Planning Search for Multiple Targets using the iPad Y Tsui1, T Horowitz2, I M Thornton1 |
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1Psychology Department, Swansea University, United Kingdom |
| The Multi-Item Localisation (MILO) task is a useful tool for exploring both retrospective and prospective aspects of sequential search (Thornton & Horowitz, 2004 Perception & Psychophysics 66 38-50). A prominent feature of the MILO serial-reaction time function is a highly elevated response to T1 compared to T2 and subsequent targets. This “prospective gap” is thought to reflect forward planning. Here we present two new experiments that use the MILO iPad app to explore this prospective component. In Experiment 1, we randomly varied the sequence length between 2 and 8 items. Responses to both T1 and T2 systematically increased with set size. However, the T2 function had a shallower slope, presumably reflecting the benefit of forward planning. In Experiment 2, all displays contained 8 items, but observers were given a 0-6 second preview before responding. The T1-T2 gap reduced as the preview delay increased, but did not disappear even with a 6 second delay. Thus, forward planning cannot completely account for the gap. Together with our previous findings, these results suggest that the prospective gap is a combination of set-up time for registering a new visual layout, response preparation, and forward planning. |
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