No evidence for a fixed object limit in working memory: Spatial ensemble representations inflate estimates of working memory capacity for complex objects

Abstract

A central question for models of visual working memory is whether the number of objects people can remember depends on object complexity. Some influential "slot" models of working memory capacity suggest that people always represent 3-4 objects and that only the fidelity with which these objects are represented is affected by object complexity. The primary evidence supporting this claim is the finding that people can detect large changes to complex objects (consistent with remembering at least 4 individual objects), but that small changes cannot be detected (consistent with low-resolution representations). Here we show that change detection with large changes greatly overestimates individual item capacity when people can use global representations of the display to detect such changes. When the ability to use such global ensemble or texture representations is reduced, people remember individual information about only 1-2 complex objects. This finding challenges models that propose people always remember a fixed number of objects, regardless of complexity, and supports a more flexible model with an important role for spatial ensemble representations.