Abstract
Individuals have expectations about how visual features map to concepts in information visualizations. These expectations are called inferred mappings. Interpreting visualizations becomes easier when inferred mappings match the encoded mapping in the legend. Studies on information visualization has found that inferred mappings for colormaps are impacted by the dark-is-more bias, which causes adults to map darker colors to larger quantities (Cuff, 1973; McGranaghan, 1989; Schloss et al., 2019). However, Smith and Sera (1992) suggested this bias is absent in adults for solid squares. We aimed to reconcile these contradicting results by investigating how configuration (square vs. grids in maps) impact inferred mappings. We asked participants to indicate which of two achromatic squares (dark/light) was “more” (methods adapted from Smith and Sera (1992)) and which side of an 8×8 colormap (dark/light) represented more fictitious alien animal sightings (methods adapted from Schloss et al., 2019). We expected participants to show a dark-is-more bias when making inferences about colormaps, but not when making inferences about solid squares. However, participants showed a dark-is-more bias for both tasks (p<.001), and responses did not significantly differ by task (p=.64). Thus, there were no differences between squares and maps to reconcile. To investigate factors that may influence the strength of the dark-is-more bias on inferred mappings in adults, we next tested for effect of background lightness. A new set of participants were presented with the same stimuli on a black background. They were significantly less likely to respond that the darker region mapped to “more” on the black background (p<.001), which is consistent with an “opaque-is-more” bias overriding the dark-is-more bias. This reduction was significantly larger for solid squares than for colormaps (p<.001). The reasons for this interaction are unknown, but the results suggest that multiple configural factors combine to influence inferred mappings between lightness and quantities.