Object Details Persist in Visual Working Memory Regardless of Category Sufficiency for Search

When searching for objects in complex environments, performance often improves with more specific target representations. Yet, sometimes a more general representation may be preferable. For example, when repeatedly searching for unique exemplars from the same object category, a shared category-based representation could help alleviate the cognitive burden of constantly encoding and maintaining new exemplar representations. We therefore examined whether the format of target representations used for search is sensitive to the sustained preservation of object-category membership. Across two experiments, observers searched consecutively for images of real-world objects from the same basic-level category. We recorded contralateral delay activity (CDA), an electrophysiological marker of visual working memory (VWM) maintenance, to assess whether the encoding of object-specific details diminished across category repetitions in favor of more generalized representations. In Experiment 1, we manipulated whether object-category membership alone sufficiently differentiated each unique target from nontargets in the search array. In Experiment 2, we preserved category sufficiency but allowed the targets to additionally repeat at the level of the exemplar to examine how repeatedly searching for the same object differs from repeatedly searching for the same kind of object. We found that while fewer object-specific details were maintained in VWM when category membership was sufficient, the amount of detail only diminished across repetitions of the exact same object. Moreover, observers exhibited sensitivity to the sustained preservation of the target category in the form of perceptual and semantic expectancy violations following category switches, as indexed by N2pc and N400 ERP components. Together, we show that, even though the sustained preservation of a target object category does not continuously reduce the encoding of object-specific details, categorical information is nonetheless represented in parallel. We speculate that object-specific representations principally serve attentional guidance, while categorical representations benefit target-match decisions.