Numerosity depends on normalized contrast energy: Review and square-root law model
Lei, Quan Reeves, Adam
Lei, Quan
Reeves, Adam
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2023-10
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Contrast energy,Model,Numerosity discrimination,Numerosity judgement,Numerosity perception,Square root law
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Quan Lei, Adam Reeves (2023). Numerosity depends on normalized contrast energy: Review and square-root law model. Vision Research, Volume 211, 2023, 108280.
Abstract
The perceived numerosity of many randomly-located items of fixed contrast depends on the integrated contrast energy (CE) of the display. We show here that a model based on ?(CE), normalized by contrast amplitude, can fit numerosity judgment data in various tasks and over a wide range of numerosities. The model shows that judged numerosity increases linearly with ?(N), where N is the number of displayed items above the subitization range, and can explain: 1) the general underestimation in absolute judgement of numerosity; 2) the contrast independence (constancy) of numerosity judgment in segregated displays, i.e., judged numerosities are not affected by item contrast; 2) a contrast-dependent illusion where the numerosity of higher-contrast items is further underestimated when intermingled with lower-contrast items; and 3) both the threshold and sensitivity of numerosity discrimination between displays of N and M items. The nearly perfect fit of numerosity judgment data by a square-root law over a wide range of numerosities, including the range typically described by Weber's law, but excluding subitization, suggests that normalized contrast energy might be the prevailing sensory code underlying numerosity perception. ©2023 Elsevier Ltd
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Elsevier Ltd
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Vision Research
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0042-6989