Abstract
Numerosity perception is a process involving several stages of visual processing. This study investigated whether distinct mechanisms exist in numerosity adaptation under different awareness conditions to characterize how numerosity perception occurs at each stage. The status of awareness was controlled by masking conditions, in which monoptic and dichoptic masking were proposed to influence different levels of processing. Numerosity adaptation showed significant aftereffects when the participants were aware (monoptic masking) and unaware (dichoptic masking) of adaptors. The interocular transfer for numerosity adaptation was distinct under the different awareness conditions. Adaptation was primarily binocular when participants were aware of stimuli and was purely monocular when participants were unaware of adaptors. Moreover, numerosity adaptation was significantly reduced when the adaptor dots were clustered into chunks with awareness, whereas clustering had no effect on unaware adaptation. These results show that distinct mechanisms exist in numerosity processing under different awareness conditions. It is suggested that awareness is crucial to numerosity cognition. With awareness, grouping (by clustering) influences numerosity coding through altered object representations, which involves higher-level cognitive processing.
Highlights
Numeracy is founded upon a non-symbolic system of numerical representation, at the heart of which is the ability to perceive and discriminate numerosities [1]
The values of the test stimuli (X axis) corresponding to the 50% points were calculated from the fitted curves. These values were point of subjective equality (PSE) representing the number of test dots, which appeared to equal the number of probe dots for participants
The change in numerosity perception in the tests can be demonstrated by the difference in the average values for PSEs under different conditions (Table 1)
Summary
Numeracy is founded upon a non-symbolic system of numerical representation, at the heart of which is the ability to perceive and discriminate numerosities [1]. Numerosity estimation is proposed to be accompanied by processes for a combination of “surrogate” features that approximate a number [3], such as total area, spatial frequency, and texture density [4,5,6,7]. It should connect to other representations of magnitude This perspective is supported by the fact that nonnumerical cues can affect number processing [4,13]. Changing the features of distributions of stimulus dots (e.g., when dots clustered together) profoundly decreases the perceived numerosity [4,13]. This result holds when dots are connected by lines [3,14]
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