Dissociation of perceived size and perceived strength in the scintillating grid illusion

ImageNet-trained deep neural networks exhibit illusion-like response to the Scintillating grid

Deep neural network (DNN) models for computer vision are capable of human-level object recognition. Consequently, similarities between DNN and human vision are of interest. Here, we characterize DNN representations of Scintillating grid visual illusion images in which white disks are perceived to be partially black. Specifically, we use VGG-19 and ResNet-101 DNN models that were trained for image classification and consider the representational dissimilarity (\(L^1\) distance in the penultimate layer) between pairs of images: one with white Scintillating grid disks and the other with disks of decreasing luminance levels. Results showed a nonmonotonic relation, such that decreasing disk luminance led to an increase and subsequently a decrease in representational dissimilarity. That is, the Scintillating grid image with white disks was closer, in terms of the representation, to images with black disks than images with gray disks. In control nonillusion images, such nonmonotonicity was rare. These results suggest that nonmonotonicity in a deep computational representation is a potential test for illusion-like response geometry in DNN models.

Scintillating Grid Illusion Without the Grid

The scintillating grid illusion is a phenomenon where illusory black spots are perceived on white patches located at the intersections of a grid pattern. In this study, I report that the illusory spots as observed in the illusion are perceived with a stimulus pattern without grid bars. In two experiments, I investigated the perceptual properties of the scintillating illusion without grid bars. I found that the strength of the illusion depends on the contour shape of the patch components as in the scintillating grid illusion, while neither the density nor spatial alignment largely affect the illusory percepts. These findings undermine the previous theories on the mechanism of the scintillating grid illusion, as it was assumed that the grid bars are the essential component to induce the illusion. The results suggest that the illusory spots of the scintillating grid illusion could be induced by the limited processing of the patch stimuli in the peripheral vision and that the grid could play a supplementary role by enhancing the effect by further interfering with the processing.