Distinct Contributions of Genes and Environment to Visual Size Illusion and the Underlying Neural Mechanism

Abstract

As exemplified by the Ebbinghaus illusion, the perceived size of an object can be significantly biased by its surrounding context. The phenomenon is experienced by humans as well as other species, hence likely evolutionarily adaptive. Here, we examined the heritability of the Ebbinghaus illusion using a combination of the classic twin method and multichannel functional near-infrared spectroscopy. Results show that genes account for over 50% of the variance in the strength of the experienced illusion. Interestingly, activations evoked by the Ebbinghaus stimuli in the early visual cortex are explained by genetic factors whereas those in the posterior temporal cortex are explained by environmental factors. In parallel, the feedforward functional connectivity between the occipital cortex and the temporal cortex is modulated by genetic effects whereas the feedback functional connectivity is entirely shaped by environment, despite both being significantly correlated with the strength of the experienced illusion. These findings demonstrate that genetic and environmental factors work in tandem to shape the context-dependent visual size illusion, and shed new light on the links among genes, environment, brain, and subjective experience.

Number comparison under the Ebbinghaus illusion

“…The illusion magnitude is defined as the diameter difference between the center patches surrounded by small and large inducers, compared to the standard patch size (Takao et al, 2021 ). The overall illusion magnitude is 25% for random patterns (2.2°), and 23% for regular patterns(2.0°), which is in accordance with the related studies (Chen et al, 2021 ; Takao et al, 2021 ).…”

“…According to a previous study, a mismatch in numerosity caused by the connectedness illusion (He et al, 2009 ) does not result in a bias on the perceived duration, while a mismatch in physical numerosity does affect the perceived duration, suggesting that the influence of numerosity on duration occurs before the connectedness illusion (Togoli et al, 2021 ). The Ebbinghaus illusion, however, is encoded and computed to a large extent along the ventral visual stream, including the early visual cortex like V1 and V2/V3, and the posterior temporal cortex (Chen et al, 2021 ). Thus, the absence of effect cannot be explained as the Ebbinghaus illusion emerges after the processing of numerosity and density.…”

Neuroimaging evidence of visual-vestibular interaction accounting for perceptual mislocalization induced by head rotation

“…Analyses below mainly focused on the change of [HbO] as it is considered a more sensitive measure compared to [HbR] or [tHb] 56 – 58 and many past studies have selected [HbO] as the main analysis target. 34 , 59 – 61 However, the results for [HbR] will also be reported as a comparison.…”