Psychophysiological changes during a VDU repetitive task

Abstract

A simulated realistic data-entry task on a visual display unit (VDU) was employed to study the relationships between performance and various physiological indices of arousal. After several training sessions on separate days, subjects performed the data-entry task which lasted 120 min. All the components of the workplace were adjusted in order to provide each subject with suitable ergonomic conditions. Performance (correct entries, errors, omissions) and physiological parameters (spectral analysis of the electroencephalogram (EEG) and heart rate (HR)) were recorded continuously. Three functional tests were performed before and after the data-entry task: an eye muscle balance test, a visual reaction time task (RT) and an attentional-perceptual task (AP) displayed on the terminal. Data-entry task performance showed a progressive decline, reaching minimal values after 45-60 min of work, followed by a significant rebound. This pattern characterized 80% of the subjects and was not dependent on the individual average level of performance. Behavioural responses were found to be associated with corresponding EEG arousal changes: i.e. with a parallel trend of beta activity and an opposite one of theta and alpha activities, whereas average HR decreased from the beginning to the end. There is some evidence that different EEG frequency bands are more sensitive to selective attentional requirements than HR which is rather related to diffuse arousal changes. The before/after tests showed a more pronounced esophoria, an increase of RT and of errors percentage in the AP task after 2 hours of work. The EEG did not show any significant difference after work but the average HR level was significantly lower compared with the before-work values. The EEG pattern accompanying the rebound of the performance during the data-entry task supports the auto-arousal hypothesis which assumes that a cerebral compensatory effort intervenes in a mental repetitive task.