Abstract
Hung, Wilder, Curry & Julesz (1995) used sequential and simultaneous presentations to distinguish the encoding and storage limitations of visual short term memory. They found that simultaneous presentation led to better recall than sequential presentations and that with sequential presentations a slower rate of presentation (SOA of 50 ms) led to better recall than faster rates of presentations (SOAs of 33 ms and 17 ms). They argued that information is encoded differently from sequential and simultaneous visual presentation and that with sequential presentation sufficient time is required to encode each incoming item. Here we apply the Hung et al methodology to test whether the process of selection, as opposed to the process of encoding, follows the same pattern. We used Multiple Object Tracking (MOT) as a measure of whether visually cued items had been selected under various conditions of temporal presentation. In contrast to the Hung et al findings with item recall, we found that item selection was better when the items were sequentially cued (as shown by better MOT performance) than when they were simultaneously cued, while there was little difference at the different presentation rates in the SOA range used in the Hung et al study. This finding further supports our earlier claim that selection and tracking may not involve memory because items' properties are not encoded into VSTM in the course of selecting and tracking objects in MOT (Scholl, Pylyshyn & Franconeri, ARVO1999).
Supported by NIMH Grant 1R01-MH60924 to ZWP