Schedule of Events | Symposia

Neural investigation of color coherence in numerosity perception

Poster Session F - Tuesday, April 1, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Shimin Hu¹ (shiminhu@umass.edu), Joonkoo Park¹; ¹University of Massachusetts Amherst

We recently proposed a hypothesis that numerosity perception arises as a byproduct of a canonical neurocomputational mechanism across the visual stream. According to this view, numerosity is encoded across multiple processing stages, with each stage that is best suited to encode the features represented in the stimulus. Here, we test this hypothesis by investigating the visual-evoked potential (VEP) signatures of the coherence illusion in color. Behaviorally, numerosity of an array of items with heterogeneous colors are underestimated compared with a homogeneous color. As past research in color perception demonstrates the encoding of color in V1, V2, and V4 with distinct temporal signatures, we predicted that VEPs would differ across latencies for homogeneous and heterogeneous colored arrays. Adult participants (N=43) passively viewed dot arrays that systematically varied in number, size, spacing, and color (homogeneous vs. heterogeneous). A linear mixed model was employed to assess the effects of these fixed-effects predictors on the VEP amplitudes in the occipital channels across the time course. The effects of number, size, and spacing on the neural activity replicated previous findings. The effect of color homogeneity was observed across multiple latency periods, in alignment with our hypothesis. Interestingly, the pattern of these effects across time indicated that the underestimation of heterogeneous colored arrays may arise from late (> 250 ms), rather than early processing stages. These results suggest that numerosity information is encoded across multiple perceptual stages and avenues for further investigation into how this information is read out for a unified percept of numerosity.

Topic Area: PERCEPTION & ACTION: Vision