Meaningful stimuli inflate the role of proactive interference in visual working memory

The use of meaningful daily objects in visual working memory (VWM) tasks revealed two uncharacteristic findings: enlarged memory capacity, and strong proactive interference (PI), which was previously believed to play only a modest role in VWM. To disassociate the roles of meaning and visual complexity in these effects, a set of stimuli composed of meaningful daily objects was compared to visually similar meaningless sets. These sets were included in a Repeated (PI-prone) condition in which stimuli were repeatedly drawn from a limited set of items, and in a Unique (PI-free) condition in which each stimulus appeared only once. In line with past findings, the results consistently showed superior memory for meaningful stimuli. Importantly, they also showed a stronger PI-effect for meaningful stimuli as the difference between the Repeated and Unique conditions was greatly reduced (Experiment 1) or eliminated (Experiment 2) for meaningless stimuli. Together, these results strongly imply that meaning, and not visual complexity, plays a key role not only in boosting memory capacity but also in inflating the role of PI in VWM.