Abstract
A number of researchers have proposed overlapping visual short term memory (VSTM) and spatial attention processes (Awh and Jonides 2001; Mayer 2007). We investigated the extent to which visual spatial attention and visual short term memory rely on dissociable mechanisms (Oh & Kim 2004; Woodman & Luck 2004; Fougnie & Marois 2006) by asking subjects to perform a standard VSTM task (Pashler 1988; Luck & Vogel 1997) in the presence or absence of a rapid serial visual presentation task (RSVP) at fixation. Importantly, the two tasks did not overlap spatially. When the RSVP task was presented during the maintenance phase of the VSTM task, subjects' capacity on the VSTM task was decreased by approximately one item. To further investigate the interaction between VSTM and visual spatial attention, we varied the onset of the RSVP task relative to the onset of the sample display. When the RSVP task was presented prior to the VSTM task, subjects' VSTM performance showed no impairment. When the RSVP task was presented during the maintenance phase, performance decreased. When the RSVP task overlapped or was immediately following the sample presentation, subjects' performance further decreased. Our results suggest that spatial attention is important for the encoding and maintenance of visual short term memory, and that attention is likely used after the sample display to further encode and/or maintain item identities. Although VSTM and visiospatial attention may utilize similar resources, subjects are still able to perform both tasks at once, implying a separation of the systems.
This research was supported by National Science Foundation BCS-0236737 and BCS-0726061 to DCS.