June 2007
Volume 7, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   June 2007
Do rare features pop out? Exploring the boundaries of the low prevalence effect
Author Affiliations
  • Anina Rich
    Visual Attention Laboratory, Brigham & Women's Hospital, and Harvard Medical School, Harvard University
  • Melina Kunar
    Department of Psychology, Warwick University
  • Michael Van Wert
    Visual Attention Laboratory, Brigham & Women's Hospital
  • Barbara Hidalgo-Sotelo
    Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology
  • Jeremy Wolfe
    Visual Attention Laboratory, Brigham & Women's Hospital
Journal of Vision June 2007, Vol.7, 708. doi:10.1167/7.9.708
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      Anina Rich, Melina Kunar, Michael Van Wert, Barbara Hidalgo-Sotelo, Jeremy Wolfe; Do rare features pop out? Exploring the boundaries of the low prevalence effect. Journal of Vision 2007;7(9):708. doi: 10.1167/7.9.708.

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

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Abstract

A search for a rare target in a complex display is important in a number of important tasks, including baggage screening at airport security, or screening for cancerous cells. Wolfe, Horowitz and Kenner (Nature, 435, 2005) demonstrated that the probability of missing a target increases as target prevalence decreases. These high error rates seem to occur because low prevalence encourages participants to set a response criterion that causes them to make rapid ‘target-absent’ responses. Wolfe et al. used complex approximations of luggage x-rays as stimuli. Last year, we demonstrated that the effect of low prevalence could be seen with less complex stimuli where the search is nonetheless relatively inefficient (a search for a T among Ls; Rich et al. VSS 2006). How far can this effect be pushed? In simple feature search tasks, the target is said to “pop-out”. Would observers miss a horizontal target among vertical distractors at low prevalence? Surprisingly, error rates were significantly greater at 2% target prevalence (∼14%) than at 50% (∼2.5%), demonstrating that participants miss even obvious targets if they are infrequent. In a second experiment, we forced participants to wait a minimum duration before responding. This effort to reduce possible speed-accuracy trade-offs reduced miss errors at low prevalence (∼5%), although this rate was still higher than in 50% prevalence minimum exposure conditions (∼2%). Thus, low prevalence can induce observers to miss highly salient targets and speed-accuracy trade-offs account for most but not all of this effect.

Rich, A. Kunar, M. Van Wert, M. Hidalgo-Sotelo, B. Wolfe, J. (2007). Do rare features pop out? Exploring the boundaries of the low prevalence effect [Abstract]. Journal of Vision, 7(9):708, 708a, http://journalofvision.org/7/9/708/, doi:10.1167/7.9.708. [CrossRef]
Footnotes
 ANR is supported by NHMRC & R.G. Menzies Fellowships (Australia)
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