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Khurana B, Watanabe K, Nijhawan R, 2000, "The role of attention in motion extrapolation: Are moving objects 'corrected' or flashed objects attentionally delayed?" Perception 29(6) 675 – 692
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The role of attention in motion extrapolation: Are moving objects 'corrected' or flashed objects attentionally delayed?

Beena Khurana, Katsumi Watanabe, Romi Nijhawan

Received 14 September 1999, in revised form 17 February 2000

Abstract. Objects flashed in alignment with moving objects appear to lag behind [Nijhawan, 1994 Nature (London) 370 256 - 257]. Could this 'flash-lag' effect be due to attentional delays in bringing flashed items to perceptual awareness [Titchener, 1908/1973 Lectures on the Elementary Psychology of Feeling and Attention first published 1908 (New York: Macmillan); reprinted 1973 (New York: Arno Press)]? We overtly manipulated attentional allocation in three experiments to address the following questions: Is the flash-lag effect affected when attention is (a) focused on a single event in the presence of multiple events, (b) distributed over multiple events, and (c) diverted from the flashed object? To address the first two questions, five rings, moving along a circular path, were presented while observers attentively tracked one or multiple rings under four conditions: the ring in which the disk was flashed was (i) known or (ii) unknown (randomly selected from the set of five); location of the flashed disk was (i) known or (ii) unknown (randomly selected from ten locations). The third question was investigated by using two moving objects in a cost - benefit cueing paradigm. An arrow cued, with 70% or 80% validity, the position of the flashed object. Observers performed two tasks: (a) reacted as quickly as possible to flash onset; (b) reported the flash-lag effect. We obtained a significant and unaltered flash-lag effect under all the attentional conditions we employed. Furthermore, though reaction times were significantly shorter for validly cued flashes, the flash-lag effect remained uninfluenced by cue validity, indicating that quicker responses to validly cued locations may be due to the shortening of post-perceptual delays in motor responses rather than the perceptual facilitation. We conclude that the computations that give rise to the flash-lag effect are independent of attentional deployment.

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