June 2007
Volume 7, Issue 9
Free
Vision Sciences Society Annual Meeting Abstract  |   June 2007
Dividing attention between multiple targets: simultaneous or sequential allocation?
Author Affiliations
  • Rufin VanRullen
    CerCo, CNRS, Université Paul Sabatier Toulouse 3, and Department of Psychology, Harvard University
  • Thomas Carlson
    Department of Psychology, Harvard University
  • Patrick Cavanagh
    Department of Psychology, Harvard University, and Laboratoire de Psychologie de la Perception, Université Paris V
Journal of Vision June 2007, Vol.7, 642. doi:10.1167/7.9.642
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      Rufin VanRullen, Thomas Carlson, Patrick Cavanagh; Dividing attention between multiple targets: simultaneous or sequential allocation?. Journal of Vision 2007;7(9):642. doi: 10.1167/7.9.642.

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

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Abstract

Increasing evidence suggests that attention can concurrently select multiple locations; yet it is not clear whether this ability relies on continuous allocation of attention to the different targets (a “parallel” strategy), or whether attention switches rapidly between the targets (a temporal “sampling” strategy). Indeed, both strategies can explain the occurrence of classic “set size effects” (i.e. decreases of performance with increasing number of attended items), either because attention is a limited resource (“parallel” strategy), or because the effective time that attention samples each object decreases when several objects must be attended (“sampling” strategy). However, the psychometric function for detection of a single target as a function of its duration can be used to predict the expected psychometric function for multiple targets, and the predicted shape is quite different for parallel and sequential strategies. We find that the model that best predicts our observed data is a “sampling” model when the task involves a challenging contrast decrement detection (with the sampling period around 140ms, ranging from 100ms to 180ms across our 8 subjects), whereas the optimal model is a “parallel” one for an easy version of the same task (with a performance loss of 16% for each additional item to be attended). This distinction was observed for all subjects tested. The two versions of the task give rise, respectively, to serial (40ms/item) and parallel (0ms/item) slopes in a visual search situation. The results suggest that, at least for attentionally demanding tasks, it may not be possible to simultaneously attend to multiple locations; instead, the multiple items of interest are processed in series at a rate of about 7 items per second.

VanRullen, R. Carlson, T. Cavanagh, P. (2007). Dividing attention between multiple targets: simultaneous or sequential allocation? [Abstract]. Journal of Vision, 7(9):642, 642a, http://journalofvision.org/7/9/642/, doi:10.1167/7.9.642. [CrossRef]
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