Abstract
Subjects viewed two visual displays that were separated by a short blank delay. The task was to decide whether the displays were the same or different. The displays sometimes consisted of coloured disks, sometimes of conjunctions of colour and orientation, and sometimes of moving dots. This visual short-term memory (VSTM) task was paired with a concurrent speeded pitch discrimination task. We summarize a series of experiments that revealed mutual interference between the VSTM task and the concurrent speeded choice task. This interference suggests that VSTM encoding requires central processing capacity that is also required for the speeded choice task. The experiments explored the nature of the capacity limitation, the generality of the effect, and the locus of interference.