Categorical judgments do not modify sensory representations in working memory

• Published in: PLoS computational biology Vol. 17; no. 6; p. e1008968
• Main Authors: Luu, Long, Stocker, Alan A.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.06.2021; Public Library of Science (PLoS)
• Subjects: Adult; Approximation; Bias; Biology and Life Sciences; Categorical perception; Estimates; Experiments; Feedback; Female; Human subjects; Humans; Hypotheses; Inference; Judgment; Male; Memory, Short-Term; Mental Recall; Noise; Physical Sciences; Psychological research; Psychophysics; Recall; Representations; Short term memory; Social Sciences; United States
• ISSN: 1553-7358; 1553-734X; 1553-7358
• DOI: 10.1371/journal.pcbi.1008968

Categorical judgments can systematically bias the perceptual interpretation of stimulus features. However, it remained unclear whether categorical judgments directly modify working memory representations or, alternatively, generate these biases via an inference process down-stream from working memory. To address this question we ran two novel psychophysical experiments in which human subjects had to reverse their categorical judgments about a stimulus feature, if incorrect, before providing an estimate of the feature. If categorical judgments indeed directly altered sensory representations in working memory, subjects’ estimates should reflect some aspects of their initial (incorrect) categorical judgment in those trials. We found no traces of the initial categorical judgment. Rather, subjects seemed to be able to flexibly switch their categorical judgment if needed and use the correct corresponding categorical prior to properly perform feature inference. A cross-validated model comparison also revealed that feedback may lead to selective memory recall such that only memory samples that are consistent with the categorical judgment are accepted for the inference process. Our results suggest that categorical judgments do not modify sensory information in working memory but rather act as top-down expectations in the subsequent sensory recall and inference process.