Visual Working Memory Capacity for Emotional Facial Expressions

The capacity of visual working memory is limited to no more than four items. At the same time, it is limited not only by the number of objects, but also by the total amount of information that needs to be memorized, and the relation between the information load per object and the number of objects that can be stored into visual working memory is inverse. The objective of the present experiment was to compute visual working memory capacity for emotional facial expressions, and in order to do so, change detection tasks were applied. Pictures of human emotional facial expressions were presented to 24 participants in 1008 experimental trials, each of which began with a presentation of a fixation mark, which was followed by a short simultaneous presentation of six emotional facial expressions. After that, a blank screen was presented, and after such inter-stimulus interval, one facial expression was presented at one of previously occupied locations. Participants had to answer if the facial expression presented at test is different or identical as the expression presented at that same location before the retention interval. Memory capacity was estimated through accuracy of responding, by the formula constructed by Pashler (1988), adopted from signal detection theory. It was found that visual working memory capacity for emotional facial expressions equals 3.07, which is high compared to capacity for facial identities and other visual stimuli. The obtained results were explained within the framework of evolutionary psychology.