Vision is one of the most important senses for human to obtain information from the outside world, in which visual motion perception is very important to realize the dynamic interaction between human and the external environment. So, it is of great significance to explore the neural mechanism of visual motion perception. The relationship between sensory measurement and intelligence had been widely discussed in recent years. It linked high level cognitive function with low level sensory and perceptual processing, which may suggest that higher cognitive factors may have impact on basic visual processing. Therefore, the first study used the method of individual difference to investigate the relationship between visual motion processing and individual intelligence level. Hunter-gatherer hypothesis proposed that men and women differing in some functions are caused by different division of labor in early primitive society. Males showed an advantage in visual processing related to space and motion, while females performed better on object and face discrimination tasks. These may suggest that there may exist gender differences in two visual pathways. Therefore, the second study used the different types of visual motion tasks to examine whether there are gender differences in motion processing supported by the visual dorsal pathway. These two studies had important implications for our understanding of visual motion perception from different perspectives.
Study 1 consisted of three experiments to investigate the relationship between visual motion processing and intelligence. In Experiment 1, we used motion detection task and motion discrimination task and found that the visual tasks without inhibition was not related to the individual's intelligence score. In Experiment 2, we used the motion surround suppression task and found that surround suppression effect was negatively correlated with the intelligence score. In Experiment 3, we used motion adaptation paradigm and found that temporal suppression effect was not related to intelligence level. Therefore, intelligence level can predict spatial suppression effect but not temporal suppression effect. The surround suppression and motion aftereffect may reflect different neural mechanisms.
Study 2 included two experiments to investigate whether gender differences existed in visual motion processing. In Experiment 4, we used motion detection task and motion discrimination task composed of random dot kinematograms (RDK), and found that there were no significant gender differences in threshold and accuracy, but there were significant gender differences in reaction time. In Experiment 5, we adopted surround suppression task composed of grating stimuli and found that males tended to have lower thresholds than females at high contrast condition, and the difference was most significant when stimulus size was small.
In conclusion, spatial suppression reflected in the surround suppression task was related to intelligence, but could not be generalized to the task involving temporal suppression effect, suggesting that the relationship between higher intelligence and visual processing was limited to specific tasks. There was no significant gender difference in the motion tasks composed of RDK stimuli, while males performed better than females in the grating orientation judgment with high contrast. This suggests that we should pay attention to the influence of different tasks and types of stimuli on the results of gender difference in visual motion studies. In relevant visual studies, researchers should consider gender factor in experiment design and data analysis.
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