A visual sense of number.

SummaryEvidence exists for a nonverbal capacity for the apprehension of number, in humans [1] (including infants [2, 3]) and in other primates [4–6]. Here, we show that perceived numerosity is susceptible to adaptation, like primary visual properties of a scene, such as color, contrast, size, and speed. Apparent numerosity was decreased by adaptation to large numbers of dots and increased by adaptation to small numbers, the effect depending entirely on the numerosity of the adaptor, not on contrast, size, orientation, or pixel density, and occurring with very low adaptor contrasts. We suggest that the visual system has the capacity to estimate numerosity and that it is an independent primary visual property, not reducible to others like spatial frequency or density of texture [7]

The ventriloquist effect results from near-optimal bimodal integration

Results for the various unimodal location discriminations for naive observer L.M. are shown in Figure 1A. The curves plot the proportion of trials in which the second stimulus was seen to the left of the first, as a function of actual physical displacement. Following standard practice, the data were fitted with cumulative Gaussian functions free to vary in position and width: the position of the median (50 % leftward) is termed the point of subjective equality (PSE), and the width � 3Department of Psychology represents the estimate of localization accuracy (pre-University of Florence sumed to depend on internal noise). For all unimodal 50125 Florence conditions, the PSE was near 0�, but � varied consider-Italy ably. For visual stimuli, � was smallest (approximatel

constructing stable spatial maps of the word

To interact rapidly and effectively with our environment, our brain needs access to a neural representation—or map—of the spatial layout of the external world. However, the construction of such a map poses major challenges to the visual system, given that the images on our retinae depend on where the eyes are looking, and shift each time we move our eyes, head, and body to explore the world. Much research has been devoted to how the stability is achieved, with the debate often polarized between the utility of spatiotopic maps (that remain solid in external coordinates), as opposed to transiently updated retinotopic maps. Our research suggests that the visual system uses both strategies to maintain stability. f MRI, motion-adaptation, and saccade-adaptation studies demonstrate and characterize spatiotopic neural maps within the dorsal visual stream that remain solid in external rather than retinal coordinates. However, the construction of these maps takes time (up to 500 ms) and attentional resources. To s..