Phasic heart rate change and the U-shaped relationship between choice reaction time and auditory signal intensity.

Abstract

ABSTRACTThe effect of auditory intensity on choice reaction time (RT) and heart rate (HR) was studied in two experiments using a 2.5‐sec fixed foreperiod paradigm and a mixed block intensity presentation mode. Experiment I showed a U‐shaped RT/intensity function and a triphasic HR response. However, the usually obtained anticipatory HR deceleration did not appear. There was only a slight deceleration after the onset of the imperative signal. Both strong tones and faster responding were associated with a more rapid shift from less deceleration to more acceleratory recovery. A second experiment produced similar findings. In addition, differential warning with respect to signal intensity reduced its effect on RT and accelerated the HR response to the imperative signal. The triphasic HR response disappeared in reaction to a “No‐Go” warning signal instructing the subject to withhold his motor response to the imperative signal. It was argued that, apart from being an input variable, auditory intensity has an additional effect upon the motor system. It was concluded that this immediate arousal effect of loud auditory signals (Sanders, 1977) could be related to Graham's (1980) notion of defense as primarily a motor facilitating system.Finally, the finding of a consistent relationship between fast reactions and less deceleration together with the absence of the anticipatory deceleration clearly does not fit either the Obrist model or the Lacey model.