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Miyuki G. Kamachi, Taichi Ishii, Isamu Motoyoshi; Voluntary disattention facilitates global motion detection. Journal of Vision 2013;13(9):1138. doi: 10.1167/13.9.1138.
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© ARVO (1962-2015); The Authors (2016-present)
There is a common belief in neuroscience that voluntary attention always facilitates sensory processing. A number of studies have shown that poor attention reduces neural responses and impairs behavioral performance to visual targets. In contrast to this classical view, we here show psychophysical evidence that voluntary attention to an irrelevant task improves, rather than impairs, detection sensitivity for global visual motion. Stimuli were a conventional random-dot pattern (RDP) in which a proportion of signal dots moved in a coherent direction (leftward / rightward) among noise dots of random directions, and a rapid serial stream of letters (RSVP) in the centre. Human observers were asked to detect coherent motion in the RDP with or without performing the concurrent letter identification task. Coherence thresholds (S/N ratio) were measured for RDPs of various densities, velocities, sizes, contrasts, and durations. We found that in most stimulus conditions, the coherence thresholds were lower when the observers were engaged in the secondary task than when they concentrated on motion detection. This paradoxical improvement in the performance disappeared when the RSVP stream was even more rapid so that the secondary task had a very high load. The subsequent experiments showed that the secondary task elevates, or does not affect, contrast and velocity thresholds for simple motion discrimination, and threshold for detecting spatial modulation of motion direction. The results suggest that voluntary withdrawal of attention can allow us to grasp overall structure of motion by enhancing spatial integration, and/or by suppressing spatial segregation, of low-level motion signals.
Meeting abstract presented at VSS 2013
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