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Kathryn Williamson, Lorna Jakobson, Nikolaus Troje; Life Detection in central and peripheral vision. Journal of Vision 2007;7(9):484. doi: 10.1167/7.9.484.
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© ARVO (1962-2015); The Authors (2016-present)
Gunnar Johansson (1973) was the first to demonstrate that human observers can perceive animate activity solely from information about the movements of dots attached to the joints of an otherwise invisible figure. From even brief exposure to these dynamic “point light” displays, viewers are able to extract surprisingly detailed information, including information about the actor's gender and mental state (e.g., Troje, 2002). Recently, Troje and Westhoff (2005) have suggested that several independent processes are involved in biological motion perception, the most basic of which is a simple form of “life detection” that is automatically triggered by low-level, local motion cues. In support of this, they found that, even when configural information was disrupted through spatial scrambling of the dots comprising a point light walker, participants were still able to judge the direction the walker was facing quite accurately, provided the moving dots were presented in their normal (upright) orientation. Stimuli in this study were presented in central vision and viewing times were unlimited. In the present study, we replicated this basic result using very brief exposure durations (200 and 170 ms). We also went on to show that viewers could achieve above-chance direction discrimination performance with upright, scrambled displays when the targets were presented in peripheral vision. Performance in the periphery, however, varied as a function of the side of presentation and the direction the walker was facing. Specifically, while participants were better at processing right-facing (compared to left-facing) walkers in the right visual field, they were equally accurate at processing right- and left-facing walkers in their left visual field. This interaction was seen both with configural and scrambled displays. This interesting result is discussed with reference to recent studies examining hemispheric differences in spatial attention and body representation, and in the operation of the “mirror neuron” system.
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