May 2008
Volume 8, Issue 6
Free
Vision Sciences Society Annual Meeting Abstract  |   May 2008
Probability summation and phase spectrum are sufficient to support animal detection in multiple scenes
Author Affiliations
  • Carl Gaspar
    Centre for Cognitive Neuroimaging (CCNi) and Department of Psychology, University of Glasgow, Glasgow, UK
  • Guillaume Rousselet
    Centre for Cognitive Neuroimaging (CCNi) and Department of Psychology, University of Glasgow, Glasgow, UK
Journal of Vision May 2008, Vol.8, 331. doi:10.1167/8.6.331
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      Carl Gaspar, Guillaume Rousselet; Probability summation and phase spectrum are sufficient to support animal detection in multiple scenes. Journal of Vision 2008;8(6):331. doi: 10.1167/8.6.331.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Observers can detect animals in natural scenes rapidly and accurately. Rousselet et al. (Nat. Neurosci. 2002) briefly flashed (26 ms) 2 natural scenes, both in the periphery (centered at 3.6 deg). In these conditions, animal detection was slightly less accurate compared to when observers viewed a single scene. However, probability summation successfully predicted the decrement in d-prime for the double-scene condition compared to the single-scene condition. We retested the double- and single-scene conditions, and employed a novel condition where observers viewed 2 animal scenes. Three observers performed a rapid go/no-go animal/non-animal categorization task in all 3 experimental conditions: single-scene, target-plus-distractor, and double-target, with a total of 8,960 trials per observer. Probability summation was successful in accounting for the pattern of d-prime across the experimental conditions.

Consistent with previous modeling work, we found that an amplitude-only classifier could perform our task. If observers used amplitude spectra to perform our task, then resetting amplitude spectra to be the same across all images should lower d-prime. This is what we found. However, altering amplitude spectra introduces distortions that could even affect a phase-only observer. To test this hypothesis, amplitude spectra were swapped across images, but only within an image category. In these conditions, an amplitude-only observer should perform just as well as with the original images. Contrary to the amplitude-only hypothesis observers had lower d-primes for these amplitude-swapped images compared to normal images. Furthermore, this experiment led to the same low d-primes that were obtained in the amplitude-equalized experiment. This is consistent with the idea that the amplitude manipulations in both these experiments introduce distortions affecting our ability to extract phase information.

Gaspar, C. Rousselet, G. (2008). Probability summation and phase spectrum are sufficient to support animal detection in multiple scenes [Abstract]. Journal of Vision, 8(6):331, 331a, http://journalofvision.org/8/6/331/, doi:10.1167/8.6.331. [CrossRef]
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