original category browser in the ICDL Enhanced interface was difficult for children to use to create Boolean searches, which was later confirmed by a research study conducted by our team (Reuter and Druin, 2004), we held off including Boolean search in the Basic category browser to research the issue further. This research issue became the focus of my dissertation. I analyzed and identified two major problems related to these concerns, plus two more design issues that I thought could be improved in the category browser design.
Structurally, our youngest users may be more inclined to think perceptually than hierarchically (Piaget and Inhelder, 1969; Nazzi and Gopnik, 2000; Deák et al., 2002). In order to find a leaf-level category in a hierarchy, users had to rely on their hierarchical knowledge. In addition, our youngest users may have had problems understanding the more abstract, top-level categories in the hierarchy. Many researchers have demonstrated that preschoolers and early elementary age children have difficulty categorizing and drawing inferences about high-level subjects (Rosch et al., 1976; Tversky, 1985; Gelman and O’Reilly, 1988). Presentation-wise, users could only explore one facet in the browser at a time, so navigation and backtracking were required to select leaves in different branches.
In addition to these two problems, previous research and our own observations indicated that children often did not differentiate between the leaves and the interior nodes in the facet hierarchies because they were visually identical (Reuter and Druin, 2004). This made it difficult to know whether clicking on a category would descend into the hierarchy or add the category to the current search. Finally, the results of a search in the Enhanced category browser were isolated in a small box at the top of the screen, where users might not know to inspect the results more closely. In the Basic version of the category browser, the results were on a different page altogether.
In the first prototype I developed
to address these problems, rather than navigating each facet sequentially,
users could open different facets simultaneously by clicking on them and having
their leaves radiate from behind them (
Figure 13. Early simultaneous interface idea.
Based on the problems with this interface, the adult team members held a number of meetings and design sessions in the winter of 2004 to come up with other ideas for new searching interfaces. These included a treasure hunt, a book building tool, and a design I created. This last interface, now called “Simple,” consisted of a ring of category icons arranged around a collection of books (Figure 14). These categories were presented as simultaneous menus, and the collection of books shown matched the categories selected. Over the next few months, together with our kids team partners, we critiqued initial sketches of these designs, brainstormed about improvements, and sketched our own versions of new features. While the initial treasure hunt and book building ideas continue to evolve, the Simple interface was an immediate hit, so I chose to pursue this one for immediate implementation. In addition, I also decided to create a more adult version of the Simple interface using text instead of icons and a larger collection of categories. This interface is now called “Advanced” (Figure 15).
Figure 14. The Simple interface
Figure 15. The Advanced interface
3.2 Simple
Interface
The design goal for the Simple interface was to create a tool that elementary-age children could use on their own or with some assistance from an adult. The original ICDL category browser had already addressed issues relating to large icon sizes to support developing motor skills and age-appropriate category choices to support children’s searching preferences. What was missing was more attention to children’s searching and browsing skills. Structurally, I flattened the hierarchies in each of the category facets to a single layer. I then presented a subset of the most popular leaf-level category icons as buttons that functioned as simultaneous menus, arranged around the perimeter of a box showing matching books. The selected categories, which change to a depressed version when clicked, are joined conjunctively, so the Boolean capability is limited to conjunctive ‘and’ searches. Clicking a selected category button unselects it and removes it from the search.
I chose to support only conjunctive Boolean searches for three reasons. First, a number of studies indicate that children have an easier time with conjunction than with disjunction (Neimark et al., 1970; Bloom et al., 1980). Second, the goal of the interface is to narrow down the number of books from a large collection so that children can easily select from a few books. Disjunction will increase or keep constant the number of results while conjunction will decrease or keep constant the number of results. Finally, while the Enhanced ICDL used conjunction between categories and disjunction within category groups, I felt that this would be confusing in an interface where all the categories appear on the same level. When categories are selected, they are combined in an “equation” across the top of the results section to indicate that their combination adds up to the count of the results. This visual tool makes the effect of selecting multiple categories concrete, which is important for children learning to reason logically. Trying to indicate both conjunction and disjunction in this equation would be difficult.
For the design of the category icons, I used round icons rather than the existing rectangular ones because children sometimes got confused about whether they were looking at categories or books since both were rectangles in the old category browser (Reuter and Druin, 2004). Frequent observation of children using software also informed my choice to implement a JavaScript progress bar in the results section as searches are built. I observed that children are impatient if an interface does not respond immediately, and may click a button multiple times if they don’t get immediate feedback, generating undesired or unpredictable results. For users with slow Internet connections or days when the software is receiving a lot of traffic, searches may not be instantaneous. The progress bar lets children know that their action has worked and that the results will appear momentarily.
Placing many icons on the same page meant that they needed to be as small as possible so I could fit a lot on the page, but not so small that they were difficult to click. Hourcade et al. (2003) found that 64 pixel icons are sufficient for children as young as 4 to be able to click, so I chose this size. I followed the advice of Plaisant et al. (1997) to bring the “treasures” of the library to the surface by having books appear on the same page with the search tools. I chose to place the books in the middle of the page, rather than having categories on one side and result on the other, as is common in other interfaces, for two reasons. First, I felt that the books were the most important part of the interface and should be the main focus of the page. Even if a user doesn’t understand how to use the categories, it is clear that the books are the important part of the page. Second, the inspiration for this design, which I originally called “Fisher Price”, came from my observation of toys for young children, which often have a central feature with large buttons around the outside. I felt that using this familiar design might make children more comfortable with the interface. This design turned out to be a nice choice when we translated the interface to languages that are read right to left, because the metaphor remains the same. The downside is that the categories span the far edges of the entire screen, requiring a lot of visual scanning to view all of them.
When no categories are selected, a group of 2 or 3 featured books appears (Figure 14). The results are incrementally updated whenever new categories are added or removed from the search. For instance, if a user selects Rainbow and Fairy Tales, the results show books that match both of these categories (Figure 16). Categories that these results do not appear in are grayed out and unclickable, while categories that these results do appear in remain selectable. This design prevents the creation of no-hit searches.
Figure 16. The Simple interface after Rainbow and Fairy Tales have been selected
Even when the results contain only one book, the remaining categories that this book appears in can still be added to the search. We did this because pilot testing with our kids team indicated that a favorite activity was seeing how many categories could be added to the search. The children frequently would not look at the book(s) selected until they had systematically gone through the interface and added all the possible categories. Keeping these categories selectable also indicates which other categories a book appears in. In addition to selecting categories, users can also refine their search by including keywords and limiting the results to a particular language. The keyword appears as part of the search equation in the results section. The language selection menu is always present in the equation and contains only the languages that appear in the current result set, preventing the creation of no-hit searches. However, it is possible to create no-hit searches when keywords are included in a search.
I analyzed a years’ worth of web log data and research on how young children search for books in both physical and digital libraries (Pejtersen, 1989; Busey and Doerr, 1993; Kragler and Nolley, 1996; Fleener et al., 1997; Cooper, 2002b) to determine what subset of the over 100 existing leaf level categories to present in the interface. Even with this smaller size, I found that I could not fit all the categories I wanted to use on a single screen, so I had to introduce paging or scrolling to accommodate them. I chose paging (over 2 pages) because it is believed to be superior to scrolling in many situations (Mills and Weldon, 1987), and because I wanted the interface to fit on a single screen and download quickly. I designed the interface so all the controls fit on the same page at 1024x768 pixel resolution. An alternative solution might show only a single page of categories, and as selections are made, new category choices could replace old ones that were no longer selectable. However, this design would make the location of categories inconsistent and unpredictable.
This interface addresses all of the concerns I had with the Enhanced category browser interface. Children can rely on perception rather than hierarchical knowledge to find categories because the hierarchy is flattened. Children need only select from concrete, leaf-level categories because the more abstract, top-level categories are removed. Children do not have to navigate and backtrack constantly because the categories are viewed simultaneously. Children do not have to distinguish leaves from interior nodes because there are only leaf nodes. Finally, children can more easily find books because the results are prominently displayed in the center of the page. After usability testing, this design replaced the old ICDL category browser in October, 2004.
3.3 Advanced
Interface
The Advanced interface is based on the design of U.C. Berkeley’s Flamenco interface (English et al., 2002; Yee et al., 2003), as well as many consumer websites such as Sears (www.sears.com) and Epicurious (www.epicurious.com). These sites use various orthogonal category facets (dubbed “faceted metadata” by English et al.) to describe their data. The facets might all appear on one level, or they might be hierarchical, requiring simultaneous or sequential menus within facets to access leaf-level categories. In consumer web sites, this design is an effective way to allow users to specify different features in product, such as cost, manufacturer, and size.
In my implementation, I took the original ICDL category facets and reorganized them into six top level facets: Audience, Appearance, Content, Type, and Subject. Each of these has 3 to 8 of the original ICDL categories underneath it. These all appear on the left side of the search interface, along with a keyword search that can be used separately or in conjunction with a category search. On the right side of the page, I present books that match currently selected categories, or featured books if no categories are selected, as in the Simple interface. Unlike the Flamenco interface, where the home page only shows categories, the results section is always present, keeping the layout of the page consistent and always allowing users to access books.
Selecting any of the links in the 6 sections on the left replaces the links in that section with the subcategories of the selected link. For instance, in Figure 17, I have selected the Color link under Appearance. The other Appearance categories (Format, Length, and Shape) remain accessible as smaller links under the Appearance heading. The Appearance section links are replaced with the various colors available, each indicating how many books match that color. The results side of the page remains unchanged until one of the leaf subcategories (e.g. Red) is actually selected (Figure 18). Selecting Red will change the results section to show all of the Red books in the library. Selectable leaf categories are distinguished from their parent categories by a smaller, italicized font and a count of matching books. I flattened the original category hierarchy in some places so that the subcategories under the top-level facets are always leaves. This provides a consistent, 2-level hierarchy for all facets.
Figure 17. The Advanced interface with Color selected
Figure 18. The Advanced Interface with Red selected
By default, combining multiple categories in a search produces a conjunction. For example, selecting Red under Color and English under Language would return only books that are both Red and English. Keywords can also be added to searches, so one can search for Red, English books about “cats.” A simple form of query preview (Doan et al., 1996) is used as a search is constructed, where categories and subcategories that have no matching books in the current search criteria are grayed out. This feature prevents the accidental creation of no-hit searches and gives users a sense of the size and scope of the library. Using the “Advanced Options” link in the Keyword section, users can narrow their search results to specific aspects of book metadata (e.g. title, author, and publisher). Users can also change the default conjunctive nature of the search to be disjunctive instead by changing the Match menu from “all” to “any”. For example, an “any” search using Red, English, and “cats” would match books that matched any one of these features. After usability testing, this design was added to the ICDL as a new search tool in October, 2004.
Chapter 4: Related Work
4.1 Children, Computers, and the
Internet
4.1.1
Computer
and Internet Use by Children: Growth and Concerns
Children, regardless of their age, income, or ethnicity, are using computers and the Internet more and more every year. In 2002, 83% of homes with children owned a computer and 78% of homes with children accessed the Internet (CPB, 2002). In 2003, 20% of children age 3-4 used the Internet, 42% of children age 5-9 used the Internet, and 67% of children age 10-13 used the Internet (NTIA, 2004).
So, what are kids doing with
computers and the Internet? Not surprisingly, children are most likely to use
the Internet for schoolwork and for games. Top activities include exploration
(e.g. surfing or searching), communication (e.g. email or IM), and
entertainment (e.g. games or downloading music) (CPB, 2002). Children are also
spending their own money and their parents’ online. In 2003,
Amidst all of this activity
however, some flags have been raised about the appropriateness of computers for
children. In a much quoted and rebutted report, the
In fact, this report has some valid
points (Hourcade, 2004). Many studies have linked childhood obesity to the
similar media of television (The Henry J. Kaiser Family Foundation, 2004). Violent
television programming, similar to the violence found in computer games, is
linked to aggression and desensitization (The Henry J. Kaiser Family
Foundation, 2003). However, these fears are grounded in a worst case scenario.
Parents are encouraged to set limits on the amount of time their children spend
with media and which programming they allow (
Haugland (1992) compared preschool children using developmental software to those using non-developmental (i.e. drill and practice) software over a 7 month period. She found that those exposed to developmental software used the computer for a third of the time as those exposed to drill and practices software, but showed significant gains in intelligence, verbal skills, non-verbal skills, problem solving, abstraction, conceptualization, structural knowledge, long-term memory, complex manual dexterity, and self-esteem. The children exposed to the non-developmental software showed gains in concentration, short-term memory, and self-esteem, but showed significant losses in creativity. Children are also not necessarily isolated in their use of computers: 76% of children 6-12 report that there is an adult in the room with them when they go online at home (CPB, 2002). In addition, despite the concerns raised, parents still believe computers are valuable tools for their children: 81% of parents believe the Internet is valuable for their children’s learning (CPB 2002).
Fortunately, researchers have also responded to these criticisms and are looking harder at ways to make computers and technology developmentally appropriate and demonstrate its usefulness. Druin and Inkpen (2001) nicely summarize how designers of children’s technology can do so by asking three questions:
· Why can technology be appropriate for children?
· What activities for children can technology support?
· What changes in technology should be considered for the future?
To answer the first question, they note that technology can provide children with social experiences, control of their world, and ways to be creative. For instance, children can email with other children around the world, construct virtual worlds with certain game software, and tell stories or draw pictures with other kinds of software. All of these activities support the popular educational and curricular theories of constructivist and constructionist learning, discussed in the next section (Piaget and Inhelder, 1969; Papert 1980).
To answer the second question, they note that children frequently cluster around the same computer, even if there are enough for each child to have their own. Other researchers report similar findings, where children prefer to work with a friend, make new friends, and teach each other when working on computers (Druin et al., 1997; Stewart et al., 1999; Clements, 1999). Certain curricular standards encourage group work and social learning (Vygotsky, 1978), so computers that are properly arranged with multiple chairs and integrated into the classroom can support collaborative activity. In addition, computers with multiple mice and Single Display Groupware (Stewart et al., 1999) can support even more collaboration.
Finally, they note that technology of the future should move away from the desktop and into the everyday world. While Clements (1999) notes that children are indeed capable of using desktop computers and that they are able to understand the symbolic objects on the screen as long as they are concrete, embedding technology in the larger world is even more powerful for young children who are so focused on learning through the physical world. Examples have already been developed, including story-telling robots (Druin et al., 1999), stuffed animal playmates (Strommen, 1998), and programmable physical environments called StoryRooms (Alborzi et al., 2000).
4.1.2
Child Development and
Computers
To understand how computers can be used to help children learn and grow, it is necessary to understand a bit about child development. Probably the most influential name in this field is Jean Piaget, a Swiss psychologist whose studies of children in the early 20th century are widely cited and have been used to create developmentally appropriate educational curricula. Although some of his findings and methods have since been challenged, his influence remains strong. Piaget’s main contributions were suggesting that children progress through 4 major developmental stages, and that rather than simply acquiring new skills and information by being taught in these stages, children construct their own models of reality through their experiences with the world around them (Piaget and Inhelder, 1969).
In the first stage, the sensory-motor stage, children from birth to 2 years old use their senses and motor skills to progress from an undifferentiated view of themselves and the world to an understanding of themselves as separate from other objects and as an agent that can act on these objects. By the end of this stage, children achieve object permanence, recognizing that objects continue to exist even if they are out of sight. In the second stage, the preoperational stage, children from 2-7, learn to use play, images, and finally language and text as symbols to represent objects. This stage is characterized by a certain degree of ego-centrism, where children have difficulty taking the viewpoints of others. For instance, if you ask a child to select a picture of how an object will look if you look at it from a certain position, he will pick the picture of how it looks to him presently. Baumgarten (2003) suggests that for children in the preoperational stage, Internet activities that encourage learning and silly fun are good, and that the activities should be brief and simple, as their attention spans are short and their motor skills are not fine-tuned.
In the third stage, the concrete operations stage, children from 7-11 learn to use the symbols they acquire in the previous stage logically. They discover how to reason about conservation of number, mass, and volume, and about how to classify and order things. For instance, a younger child will believe that if you pour a liquid from short, wide glass to a tall, skinny glass, there is more liquid in the taller glass, whereas a child in the concrete operations stage will recognize that the amount of liquid is the same. However, children in this stage can only do this sort of reasoning with concrete objects, and have difficulty with operations that require multiple, systematic steps to complete. In this stage, Baumgarten (2003) notes that children in this age group have improved their motor skills and reading ability, and so enjoy more complex activities that take advantage of these skills, as well as desiring challenge and competition.
In the final stage, the formal operations stage, children 12 and older learn to think logically about abstract things, which often involves testing hypotheses using systematic steps. For children of this age, Baumgarten (2003) notes that in addition to activities that take advantage of these new skills, children of this age are more attuned to the opinions of their peers, and thus enjoy Internet activities that foster social learning and communication, such as chat rooms.
As children progress through these stages, they are not simply acquiring skills by osmosis, but by constructing their own reality, or mental model, of how and why things work (Piaget, 1955). This theory, known as constructivism, is based on two processes that work together but in opposition to help children build their models: accommodation and assimilation. As children experience the world around them and encounter new experiences, they assimilate this knowledge into their existing models. On the other hand, certain experiences contradict their existing models, so they must accommodate these experiences by changing their models to make sense of them.
More recently, a number of researchers have taken issue with some aspects of Piaget’s work (Burman, 1994). Some researchers criticized his informal observation techniques, preferring more rigorous scientific studies. Others considered some of the tasks he had children do to be difficult or confusing, and demonstrated that children were able to accomplish certain tasks at younger ages than he predicted. With respect to children’s abilities to categorize objects, which is of particular interest in designing category browsers, recent research indicates that Piaget’s findings that children progress developmentally from grouping objects according to perceptual features to more abstract concepts like hierarchies may not paint a complete picture of the process. Researchers have found that in addition to developmental skills, both specific domain expertise and cultural norms may influence children’s abilities to categorize. Young children are able to develop expertise in areas of personal interest (e.g. dinosaurs) that lead to more sophisticated categorization skills than developmental theory would predict (Chi et al, 1989; Johnson and Eilers, 1998), and children from different cultures sometimes choose to categorize things differently (Cole et al., 1971; Lucy and Gaskins, 2001). Nonetheless, Piaget’s research and findings continue to influence the fields of child psychology and education.
A second important figure in child development is Lev Vygotsky, a Russian psychologist whose major contribution to the field was the idea that social interaction heavily influences cognitive development (Vygotsky, 1978). He defined the “zone of proximal development”, the time period in which a child could not solve a problem by himself, but could do it if he received help from an adult or peer. Vygotsky argued that psychologists should study children by observing them in this stage, because this is when developmental processes were taking place. In the education world, this theory lead to the idea of scaffolding, whereby adults provide children with more or less assistance depending on their needs, and gradually reduce their assistance as the child becomes more capable (Wood et al., 1976). Wood et al. noted that in a block construction task with 3, 4, and 5 year olds, the youngest children needed to be enticed, assisted, and reassured about their progress, while older children needed only assistance and reassurance, and finally only reassurance.
In the world of computer software for children, the ideas of Piaget and Vygotsky have been appropriated to design developmentally appropriate software and to assist children in learning new skills. In his seminal 1980 book Mindstorms, Seymour Papert takes Piaget’s concept of children building knowledge and extends it by proposing that this knowledge building can be accomplished best by interacting with the environment to actually build things (Papert, 1980). He argues that the “math-phobic” culture that exists in schools is a result of there not being enough materials in our culture for people to work with to help build their mathematical mental models. Math is instead taught in the abstract, with no reference to anything people can relate to. As an alternative, he offered the LOGO programming language, which allows children to construct geometric shapes with a computer. Papert’s theory, known as Constructionism, thus contrasts with Piaget’s Constructivism in that it places more emphasis on learning in a concrete situation, rather than on the eventual movement from concrete operations to more formal, abstract thinking (Ackerman, 2001).
While Papert’s theories have had a profound influence on educational technology, the idea of scaffolding in computer environments has also taken off. In 1994, Soloway et al. proposed that the field of HCI move away from the idea of “user-centered design” and instead focus on “learner-centered design”, using scaffolding in software in the form of coaching, adaptable tools, and different interfaces for different levels. They built a number of applications as exemplars of these techniques, including an editor for learning programming and a physics simulator called Emile for high school students. Guzdial (1995) conducted a study of students’ use of Emile and found that students used and tailored the scaffolding to their needs, learned to program physics models, and learned new ways of looking at concepts like velocity and acceleration. Strommen (1998) used scaffolding to guide the design of interactions with ActiMates Barney, an animated stuffed animal for children 2 to 5. Barney encourages learning by facilitating social play with children alone, with a PC, or with television. Revelle (2003) discusses the use of scaffolding including levels of difficulty and hints in interactive products produced by the Sesame Workshop. She also notes the use of scaffolding in the ICDL in the form of a direct manipulation interface rather than a keyword-based query protocol, incremental and clearly visible results, and a built-in Boolean protocol that prevents children from having to choose between conjunctive and disjunctive queries (Revelle et al., 2002).
4.1.3
Children as Computer Users, Testers, Informants, and
Partners
Given the emphasis in the human-computer interaction world on understanding and working with users, one would expect that designers of technologies for children would work with children. However, it is only recently that this idea has really taken off, because the obstacles to working with children are many. Cognitively, we know children have short attention spans and limited capability to verbalize thoughts and think abstractly. Practically, children go to school during the day and can’t transport themselves to a lab for usability testing or focus groups. Finally, it doesn’t quite fit in with the traditional adult-child power structure (Druin, 1999b).
Druin (1999b) describes the various roles that children can take in informing designs: user, tester, informant, and design partner. The oldest and most common role for children is as a user, with adults observing and recording activity. The strength of this approach is that it is relatively easy to incorporate into the design process, but it is limited by the fact that it usually takes place too late in the process for the findings to change the technology, which gives little input to children and means that it is used more by researchers than industry practitioners. The role of child as a tester was popularized by Seymour Papert at the MIT Media Lab in the development of LOGO (Papert, 1980). In this role, children are observed using the software in the same way as a user, but their feedback is requested earlier in the design process. For instance, Hanna et al. (1998) describe usability testing methods at Microsoft, which include site visits, surveys, card sorting, and paper and live prototype tests. As a result of such testing, children’s ideas may be integrated into the final design, giving them a sense of empowerment. However, the children don’t really have any input into overall design of the technology, which has already been decided by adults.
The idea of children as informants in design emerged in the 1990s. Technologies including a drawing program for kids called KidPad (Druin et al., 1997), a personal communication device for girls (Oosterholt et al., 1996), and an interactive learning environment for teaching ecology (Scaife et al., 1997) were all designed with children as informants. In this process, children are brought in to give input about a technology at different stages of the design process. In addition to testing at the end of the design process, they might brainstorm about new ideas at the beginning of the process by sketching ideas or trying out existing software. The benefit of this role is that children are involved from the beginning, so their ideas are likely to influence the final design to a greater extent, and they will feel more empowered in this role. The downsides are that the adult-child power structure is maintained with adults in charge, and it also takes more time to work with children in this way.
Finally, the role of child as
design partner was developed by Druin to address some of the shortcomings of
the other roles. The idea of partnering with users grew out of research methods
known as cooperative design in Scandinavia (Greenbaum and Kyng, 1991) and
participatory and contextual design in the
Cooperative inquiry adapts the idea of contextual inquiry from adults observing adults in the workplace to kids observing each other use technology. Children take notes or draw pictures with Post It notes rather than writing extensively. Frequently they simply write about likes and dislikes, and then work together with adults to organize them into affinity diagrams to extract the main issues with the software. From participatory design, cooperative inquiry adapts the idea of low-tech prototyping to brainstorm about new technologies by building them first with art supplies like pipe cleaners, toilet paper tubes, and socks before working on actual technology prototypes that may look too “finished” to change or critique. Finally, cooperative inquiry makes use of technology immersion by observing what children do with technologies of the future, before adults even have much idea about what these technologies might be good for.
The advantages of working with children as design partners are that the children are equals in the process from the beginning, giving them a huge sense of empowerment and a big influence on the final design of a technology. The downsides are that children and adults must learn to work together as a team, which can take many months, and researchers must work around the limits of children’s schedules, attention spans, and appetites for junk food. Despite these issues, a number of successful technologies have been created with the help of children as design partners: PETS, and QueryKids (Druin et al., 1997; Druin et al., 1999; Druin et al., 2001), as well as a web authoring tool (Gibson et al., 2003), a digital library for 11-14 year-old children to author stories (Theng et al., 2001), and of course the ICDL.
4.2 Information Visualization for
Searching and Browsing Interfaces
4.2.1
Psychology of Information Visualization
To understand why we design most user interfaces the way we do, with an emphasis on taking advantage of the human perceptual system, it is useful to understand a bit about how this system works. In 1981, Thomas Moran anchored the idea of understanding the psychology of the user firmly into the field of computer science with an introduction to a special issue on the topic in Computing Surveys (Moran, 1981). He noted that users of computers are engaged in goal-oriented activities, but are limited by their short term memory capacity and their tendency to make errors. He divided users into novices and experts, and noted the tradeoffs in defining the success of the system according to various measures such as learning, time, errors, and functionality. He noted that the user’s conceptual (or mental) model of how a system works will influence his success in operating it, and that calculational models of a user’s mental operations were necessary for helping designers of computer systems try to design with the users’ abilities in mind.
Two years later, together with Stuart Card and Allen Newell, he published The Psychology of Human-Computer Interaction (Card et al, 1983), where such a model was presented. The Model Human Processor was presented as three interacting subsystems: the perceptual system, the motor system, and the cognitive system. The perceptual system takes input from the senses, such as the eyes, and transfers it into short-term memory. For the eyes, this process takes on the order of 100 milliseconds (ms). The motor system activates muscles, such as those in the fingers for moving a mouse or typing. These movements occur as a series of small micro movements, each taking about 70 ms. Finally, the cognitive system connects input from the perceptual system to output for the motor system.
The cognitive system consists of two memory areas: short-term memory and long-term memory. Short-term memory holds input from the perceptual system for short periods of time. People can generally hold 7 plus or minus 2 chunks of information in short-term memory at any one time (Miller, 1956). Long term memory holds all of a person’s available knowledge, and while very large, the ability to retrieve information from it depends on whether associations can be made between the information desired as represented in short-term memory and the information as it is stored in long term memory, a process that usually takes about 100 ms.
It has been shown that young children process information more slowly than adults, and that this in turn affects their motor skills, which rely on rapid processing of perceptual input to make adjustments in motor responses. Kail (1991) studied results from over 70 experiments and found that information processing speed increases exponentially with age from young children to young adults. Thomas (1980) noted that this has a direct effect on motor skills, because the slower speed with which children can process information affects how quickly they can adjust their movements. Chi (1976) attributes the deficit in speed to undeveloped processing strategies such as rehearsal and grouping for moving information between short and long term memory and to children’s’ smaller long-term memories.
For motor skills that involve moving a mouse, the total time is governed by Fitts Law, which says that the time T to move the mouse is directly proportional to the distance D to the target and inversely proportional to the size S of the target: T = c * log (2D/S). The constant c includes the times for the perceptual, cognitive, and motor systems to each complete one cycle. For children, this constant will be larger than for adults (Hourcade et al, 2003a). Strommen (1994) also found that children have difficulty holding down a mouse button for long and coordinating dragging and clicking. Inkpen (2001) confirmed this result by showing that children perform better and prefer interfaces with point-and-click interaction to those with drag-and-drop style interaction. Children also struggle with double clicking and multi-button mice (Bederson et al., 1996), and with the idea of multiple buttons, because they aren’t always able to tell left from right (Strommen, 1998; Hourcade et al., 2003a).
In addition to processing speeds
and motor skills, the knowledge that a user has about a system will influence
their performance. This knowledge, or mental model, will influence whether the
user is able to make connections between his perceptions of the environment and
the knowledge he has stored in memory. If people don’t yet have a mental model
of a system, they will rely on previous knowledge of similar systems, which may
or may not match up (Van der Veer and Melguizo, 2002). Two of the earliest
discussions of mental models for computer systems were presented by Young
(1983) and Norman (1983).
4.2.2
Interface Techniques for
Browsing
Based on the knowledge of how the human perceptual, cognitive, and motor systems operate, a number of user interface techniques have been designed to take advantage of their strengths and weaknesses. Ben Shneiderman was a pioneer in this area, recognizing that as long as it was not overloaded, relying on the recognition ability of the visual perceptual system was much faster than waiting for one or more cognitive cycles to recall information or process text (Shneiderman, 1983; Shneiderman, 1998; Card et al., 1999). For visual user interfaces, Shneiderman helped develop a number of techniques to support browsing activities, which he distinguished from searching or information retrieval, because of it’s emphasis on rapid, progressive filtering of results on the fly based on visual scanning of the current result set, rather than more goal-oriented, methodical searching (Ahlberg and Shneiderman, 1994). Chang and Rice (1993) provide a more thorough definition of browsing, which takes into account the context, influences, process, and consequences that affect the user. For the purposes of my research, I am considering browsing an open-ended exploration of an information space and searching a more goal-oriented, task-driven activity.
In 1983, Shneiderman presented the idea of direct manipulation, now a staple of icon-based user interfaces (Shneiderman, 1983). Based on users’ satisfaction with various computer systems, he noted that people were much happier and more productive with systems where they didn’t have to remember programming syntax, but could just remember the semantics of the operations required to accomplish their tasks. These interfaces were characterized by continuous representations of objects of interest and physical actions with mice or joysticks to manipulate them, rather than keyword commands to invoke or act on them. In addition, these actions were rapid, incremental, and reversible, so the user immediately saw the result of his action, understood what happened, and could undo it if he made a mistake. For children who have reached the concrete operations stages and understand symbols, direct manipulation of objects on the screen has all the same advantages as for adults. Schneider (1996) notes that there are additional benefits, particularly for those in the preoperational and concrete operations stages, given children’s smaller long term memories and shorter attention spans, provided the interface is not overwhelmed with too many objects, colors, or motions.
In 1992, Ahlberg et al. took the idea of direct manipulation and applied it to database querying to create dynamic queries (Ahlberg et al., 1992). Rather than requiring users to remember database language syntax or fill in forms to construct queries, they used graphical widgets such as sliders or buttons to allow users to directly control the values they desired for items in the database. In an experiment comparing a query previews interface to two form fill-in interfaces about the periodic table, 18 undergraduate students were faster with and preferred the query preview interface to the other two. Since then, dynamic queries have been used successfully in many interfaces (Shneiderman, 1994; Fishkin and Stone, 1995; Plaisant et al., 1997).
In addition to problems with textual search, two other problems users of database query systems face is getting too many hits, often overwhelming the database, or getting none at all, leading to frustration. In 1996, Doan et al. presented the idea of query previews as a way to avoid these problems. When a user presents a query to the database, rather than returning complete information about the results, the system instead returns summary information about the results, such as the number of hits and certain important features of each result. These previews provide a number of advantages. First, users are less likely to generate no hit queries because these intermediate results indicate what information will be useful to refine their query. Second, it reduces the load on the network and the database by reducing the amount of information returned. Finally, it provides information about the database contents to aid the user in their searching and browsing.
A final problem in database query systems is the separation of query interface and results interface in many systems. Users often must navigate between the two when refining their query, which takes time and requires them to remember what was going on in the interface that is not currently active. In 1994, Ahlberg and Shneiderman introduced the idea of tight coupling, where dynamic query controls and results are presented together on the same screen, and both are rapidly updated to reflect the current state of the query. As users adjust query controls, they are updated to reflect valid choices that remain given the current search. At the same time, results or query previews are updated to indicate how many and what type of results remain. As a result, users avoid no hit queries because they are able to progressively refine their search based on the feedback they get at each step.
The original ICDL Basic and Enhanced category browsers used direct manipulation of icons representing categories to retrieve books. They used a simplified version of dynamic queries that relied on these icons rather than more complex interface widgets like sliders. They used query previews by only enabling category buttons for which there were matching books in the library. Categories for which there were no books were grayed out and unclickable to avoid generating zero-hit queries. In the Enhanced category browser, the results were tightly coupled to the search by presenting on the same screen. The new Simple and Advanced ICDL category browsing interfaces also use all of these methods to make the searching and browsing experience easy.
4.2.3
Structure and Presentation in Category Browsers
Three of the most common structures for classifying information are hierarchies, trees, and facets (Kwasnik, 1999). Hierarchies and trees have long been used to organize items in meaningful ways, from the biological taxonomies to corporate organization charts. Both hierarchies and trees subdivide a set of data using specific rules for distinction between and across levels, but hierarchies also enforce inheritance relationships between parents and children.
Facets, on the other hand, do not require any type of relationship across levels, but are used to classify a set of data in different, equally meaningful ways. For instance, a user searching in a census database might want to search according to age, location, or income, all unrelated but equally useful ways of thinking about data depending on the task at hand. Each individual facet itself might have a single layer of information (e.g. age) or multiple layers arranged in a hierarchy or tree (e.g. country->state->city). The idea of faceted classification in libraries was developed by the Indian scholar Ranganathan in the 1960s (Kwasnik, 1999). English et al. (2002) extended this idea to digital libraries, coining the term “faceted metadata” to describe the orthogonal metadata descriptors by which a collection of items might be cataloged.
In searching and browsing interfaces, hierarchies, trees, and faceted structures are often presented using sequential or simultaneous menus (Norman, 1991; Hochheiser et al. (2000). There are three different possible combinations of these structure and presentation methods (Table 1). In a sequential presentation, users can only navigate down a single branch or facet at a time. If the interface supports backtracking, they must then backtrack to explore other branches or facets. The original Enhanced and Basic ICDL category browsers are examples of this combination. In a simultaneous presentation of a hierarchy, tree, or hierarchical facets, multiple branches or facets can be explored in parallel. Users can navigate within each branch or facet independently without having to backtrack to explore other areas. Microsoft Windows Explorer is an example of a simultaneous presentation of a file hierarchy. Finally, in a simultaneous presentation of flat facets, all the facets are on the same level and can be explored in parallel. The ICDL Simple search category browser is an example of a simultaneous presentation of single flattened layer of facets.
|
|
Simultaneous Presentation |
Sequential Presentation |
|
Flat Structure |
ICDL Simple Search |
Not Applicable |
|
Hierarchical Structure |
Microsoft Windows Explorer |
Old ICDL Category Browser |
Table 1. Combinations of structure and presentation
The sequential presentation has the advantage of allowing users to contend with only a small amount of information at a time, at the expense of backtracking to explore other areas. By contrast, the simultaneous presentations have the advantage of avoiding backtracking between branches or facets, at the expense of a more complex visual presentation consisting of many branches and facets.
In hierarchical structures, tradeoffs must be made between the depth of the individual branches or facets – how many levels – and the breadth – how many items per level when the structure has more than one level. Miller (1981) noted that large breadth will increase search time because the number of items is large, while large depth will also increase search time not only because of the increased number of selections that will need to be made, but also because of limitations of short term memory in keeping track of location in the structure. Many studies have been conducted with adults to try to understand the optimal depth/breadth ratio, and all are in agreement that broad, shallow presentations seem to be better than deep, narrow ones.
Miller (1981) was the first to establish this claim, comparing 4 hierarchies of 64 English words that varied in depth from 1 to 6 levels and in breadth from 2 to 64 items. He obtained U-shaped results curves for both speed and errors, with the best performance on a hierarchy of 2 levels with 8 choices per level. Snowberry et al. (1983) replicated Miller’s experiment with similar results, but also found that if the condition with all 64 items on one screen was organized categorically rather than randomly, it had the best performance times. Kiger (1984) also conducted a variation of Miller’s experiment that confirmed his results, and also measured user preference, which was consistent with performance data.
Lee and MacGregor (1985) used minimization formulae on the human and computer factors of searching, including visual scanning, key pressing, and computer response time to conclude that the optimal number of items per level was 4-8, which is also consistent with Miller (1956) and his theory of 7 plus or minus 2 items in short-term memory at once. Jacko and Salvendy (1996) conducted similar experiments but also asked users to judge the relative complexity of hierarchies of different depths. They found that users perceived that complexity increased as depth increased. More recently, Zaphiris and Mtei (1997) and Larson and Czerwinski (1998) performed similar experiments on the web, and also found that performance decreased as depth increased.
These previous experiments all dealt with sequential menu presentations, but I believed the results would also be true for individual hierarchical branches or facets in a simultaneous menu presentation. The remaining question in my mind was under what circumstances, if any, are sequential menus superior to simultaneous menus, and vice versa. Hochheiser et al. (2000) compared sequential and simultaneous menus in a web application for browsing census data using hierarchical facets with adults. They found that for simple tasks that did not require backtracking, adults were significantly faster with sequential menus, but for more complex tasks requiring backtracking and selection from multiple facets, they were significantly faster with simultaneous menus. There was no significant difference in preference between the two menu presentations.
While sequential menu designs are ubiquitous, it is only recently that simultaneous menus have been used more extensively in computer interfaces. Ahlberg (1992) was among the first to use the idea of simultaneous menus, using them as dynamic queries in a faceted database about movies. Plaisant et al. (1997) used them in the National Digital Library web interface. Shneiderman et al. (2000) used hierarchical simultaneous menus arranged on two axes, called hieraxes, to visualize data points in a digital library. Marchionini and Geisler (2000) employed simultaneous menus in the Open Video Digital Library to allow users to search for video clips by various facets. Yee et al. (2003) developed the Flamenco browser, using simultaneous menus to allow users to browse the facets of a fine arts database and found that users were more successful and preferred this interface to keyword searching. Naaman et al. (2004) used the Flamenco toolkit to present the results of automatically generated metadata for digital photographs. Reti et al. (2004) used a similar technique to present multimedia metadata in a P2P search system. Gibson (2004) used simultaneous menus to create an overview browsing system for the world wide web.
Today, consumer web sites such as www.sears.com, www.bizrate.com, and www.epicurious.com have found that simultaneous menus are an effective way to allow adult users to specify different features they would like in product. Information technology companies such as Endeca (www.endeca.com), Inxight (www.inxight.com), and i411 (www.i411.com) all offer customized software for business to create simultaneous menu-based search interfaces for their web sites.
4.2.4
Hierarchies vs. Other Forms
of Organization for Children
While there is no previous research to indicate if or when sequential or simultaneous menus are a superior presentation tool for children, some research indicates that flatter structures based on simple features may have some advantages over hierarchical structures in searching and browsing interfaces for children. A number of studies in cognitive psychology indicate that hierarchical organization is not the initial way young children group objects. Piaget was among the first to note young children’s reliance on concrete, perceptual features when understanding the world around them. He suggested that it is only in later stages of development that they begin to think more abstractly and learn about things such as relational or functional hierarchies (Piaget and Inhelder, 1969).
A number of other studies support these findings. Tversky (1985) studied 3, 4, 6, and 9 year olds and found that when grouping objects, perceptual groupings by facets such as shape and color decreased with age and taxonomic groupings by shared category increased with age. Gentner and Namy (1999) found that 4 year olds were equally likely to select a perceptual match or a categorical match for a particular object. Nazzi and Gopnik (2000) found that when categorizing objects, 3 ˝ year olds preferred to group by similar perceptual facets like shape and color than by similar causal features like function. Deák et al (2002) found that both 3 and 4 year olds preferred to sort objects by shape when given no instruction.
However, researchers have also found that young children do accept other ways of categorization besides perception, including simple hierarchies based on more abstract concepts like cause and function. Gentner and Namy (1999) found that when presented with multiple instances of a given category object instead of just one, 4 year olds were more likely to select a categorical match than a perceptual match. Nazzi and Gopnik (2000) found that by age 4 ˝, children preferred grouping by causal features to perceptual features. Deák et al (2002) found that 4 year olds could group objects by function if instructed to do so. Nguyen and Murphy (2003) found that children as young as 4 could group objects related by taxonomy, theme (e.g. dog and leash), script (breakfast foods), and evaluation (e.g. junk foods). Hayes and Younger (2004) found that both 6 and 10 year old children were more likely to recall category information that was both functional and perceptual about imaginary aliens than information that was merely perceptual, and were also better able to categorize aliens according to the functional and perceptual information.
While Piaget asserted that
children’s categorization skills develop through well-defined stages and that
these skills apply globally to all domains, more recent research indicates that
localized domain expertise and cultural norms can also influence children’s
categorization skills. Chi et al. (1989) found in two studies that 6 and 7
year-olds with dinosaur knowledge categorized dinosaurs using hierarchical, domain-related
information that were not necessarily visual (e.g. where it lives, how it
defends itself), whereas children with little dinosaur knowledge sorted more
often based on non-hierarchical, visual attributes. Johnson and Eilers (1998)
found that adults and 5-9 year olds with similar dinosaur expertise were able
to categorize unfamiliar dinosaurs equally well. However, adults performed
better when categorizing an unfamiliar domain (birds), indicating that
developmental differences still play an important role in categorization
skills. Cole et al (1971) found that Kpelle children from
While it is thus possible for young children to categorize using abstract principles, when young children are asked to group hierarchically, some difficulties can arise. Rosch et al. (1976) were among the first to demonstrate young children’s difficulties with higher levels of categories. Preschool, kindergarten, and 1st graders could all sort basic level categories (e.g. cats and cars) more than 90% correctly but could only sort super ordinate level categories (e.g. animals and vehicles) correctly less than 60% of the time. Gelman and O’Reilly (1988) found that both pre-schoolers and 2nd graders could draw inferences about objects in basic level categories, but that the older children drew more inferences about super ordinate level categories.
4.2.5
Boolean Search
It has long been known that people have difficulty with Boolean logic, the use of the connectives AND, OR, and NOT to determine whether statements are true or false (e.g. Tversky and Kahneman, 1975). With the advent of computer databases, this problem showed up in query languages for databases for finding matching records (Zloof, 1975), and later in digital library catalogs (Hildreth, 1983), where people frequently misused this feature or didn’t bother to use it at all to retrieve bibliographic records (Borgman, 1986). The crux of the issue is that in conversational language, AND is an inclusive term, while in logic, it is exclusive, and vice versa for OR (Johansson and Sjolin, 1975).
Children also have difficulty with Boolean logic, particularly disjunction, though they are still capable of using it. Children as young as 2 years old use and understand conjunction in conversational language (Bloom et al., 1980), and by age 4 use and understand disjunction in conversational language (Johansson and Sjolin, 1975). However, Neimark et al. (1970) found that children didn’t understand the use of Boolean conjunction until the 4th grade and Boolean disjunction until high school. For children age 5-13, Snow and Rabinovitch (1969) found that children’s ability to complete Boolean tasks, both conjunctive (AND) and disjunctive (OR), using card matching increases with age, but that across all age groups, they made more errors on disjunctive tasks. Rawson et al. (1973) demonstrated that performance improves with age with disjunctive card matching tasks for preschool children, and that even the youngest children performed better than chance. However, even by high school, children struggle with using keyword-based interfaces to create Boolean searches in digital libraries. Nahl and Harada (1996) found that nearly half of 191 students confused AND and OR when creating Boolean keyword searches in a digital library.