Keeping an eye on serial order: Ocular movements bind space and time

The present study examined whether traveling through serially-ordered verbal memories exploits overt visuospatial attentional resources. In a three-phase behavioral study, five single-digits were presented sequentially at one spatial location in phase 1, while recognition and verbal recall were tested in phases 2 and 3, respectively. Participants' spontaneous eye movements were registered along with the verbal responses. Results showed that the search and the retrieval of serially-ordered information were mediated by spontaneous ocular movements. Specifically, recognizing middle items of the memorized sequence required longer inspection times and, importantly, a greater involvement of overt attentional resources, than recognizing the serially first-presented item and, to a lesser extent, the last-presented item. Moreover, serial order was found to be spatially encoded from left-to-right, as eye position during vocal responses deviated the more to the right, the later the serial position of the retrieved item in the sequence. These findings suggest that overt spatial attention mediates the scanning of serial order representation.