The dynamics of grouping-induced biases in apparent numerosity revealed by a continuous tracking technique

Connecting pairs of items causes robust underestimation of the numerosity of an ensemble, presumably by invoking grouping mechanisms. Here we asked whether this underestimation in numerosity judgments could be revealed and further explored by continuous tracking, a newly developed technique that all...

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Bibliographic Details
Published in:Journal of vision (Charlottesville, Va.) Va.), 2021-12, Vol.21 (13), p.8-8
Main Authors: Ambrosi, Pierfrancesco, Pomè, Antonella, Burr, David Charles
Format: Article
Language:English
Subjects:
Bias
Humans
Judgment
Pattern Recognition, Visual
Psychophysics
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Summary:Connecting pairs of items causes robust underestimation of the numerosity of an ensemble, presumably by invoking grouping mechanisms. Here we asked whether this underestimation in numerosity judgments could be revealed and further explored by continuous tracking, a newly developed technique that allows for fast and efficient data acquisition and monitors the dynamics of the responses. Participants continuously reproduced the perceived numerosity of a cloud of dots by moving a cursor along a number line, while the number of dots and the proportion connected by lines varied over time following two independent random walks. The technique was robust and efficient, and correlated well with results obtained with a standard psychophysics task. Connecting objects with lines caused an underestimation of approximately 15% during tracking, agreeing with previous studies. The response to the lines was slower than the response to the physical numerosity, with a delay of approximately 150 ms, suggesting that this extra time is necessary for processing the grouping effect.
ISSN:1534-7362
1534-7362
DOI:10.1167/jov.21.13.8