Abstract
Research into the capacity of visual short-term memory (VSTM) using change detection tasks has revealed an estimated limit of around 4 objects which may decrease with increasing information load in the display. We used a cueing technique to examine whether instantiating a response-irrelevant attention set could contribute to greater memory capacity or improved performance. Specifically, we tested whether providing information in advance about the number of objects in the display would enhance performance in a standard VSTM change detection task.
Across several experiments, cueing the number of objects in the display significantly increased change detection performance, even for set sizes within the estimated capacity of VSTM. None of the existing theories of VSTM capacity - either those setting an object-based limit or those setting an information-based limit - predict increased memory capacity due to foreknowledge of the number of objects that will appear in the display. Performance was enhanced by cueing the number of objects at all set sizes. Strikingly, a visual cue enhanced performance more than a numerical or verbal cue, suggesting that visual cues allow more effective tuning of visual attention. Control studies eliminated the possibility that the cueing benefits resulted from general alerting of the participant to the trial start. Our results imply that VSTM capacity - or performance in tasks which measure VSTM capacity - can be improved when participants are able to tune their attention set to the nature of the display, suggesting that VSTM capacity might be more malleable than previously thought. Further studies examine whether cueing a feature dimension similarly affects VSTM task performance.