The study of perception and interaction with illusory objects allows for the assessment of visual perception subsystems under both standard and unusual conditions. In this series, we investigated changes in the strength of the vertical-horizontal illusion (VHI) under Dry Immersion (DI) conditions. Data on verbal and motor assessments of VHI were obtained from a group of eight subjects undergoing 15 days of DI. The method of adjustment was used for verbal assessment, while the tracking method, which includes memorization and reproduction of the stimulus, was used for motor assessment. At each stage, 20 stimuli (an inverted letter T) of five different lengths were presented in random order at the center of a sensory screen. Measurements were conducted before DI (Baseline), on the 1st, 3rd, 5th, 7th, 10th, and 15th days of DI (DI1, DI3, DI5, DI7, DI15), and after its completion (R + 1). The results show that both verbal and motor assessments of VHI significantly depend on the duration of exposure. The strength of VHI in verbal assessment was different from zero at Baseline, DI1, and R + 1. The strength of VHI in motor assessment during the memorization phase was different from zero at DI15 and R + 1. High, significant correlations were observed between the strength of VHI in different types of motor assessments but not between motor and verbal assessments. These findings support the theory of two visual streams, one for perception and one for action.
Lyakhovetskii et al. (Mon,) studied this question.