Similarity and Difference Judgments Under Perceptual and Non-Perceptual Conditions

It has recently been suggested that knowledge is represented in the form of perceptual symbol systems (Barsalou, 1999). According to this view, perceptual states may be used to support higher cognitive processes without being transduced into a representational language. Since the ability to recognize difference and similarity is fundamental for cognition, we examined to what extent it might be based on perceptual information. In three experiments, participants made judgments of similarity and difference for simple items under three presentation conditions: Words Only, Words and Pictures, and Pictures Only. Reaction times for judgments in the Words-Only condition were consistently slower than in the other presentation conditions. However, judgments of perceived similarity and perceived difference did not markedly differ between presentation conditions. The results suggest that participants recruited perceptual information when evaluating similarity in the Word-Only condition. Additionally, presentation condition had an effect on the relation between the similarity and difference scales: for a given degree of similarity, more extreme difference judgments were found under those conditions where words were displayed. We offer an explanation for this effect, and present a further research program.