Abstract
Visual estimation of numerosity involves the discrimination of magnitude between two distributions or perceptual sets that vary in number of elements. How performance on such estimation depends on peripheral sensory stimulation is unclear, even in typically developing adults. Here, we varied the central and surround contrast of stimuli that comprised a visual estimation task in order to determine whether mechanisms involved with the removal of unessential visual input functionally contributes toward number acuity. The visual estimation judgments of typically developed adults were significantly impaired for high but not low contrast surround stimulus conditions. The center and surround contrasts of the stimuli also differentially affected the accuracy of numerosity estimation depending on whether fewer or more dots were presented. Remarkably, observers demonstrated the highest mean percentage accuracy across stimulus conditions in the discrimination of more elements when the surround contrast was low and the background luminance of the central region containing the elements was dark (black center). Conversely, accuracy was severely impaired during the discrimination of fewer elements when the surround contrast was high and the background luminance of the central region was mid level (gray center). These findings suggest that estimation ability is functionally related to the quality of low-order filtration of unessential visual information. These surround masking results may help understanding of the poor visual estimation ability commonly observed in developmental dyscalculia.
Highlights
The effect of peripheral visual stimulation, varying in contrast and or luminance, on the ability to make numerosity estimation judgments of centrally presented elements, has seldom been investigated in typically developing adults
Post hoc comparisons for this interaction revealed that the mean proportion of correct responses (PCR) for estimating less dots in the presence of the low contrast surround, was significantly lower than estimating more dots under the same surround contrast conditions [t(15) = 2.38, p = 0.002]
Under the high contrast surround condition the mean PCR for estimation of more dots was significantly lower than estimation of less dots [t(15) = 3.68, p = 0.031]
Summary
The effect of peripheral visual stimulation, varying in contrast and or luminance, on the ability to make numerosity estimation judgments of centrally presented elements, has seldom been investigated in typically developing adults. The process of visual estimation involves the discrimination of magnitude between two distributions or perceptual sets that vary in number of elements. Peripheral visual stimulation at high sensory load deleteriously affects such discrimination. One of the earliest (and most influential) investigations into the effects of surround-masking (Chubb et al, 1989) revealed that the perceptual contrast of a central texture region became much lower when enveloped by a high contrast surround
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