Arousing auditory stimulus improves performance in a discriminative reaction time task

Arousal reflects a state of generalized physiological activation closely related to a variety of phenomena such as attention and motivation. Reaction times (RT) represent an indirect measure of arousal, and in a condition of increased arousal it has been showed a reduction of RTs, denoting a performance improvement. Hence, the possibility to modulate arousal in order to obtain a better performance could have potential applications in rehabilitation contexts. The aim of the present study was to investigate the effect of an arousing auditory stimulus (brief bursts of white noise presented to a volume of 90 decibel, able to induce a startle reflex) during a discriminative RT task. Twenty healthy volunteers (15 females, mean age 27.3) participated in the experiment. The task was a continuative quasi-random visual presentation, for 100 ms, of digits from 1 to 9, with a variable inter-trial interval of 800-2000 ms. In the first condition of the task, subjects had to press response buttons for target digits (8-9) which were presented after a warning digit (1). In the second condition, during the same task a burst of white noise was presented to the subject through headphones concurrently to the presentation of the warning digit. The order of the two conditions was balanced between subjects. Results showed a significative interaction between the condition and the order of presentation (p = .006), with a steep reduction of RTs in the subjects who heard the arousing stimuli in the second part of the task. Subjects who heard the arousing stimuli in the first part of the task didn’t show any difference between the two conditions, with reduced RTs already from the beginning. In the light of these results it is possible to conclude that the arousing auditory stimulus improved the performance of the subjects during its presentation and in the following part of the task, due to an increased arousal maintained over time. It is also feasible that the arousing stimulus strengthened a possible learning effect between stimulus and response.