Investigating the expression of the acoustic intensity effect in cognitive tasks involving perceptual and visuomotor control

Abstract

The main objective of our research project was to understand which mechanisms are triggered by the accessory characteristics of an acoustic WS, in particular its intensity, and the temporal information provided by the presentation of a WS, and how these mechanisms can modulate the processing of target and the response motor preparation. For this reason, we designed three experimental series, which allowed us to investigate in an optimal way the influences of the characteristics of WSs on the attentional mechanisms of alertness and cognitive control, as well as on the visual search for the target. To investigate the role of response preparation (derived from the temporal information provided by the WS) and to understand the impact of the WS intensity level were our main objectives of the Experimental Series 1. Our main idea was that the WS could influence response times because of the temporal information about the presentation of the target, of an automatic acceleration of the response due to the intensity effect, or of the influence of both mechanisms. We studied these two factors by manipulating on the one hand the simultaneity between WS and target, and on the other hand the intensity of the WS. Knowing that a very intense sound can trigger a defensive motor response, called startle reflex (Carlsen, 2011), we differentiated between trials with a startle response and those without a startle response. We also study whether the intensity effect is influenced by the level of control demand of the task. The pure alerting effect leads to an automatic acceleration of the direct response of target stimuli. This results in an acceleration of responses, but especially when there is only one target, and when the direct and automatic response to it is the correct one. However, in conditions where it is not clear which stimulus is the target, or when it appears between distracting information, or the correct response to the target is not the most automatic and direct one, the increased intensity of the WS has a negative effect, by facilitating the automatic distracting response, or the selection of a distracter instead of the target. In these situations, the activated response, or the initial selection, must be inhibited, which finally leads to a loss of the initial alerting advantage, or even to a detrimental effect, that lead to a slower response.