Assessment of affect and brain-behavioral systems based on cycle of morningness and eveningness

Biological aspects of personality have an important influence on people psychological dimensions. People affective and mood states can be changed based on cycle of Hostelry. The aim of the present study was to investigate negative/positive affect levels and reinforcement sensitivity based on the change in the circadian cycle morningness and eveningness. First, 600 students (316 girls, 284 boys) from the University of Urmia participated in the study. Participants completed the Morningness-Eveningness Questionnaire (MEQ). Then, 83 participants were selected for the second stage according to obtained scores in MEQ, as morningness, eveningness, and intermediate individuals. Finally, participants completed the Positive and Negative Affect Schedule (PANAS) and the Behavioral Activation System (BAS) and Behavioral Inhibition System (BIS) Scales. Results indicated significant differences among dimensions of positive and negative affect based on the types of morningness, eveningness, and intermediate types. The morningness type had a higher positive affect and lower negative affect. Comparison of morningness and eveningness types in the biological aspects of personality including behavioral activation and behavioral inhibition showed no significant difference between the two groups. Based on the study results, this can be concluded that individual differences in experience of positive and negative affect can be caused by changes associated with circadian cycles.