August 2012
Volume 12, Issue 9
Vision Sciences Society Annual Meeting Abstract  |   August 2012
A search model for imperfectly detected targets
Author Affiliations
  • Albert Ahumada
    NASA Ames Research Center
Journal of Vision August 2012, Vol.12, 722. doi:
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      Albert Ahumada; A search model for imperfectly detected targets. Journal of Vision 2012;12(9):722.

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

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Under the assumptions that 1) the search region can be divided up into N non-overlapping sub-regions that are searched sequentially, 2) the probability of detection is unity if a sub-region is selected, and 3) no information is available to guide the search, there are two extreme case models. The search can be done perfectly, leading to a uniform distribution over the number of searches required, or the search can be done with no memory, leading to a geometric distribution for the number of searches required with a success probability of 1/N. If the probability of detection P is less than unity, but the search is done otherwise perfectly, the searcher will have to search the N regions repeatedly until detection occurs. The number of searches is thus the sum two random variables. One is N times the number of full searches (a geometric distribution with success probability P) and the other is the uniform distribution over the integers 1 to N. The first three moments of this distribution were computed, giving the mean, standard deviation, and the kurtosis of the distribution as a function of the two parameters. The model was fit to the data presented last year (Ahumada, Billington, & Kaiwi, 2011 VSS) for the number of fixations required to find a single pixel target on a simulated horizon. The model gave a good fit to the three moments for all three observers.

Meeting abstract presented at VSS 2012


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