The object as the unit for state switching in visual working memory

Visual working memory (VWM) efficiently maintains active representations and prevents interference by storing some information in a passive state. This study aims to investigate the unit responsible for switching representational states in VWM. The investigation focused on two opposing hypotheses: (a) the unit of switching as a feature (feature-based hypothesis), and (b) the unit of switching as an object (object-based hypothesis). Across three experiments involving 180 participants, participants were instructed to hold two features from either one or two objects in their VWM. In a retention-interval search task, participants searched for a tilted line among distractors and specified its direction. The memory-driven attentional capture effect of the first and second probed colors (indicated by a retro-cue) was examined. Results revealed that only the feature indicated to be probed first could elicit memory-related capture for the condition of separate objects. Importantly, features from an integrated object could guide attention regardless of the probe order. These consistent findings, observed across three experiments with features of different dimensions, same dimensions, or perceptual objects defined by Gestalt principles. They provide convergent evidence supporting the object-based hypothesis by indicating that features within a single object cannot exist in different states.