CUED Publications database

Independence is elusive: set size effects on encoding precision in visual search.

Mazyar, H and van den Berg, R and Seilheimer, RL and Ma, WJ (2013) Independence is elusive: set size effects on encoding precision in visual search. J Vis, 13.

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Looking for a target in a visual scene becomes more difficult as the number of stimuli increases. In a signal detection theory view, this is due to the cumulative effect of noise in the encoding of the distractors, and potentially on top of that, to an increase of the noise (i.e., a decrease of precision) per stimulus with set size, reflecting divided attention. It has long been argued that human visual search behavior can be accounted for by the first factor alone. While such an account seems to be adequate for search tasks in which all distractors have the same, known feature value (i.e., are maximally predictable), we recently found a clear effect of set size on encoding precision when distractors are drawn from a uniform distribution (i.e., when they are maximally unpredictable). Here we interpolate between these two extreme cases to examine which of both conclusions holds more generally as distractor statistics are varied. In one experiment, we vary the level of distractor heterogeneity; in another we dissociate distractor homogeneity from predictability. In all conditions in both experiments, we found a strong decrease of precision with increasing set size, suggesting that precision being independent of set size is the exception rather than the rule.

Item Type: Article
Uncontrolled Keywords: Analysis of Variance Attention Discrimination (Psychology) Female Form Perception Humans Male Models, Theoretical Photic Stimulation Signal Detection, Psychological Size Perception Visual Perception
Divisions: Div F > Computational and Biological Learning
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:14
Last Modified: 21 Jun 2018 02:37