Abstract
Background
Left-behind children（LBC has experienced parent-child separation, which is a special parent-child separation and social isolation model. Adverse events in early development may have important effects on the development of the nervous system, including the influence on sensory and perceptual cognitive processing, thus increasing the susceptibility to mental illness. Meanwhile, there are various neurological and brain root causes behind left-behind children’s learning difficulties, non-socialization and other psychological behavior problems. In addition, left-behind may have sensory, perceptual and cognitive processing abnormalities. This study tries to elaborate and extract the eye movement characteristics of left-behind children, lay a foundation for the discussion of the mechanism of abnormal visual processing, and provide a scientific basis for follow-up of left-behind children and the early identification, prevention and control of mental diseases.
Methods
The standards for grouping left-behind children are as follows: the children who are separated from both parents 6 months after birth and spend less than 2 months with their parents each month, and the non-left-behind children with matched gender, age and education years, exclusion criteria is: neurological diseases, family history of mental illness, broken family (single parent, bereavement), high myopia (greater than 1000 degrees), eye and eyelash cannot be identified by infrared light. EyeControl portable eye movement tester (built-in infrared, speed: 100Hz, error <0.5°) developed by Qingtech and its software processing system were used. The subjects’ eye movements and various analysis indexes in various tasks were collected. The eye movement indexes of smooth pursuit eye movement, fixation stability and free browsing were collected, so as to investigate the effects of left-behind on static attention retention, visual tracking and face recognition in social scenes.
Results
Among the 175 children, the smooth tracking mean deviation of LBC is significantly increased (P=0.017). The mean deviation of the O and S-curve tracking of the LBC is significantly increased (P=0.018; P=0.034), and the OS curve mean deviation and hyperactivity correlated (r=-0.273, P=0.011). In terms of the time that peak deviation takes (F=4.329, P=0.014), there is significant interaction between the age groups and the left-behind groups. In the social scenes, the first fixation time of face (P=0.039), the number of eye entry count (P=0.020), and the eye fixation time (P=0.003) of LBC are all significantly reduced, and the number of mouth entry count (P=0.007) and the number of fixation (P=0.023) of LBC are all significantly increased. Under the circumstance of low facial processing, there is a significant difference between LBC and NLBC (P=0.009), and that difference is not significant under the circumstance of high facial processing, and there is a significant difference between low facial processing LBC and high facial processing NLBC (P=0.007).
Discussion
Left-behind children have obstacles in dynamic visual information processing, insufficient inhibition and control, and poor cognitive flexibility, which may be related to hyperactivity. The attention retention in visual tracking decreased with the increase of age. Left-behind children have difficulties in face recognition in social scenes. In the case of low facial processing, left-behind children aggravated the defects of speech comprehension, while in the case of high facial processing, left-behind children had no significant influence on speech comprehension. Therefore, we should intervene the left-behind children in the early days, and this study provides a scientific basis for the formulation of social policies.
Comparing Face and Object Processing in Perception and Recognition