Object-based grouping benefits without integrated feature representations in visual working memory

Visual working memory (VWM) is typically considered to represent complete objects—that is, separate parts of an object are maintained as bound objects. Yet it remains unclear whether and how the features of disparate parts are integrated into a whole-object memory representation. Using a change detection paradigm, the present study investigated whether VWM performance varies as a function of grouping strength for features that either determine the grouped object (orientation) or that are not directly grouping relevant (color). Our results showed a large grouping benefit for grouping-relevant orientation features and, additionally, a much smaller, albeit reliable, benefit for grouping-irrelevant color features when both were potentially task relevant. By contrast, when color was the only task-relevant feature, no grouping benefit from the orientation feature was revealed both under lower or relatively high demands for precision. Together, these results indicate that different features of an object are stored independently in VWM; and an emerging, higher-order grouping structure does not automatically lead to an integrated representation of all available features of an object. Instead, an object benefit depends on the specific task demands, which may generate a linked, task-dependent representation of independent features.