Biological action identification does not require early visual input for development

Abstract

Visual input during developmental years is vital for the maturity of numerous visual functions. Previous reports have shown that, while normal development of global motion perception seems to require visual input during an early sensitive period, biological motion detection does not seem to do so. A more complex form of biological motion processing is the identification of human actions. Here we tested whether the identification rather than detection of biological motion is experience dependent. A group of human participants who had been treated for partially long lasting congenital cataract (up to 14 years, CC group) had to identify ten actions performed by human line figures. In addition they performed a coherent motion detection task (CM task), which required to identify the direction of coherent motion amidst the movement of random dots. As controls, individuals with developmental cataracts were included to control for the timing of the visual deprivation. Moreover, normally sighted controls were tested both with vision blurred to match the visual acuity of the CC individuals (vision matched group) and with full sight (sighted controls group). The CC group identified biological actions with an extraordinary high accuracy (~85%) and was indistinguishable from the vision matched group. By contrast, coherent motion processing impairments of the CC group persisted even after controlling for visual acuity. These results in the same individuals demonstrate an impressive resilience of biological motion processing to aberrant early visual experience and at the same time a sensitive period for the development of global motion processing in early ontogeny.