Creative Education 2012. Vol.3, No.1, 126-133 Published Online February 2012 in SciRes (http://www.SciRP.org/journal/ce) DOI:10.4236/ce.2012.31021 Trees and Nests: A Comparison between Two Hierarchical Metaphors in Educational Applications Adi Katz Department of Industrial Engineering and Management, Shamoon College of Engineering, Ashdod, Israel Email: adis@sce.ac.il Received December 2 nd , 2011; revised January 6 th , 2012; accepted January 17 th , 2012 The aim is to determine whether one of two hierarchical metaphors, the tree (parent-child) or the nested (object-container), is more suitable for designing educational interfaces for children. To cope with this is- sue an experimental educational application was designed with a prototype for each hierarchical metaphor. The application was evaluated in a laboratory experiment, where children participants interacted with the prototypes to find answers for questions that require searching for information. Task performance was measured in terms of effectiveness, efficiency and subjective aspects such as user perception of ease of use and user preference. The nested (object-container) metaphor was found to be preferred by users and superior in several objective parameters of performance efficiency, but no significant differences were found in the perceived ease of use and in the performance effectiveness. Implications for designing edu- cational applications are discussed. Keywords: Human Computer Interactions; Metaphoric Interfaces; Hierarchical Information Organization; Educational Applications; Usability; Children Interfaces Design Introduction Today, more than ever, children are exposed to computers in their early years of development and have easy access to com- puters and the Internet. Children use the Internet for school- work, playing games and communicating with each other, and are typically involved in activities that require searching and browsing for information (Hutchinson et al., 2006). Creating interfaces for young children presents particular challenges, and the designers of such applications must take into consideration that children are different than adults in the way they think and learn. An important requirement for an effective learning proc- ess is to foster a positive attitude and affect that nourish moti- vation, arouse curiosity, engage creativity, and turn the brain into an effective learning organism (Norman, 2004). It is most important that applications for children are provided with suit- able interfaces that make both their learning process and their interaction with the application easy and enjoyable. A successful user interface paradigm is to design the hu- man-computer interaction based on metaphors already familiar from real life objects, actions and situations. A metaphoric system simply replicates the real life objects and portrays them in the computerized environment, so that the user can intui- tively manipulate objects and work in a familiar manner. A suitable metaphor enables the user to function effectively in the new system, and helps overcome cognitive limitations in com- plex tasks (Te’eni et al., 2007). One of the implications of the cognitive load theory (CLT) in the area of instructional design is that the layout should be intuitive, so that the mind’s capacity for processing information will not be overloaded and user activities will be focused on the concepts to be learned (Sorden, 2005). Instead of learning the system and its features, meta- phorical designs free some of the users’ limited cognitive re- courses so they can be fully engaged and devoted to the data and the activities at hand. When cognitive resources are unnec- essarily devoted to mental activities such as retrieving from memory and learning new objects and actions, it may be at the expense of performance. Metaphors have a particularly impor- tant function in interfaces for young children (Ellis & Blashki, 2001; Gilutz & Black, 2010), are highly preferred by them and can induce curiosity and pleasure (De Angeli et al., 2006). A useful metaphor must be suitable for the user population (Katz & Vaserman, 2009), and therefore, when designing for young users, the chosen metaphor must be borrowed from their eve- ryday environment or conceptual world. In order to cope with the overwhelming diversity of objects and properties in the world, people mentally group objects, treating them as instances of categories instead of as unique individuals. Hierarchical organization is one type of a natural evolution of a classification system in which people notice both distinctions and similarities among objects, and organize cate- gories into hierarchies in which more specific classes are in- cluded in more general ones (Markman, 1989). In other words, many natural categories are hierarchically organized into nested class-inclusion relations, where some classes are super-ordinate or subordinate to others. For example: organisms/plants/flow- ers/Composite family/daisies/erbera daisies. Collins and Quil- lian’s (1969) Hierarchical Network Model of semantic memory states that concepts are stored and represented as nodes within a hierarchical structure in our long-term memory (LTM), with meaningful associations between concepts. The “Is A” link is the most common link in this semantic network model. Browsing for information is a methodical activity with a spe- cific goal, which requires progressive filtering of results based on visual scanning and searching. Since hierarchical organiza- tion stems from greater accumulation of knowledge and ex- perience (Markman, 1989), children have a difficulty dealing with hierarchies when searching and browsing. Children do not always navigate efficiently between categories, they may not Copyright © 2012 SciRes. 126