June 2007
Volume 7, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   June 2007
Animacy and direction from point-light displays: Is there a life detector?
Author Affiliations
  • Dorita H. F. Chang
    Centre for Neuroscience Studies, Queen's University, Kingston, Canada
  • Nikolaus F. Troje
    Centre for Neuroscience Studies, Queen's University, Kingston, Canada, and Department of Psychology, Queen's University, Kingston, Canada
Journal of Vision June 2007, Vol.7, 481. doi:10.1167/7.9.481
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      Dorita H. F. Chang, Nikolaus F. Troje; Animacy and direction from point-light displays: Is there a life detector?. Journal of Vision 2007;7(9):481. doi: 10.1167/7.9.481.

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      © 2016 Association for Research in Vision and Ophthalmology.

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Abstract

Directional information can be extracted from scrambled point-light displays that are devoid of all structural cues prompting the suggestion of a distinct local mechanism in biological motion perception that may serve as a general “life detector” (Troje & Westhoff, 2006). We investigated this hypothesis by testing the perception of both animacy and direction from point-light stimuli. Coherent and scrambled point-light displays of humans, cats, and pigeons that were upright or inverted were embedded in a random dot mask and presented in saggital view to two groups of naïve observers (n = 12/grp). The first group assessed the animacy of the walker on a six-point Likert scale and the second group discriminated the direction of walking. Across blocks, stimulus duration varied from 200 – 1000 ms. Coherent stimuli appeared more animate than scrambled stimuli (p [[lt]] 0.001) and inversion decreased animacy ratings (p [[lt]] 0.001), although more substantially for coherent than for scrambled walkers (p = 0.007). Similarly, discrimination accuracies were higher for coherent versus scrambled stimuli (p [[lt]] 0.001) and inversion decreased performance (p [[lt]] 0.001), but more substantially for coherent than for scrambled walkers (p = 0.004). Both animacy ratings and discrimination accuracies did not differ for animal type (ps [[gt]] 0.200) nor stimulus duration (ps [[gt]] 0.300). The results indicate that like the ability to discriminate direction, the perception of animacy from scrambled displays is orientation-specific. We suggest that the responsible mechanism uses a dynamic, gravity-dependent framework to assess the presence of life in the environment and is remarkably robust, operating efficiently at limited exposure times.

Chang, D.H.F. Troje, N. F. (2007). Animacy and direction from point-light displays: Is there a life detector? [Abstract]. Journal of Vision, 7(9):481, 481a, http://journalofvision.org/7/9/481/, doi:10.1167/7.9.481.
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