Objectives: The aims of the study were to investigate the systematic classification of subsidiary behaviors during visual display terminal (VDT) work and discuss the interpretation of these behaviors through an interactive model of subsidiary behaviors, work performance and autonomic nerve activity.
Methods: Twelve university students were instructed to perform continuous 120-min English transcription tasks in a sedentary posture. Data on subsidiary behaviors, work performance (mean keystroke and mean error rates), and autonomic nervous system balance (log-transformed low frequency (LF) / high frequency (HF) ratio) were recorded every 5 min during VDT work.
Results: The subsidiary behaviors were categorized into 3 qualitatively independent factors: distractive behaviors against monotony (DBM), sleepiness-related behaviors (SRB), and habitual behaviors (HB). A cross-correlation analysis indicated that an increase of DBM, which is considered as a sign of workers' attempt to escape from monotonous task operations, was related to a decline in performance. A decrease in the LF/HF ratio was followed by SRB after 5 min passed (r=-0.57, p<0.05), eventually leading to a restriction of the deterioration in performance. An increase of DBM was predictive of an increase in errors (r=0.54, p<0.05), and a significant negative correlation (r=-0.46, p<0.05) between HB and autonomic nerve activity at 10 min after the appearance of HB was observed.
Conclusion: It emerged from the results that the factor structure of subsidiary behaviors consists of 3 mutually independent factors. The interactive model suggests that subsidiary behaviors are possibly precursory signs of errors and changes in autonomic nervous system balance.