Probing the Methodology and Interpretation of Learned Categorical Perception Research
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Learned categorical perception (CP) is a phenomenon where learning to place objects in categories influences how similar they appear, with objects in different categories becoming easier to tell apart and/or objects in the same category becoming harder to tell apart. Despite these effects being widely demonstrated, past studies exhibit low statistical power and the literature lacks a unifying theoretical framework. We seek to rectify these issues by conducting a systematic methodological investigation of learned CP, starting with replicating the effect under the conditions with which it has traditionally been reported, then exploring how successive methodological changes impact the presence of the effect. Our replication failed to show a pattern indicative of learned CP from comparing discrimination performance between a group that had learned a category distinction and a control group that had not. Through exploring our data to scrutinize possible key differences between our study and previous demonstrations of learned CP, we hypothesized that a combination of our stimuli being too easy to discriminate and the memorization of individual stimuli along each dimension obstructed the influence of category membership on discrimination behavior and was responsible for the absence of CP effects. We addressed this issue by lowering the discriminability of stimulus pairs and by increasing the number of stimuli in each category. Preliminary results suggest a possible learned CP effect and we plan to collect additional data to clarify the nature of the pattern.