Experimental investigation of effects of representations and contexts on comprehension and generation of line graphs

Experimental investigation of effects of representations and contexts on comprehension and generation line graphs Nana Kanzaki (kanzaki@cog.human.nagoya-u.ac.jp) Graduate School of Information Science, Nagoya University, Japan Kazuhisa Miwa (miwa@is.nagoya-u.ac.jp) Graduate School of Information Science, Nagoya University, Japan shapes of the two graphs were different; therefore, the rep- resentation effect identified and the effects of such perceptual shapes were confounded. One important improvement of an experimental approach in the current study is that we use a set of graphs each of which is completely identical from the other in its perceptual characteristics. Abstract In this study, we investigated the representation effect in com- prehending graphs. Many previous studies have confirmed the representation effect. In Experiment 1, we replicated the rep- resentation effect but using a set of graphs each of which is completely identical from the other in its perceptual character- istics. Participants drew a specific aspect of information from a line graph depending on the relation of x-axis and z-legend of the graph. In Experiment 2, participants were given a con- text for problem solving. The result showed that participants read a graph based on a given context; and the representation effect in comprehension was limited. In Experiment 3, partici- pants generated a line graph by themselves. The result showed that they did not necessarily generate a consistent graph with a given context, and in comprehension the requirement of a context has very strong effects similarly as in Experiment 2. Effects of contexts on graph comprehension Keywords: representation; context; graph comprehension; graph generation Introduction It is efficient to use diagrams for solving problems (Larkin & Simon, 1987). There are many previous studies about effects of graph representation and prior knowledge of the graph readers on graph comprehensions. Effects of representations of graphs on graph comprehension Graphs can be represented as various forms. Different repre- sentations of graphs generated from an identical data set elicit different interpretations of the graphs. We call this effect of representation on graph comprehension the representation ef- fect. The representation effect has been confirmed through var- ious previous studies of graph comprehension. For example, in studies of inferences from bar and line graphs, viewers are more likely to describe x-y trends when viewing line graphs than bar graphs (Zacks & Tversky, 1999; Shah, Mayer, & Hegarty, 1999). By contrast, bar graphs emphasize discrete comparisons (Zacks & Tversky, 1999; Shah et al., 1999). Peebles and Cheng (2003) suggested that the comprehen- sion time of certain information differs depending on the graph structure. Shah and Carpenter (1995) confirmed that x-y trends were comprehended easily, although z-y trends were comprehended with difficulty, using three-variable line graphs (e.g., Carpenter & Shah, 1998). In the preceding studies, a set of two graphs was usually used. Two graphs were generated from an identical data set. The relation of x-axis and z-legend was reversed in one graph from the relation in the other graph. However, perceptual Graphs are used in various situations and often utilized to solve specific problems. When graphs are used in a cer- tain context, their comprehension might be affected not only by their representations but also the given contexts and per- spectives determined by the contexts. We examine the effect of such contexts on the comprehension of information from graphs. Freedman and Shah (2002) proposed a model of graph comprehension using a framework provided by the Construction-Integration (CI) model of text and discourse comprehension (Kintsch, 1988). In this model, the compre- hension of graphs is influenced by the interaction between the bottom-up processes of visual features and the top-down pro- cesses of such prior knowledge as domain knowledge, graph- ical literacy skills, and explanatory skills. Shah and Hoeffner (2002) reported that the comprehension of graphs was diffi- cult if the information in the graphs contradicted the viewers’ prior knowledge. Moreover, Freedman and Smith (1996) ob- served that viewers tended to overestimate the trends of data when their prior knowledge of the domain was activated. However, when viewers read graphs for a specific purpose, they sometimes have perspectives given by a certain context without expectations about the data tendency. In the previous studies of text learning, the effects of the given perspectives were confirmed (Pichert & Anderson, 1977; Schraw, Wade, & Kardash, 1993). If this idea can be expanded to graph comprehension, the representation effect might be affected by such given contexts. The second objective of this study is to investigate how the representation effect and given contexts interact on graph comprehension. It has been noted that constructing, generating, and se- lecting graphs are important for graph comprehension skills (Friel, Curcio, & Bright, 2001). Graphs are often generated by viewers themselves in certain contexts. If the representa- tion effect is affected by given contexts, one crucial question is: can undergraduates generate graphs whose representations are appropriate for the given contexts? The third objective of this study is to investigate whether or not undergraduates generate graphs consistent with the representation effect in