Comparison of Visual Perception, Processing Speed and Sustained Attention in Circadian Cycles of Normal Students (both girls and boys) and also Students with and without Special Learning Disorders

The present study was conducted to compare changes in visual perception, processing speed and sustained attention at different times of the day in normal students and students with special learning disorders in a range of 8-12 years of old according to chronobiology principles.

The goal of this research was practical and its procedure was non-experimental and post-event one. Statistical community consisted of all students in range of 8-12 years of old elementary school students of Districts 13,14,15 of Tehran Province in academic years of 2018-2019 and 2019-2020. Sample size included 232 students who were selected through available sampling and then in the next stage through multi-stage random selection from which 115 students had learning disorders (55 girls and 60 boys) and 117 were normal students (60 girls and 57 boys). Sample size according to the type of dependent and independent variables (visual perception, processing speed and sustained attention; continuous quantification and circadian cycles; multi-valued class) and causal-comparative research method, was assumed at least 15 students for each group. Because of the probability of losing the number of samples in each subgroup; approximately 60 students were considered as girls and boys with or without learning disabilities. Then, each group of normal students and students with learning disorders, (both girls and boys), were divided into four groups of 60, and each group is participated in four rounds of visual skills perception test, integrated auditory-visual function test, intelligence processing speed subtests and Wexler (symbolization and encryption) test respectively. The results of this study were analyzed by Multivariate Analysis of variance test in SPSS software version 22 in order to determine a significant difference between several completely independent samples.

Visual perception of the group with and without learning disorders in various hours of a day showed a significant difference. Visual perception in the group of normal students was higher than students with learning disabilities. The degree of memory components of visual sequence, spatial perception of vision and perception of stability of visual form in the afternoon was more than that degree in the morning. In addition, the processing speed of girls in the symbolization component was significantly higher than that level in boys. The highest average processing speed in all groups was observed between 13.45p.m to 14.15 p.m. Also sustained attention was significantly higher than students with learning disorders and the highest average of sustained visual and auditory attention was observed through 13.45p.m to 14.15p.m. Female students were identified with a higher average of sustained attention than male students, although this difference Level was not significant.

In general, the findings of this study showed that some factors should be considered in students' curriculum such as Gender, daylight hours, minimum and maximum hours of cognitive indicators based on natural fluctuations in order to boost the efficiency of their mental abilities. Also, other factors such as morning and evening, sleep and wake up time cycle and nutritional agents and etc. should be considered as marginal effects on students' abilities.