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Katsumi Watanabe; Reflexive attentional shift caused by indexical pointing gesture. Journal of Vision 2002;2(7):435. doi: 10.1167/2.7.435.
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© ARVO (1962-2015); The Authors (2016-present)
Pointing with the index finger extended is a universal behavior in humans. But, the functional significance of index finger extension in pointing gesture has been rarely examined. We examined the efficacy of pointing gestures in evoking viewer's attentional shifts.  After various hand gestures were presented at the fixation point, eleven observers pressed keys to report the location of a target dot at the peripheral visual field quickly and accurately. When the target was presented 107 ms after the cue, reaction times were shorter to the target at the location where hand gestures pointed (i.e., where the fingers were oriented) (p < .05). This cuing effect was absent when the target appeared 1000 ms after the cue, indicating that the attentional shift is relatively short-lived and is not due to the observer's deliberate strategy. These results showed that directional hand gestures automatically trigger visual attentional shifts toward the pointing direction. Moreover, the indexical pointing gesture produced a significantly larger cuing effect (p < .05) than the other gestures, suggesting that there is a functional significance of indexical pointing in manipulating the viewer's attention.  To examine if the finger position (at the side of the thumb) or the finger length (relatively long) of the index finger accounts for the index-finger's advantage in manipulating attention, we shortened the index finger to the length of the little finger and lengthened the little finger to the length of the index finger. If only length matters, the lengthened little finger would show an enhanced effect as well. If position relative to the thumb is crucial, the shortened index finger would preserve the enhanced effect. Neither was the case. The attentional shift was boosted only with the normal index finger (p < .05). Thus the visual system seems to use rather inflexible visual representation of indexical pointing gesture for modulating reflexive attention.
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