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George Alvarez, Steven Franconeri; Rapid enumeration is based on a segmented visual scene. Journal of Vision 2009;9(8):14. doi: 10.1167/9.8.14.
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© ARVO (1962-2015); The Authors (2016-present)
How do we estimate the number of objects in a set? One primary question is whether our estimates are based on an unbroken visual image or a segmented collection of discrete objects. We manipulated whether individual objects were isolated from each other, or grouped into pairs by irrelevant lines. If number estimation operates over an unbroken image, then this manipulation should not affect estimates. But if number estimation relies on a segmented image, then grouping pairs of objects into single units should lead to lower estimates. In Experiment 1, participants underestimated the number of grouped squares, relative to when the connecting lines were ‘broken’. Experiment 2 presents evidence that this segmentation process occurred broadly across the entire set of objects. In Experiment 3, a staircase procedure provides a quantitative measure of the underestimation effect. Experiment 4 shows that is the strength of the grouping effect was equally strong for a single thin line, and the effect can be eliminated by a tiny break in the line. These results provide the first direct evidence that number estimation relies on a segmented input.
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