Visual Short-term Memory Capacity for Simple and Complex Objects

TLDR

Prior studies show mixed evidence: some find lower VSTM capacity for complex stimuli, while others attribute complexity effects to retrieval errors rather than storage limits. The study investigates whether VSTM capacity varies with object complexity. ERPs were recorded during a change‑detection task, measuring sustained posterior contralateral negativity to index VSTM retention. The sustained posterior contralateral negativity was larger for complex than simple objects, indicating that maintaining complex items requires greater neural effort and supporting the view that VSTM capacity depends on complexity.

Abstract

Does the capacity of visual short-term memory (VSTM) depend on the complexity of the objects represented in memory? Although some previous findings indicated lower capacity for more complex stimuli, other results suggest that complexity effects arise during retrieval (due to errors in the comparison process with what is in memory) that is not related to storage limitations of VSTM, per se. We used ERPs to track neuronal activity specifically related to retention in VSTM by measuring the sustained posterior contralateral negativity during a change detection task (which required detecting if an item was changed between a memory and a test array). The sustained posterior contralateral negativity, during the retention interval, was larger for complex objects than for simple objects, suggesting that neurons mediating VSTM needed to work harder to maintain more complex objects. This, in turn, is consistent with the view that VSTM capacity depends on complexity.