Structure and strategy in encoding simplified graphs

Abstract

Tversky and found a systematic bias toward the 45 0 line in memory for the slopes of identical lines when embedded in graphs, but not in maps, suggesting the use of a cognitive reference frame specifically for encoding meaningful graphs. The present experiments explore this issue further using the linear configurations alone as stimuli. Experiments 1 and 2 demonstrate that perception and immediate memory for the slope of a test line within orthogonal "axes" are predictable from purely structural considerations. In Experiments 3 and 4, subjects were instructed to use a diagonal-reference strategy in viewing the stimuli, which were descrfbed as "graphs" only in Experiment 3. Results for both studies showed the diagonal bias previously found only for graphs. This pattern provides converging evidence for the diagonal as a cognitive reference frame in encoding linear graphs, and demonstrates that even in highly simplified displays, strategic factors can produce encoding biases not predictable solely from stimulus structure alone.

Prototypes and particulars: Geometric and experience-dependent spatial categories.

“…Geometric cues may be more certain because they are specified by the perceptual structure of the task space (e.g., visible lines and symmetry axes) rather than by information derived from memory. It is possible, however, that adults are able to flexibly weight these two category cues (for related ideas, see Curiel & Radvansky, 1998;Newcombe & Huttenlocher, 2000;Schiano & Tversky, 1992). We suspect, for example, that adults would show larger induced category effects in tasks in which there were clear advantages to using experience-dependent cues.…”

“…We thought this would be unlikely, however, because diagonal axes are perceived less accurately than vertical and horizontal symmetry axes (e.g., Beh, Wenderoth, & Purcell, 1971;Cecala & Garner, 1986;Wenderoth, 1997;Wenderoth, Johnstone, & van der Zwan, 1989). Moreover, adults sometimes fail to use diagonal axes to categorize space, even when such axes are readily available (Schiano & Tversky, 1992;Tversky & Schiano, 1989). Another possible category boundary was the horizontal midline symmetry axis.…”

“…It is important to note that, although we did not find cross-category effects, this may not always be the case. For instance, cross-category effects may arise when adjacent spatial categories are separated by a less certain boundary such as a diagonal symmetry axis (for a discussion of related issues, see Engebretson & Huttenlocher, 1996;Schiano & Tversky, 1992;Tversky & Schiano, 1989).…”

“…Figure 1A shows a schematic of results from a study in which adults were shown a target angle within a "V" frame and asked to reproduce this angle after a short delay (Engebretson & Huttenlocher, 1996). Adults' directional responses were biased in the directions indicated by the arrows in the figure: away from midline and away from the edges of the perceptual frame (for related results, see Sandberg et al, 1996;Schiano & Tversky, 1992;Tversky & Schiano, 1989). A second example of this response bias is shown in Figure 1B.…”

“…That is, people might flexibly use category boundaries to optimize performance given particular task demands. For example, Tversky and Schiano (Schiano & Tversky, 1992;Tversky & Schiano, 1989) reported that adults used different category boundaries when figures were presented as "graphs" than when they were presented as "maps." It is important to note, however, that even when adults flexibly use category boundaries, these boundaries are still linked to the perceptual structure of the task space (i.e., reference lines and symmetry axes).…”