Exploring the effect of transient cognitive load on bodily arousal and secondary task performance

Human failure constitutes a major cause for accidents of all kinds. Especially drowsiness or situations of cognitive overload impair the ability to react quickly and appropriately to critical events. The present study applies brief periods of monotonous and repetitive trains of thoughts to induce states of hypovigilance and, on the other hand, arithmetical exercises to increase cognitive load. Aim is to determine whether transient cognitive events exert an influence on bodily arousal (here: pupil diameter) as well as on secondary task reaction times. Findings confirm that pupil diameter constitutes a valid indicator of cognitive load. Reaction times emerge particularly slow during high cognitive load, whereas the risk of overlooking brief cue stimuli is not increased. However, it remains unclear whether a valid state of cognitive underload can be induced on basis of short periods of repetitive thoughts. While the associated pupil size changes do not differ from baseline dynamics, motor reactions occur considerably slower compared to a control condition.