Is elicitation of the autonomic orienting response associated with allocation of processing resources?

Two experiments investigated whether elicitation of the autonomic orienting response is associated with active allocation of processing resources as indexed by the slowing of reaction time to secondary task probes. In Experiment 1, 75 college student subjects performed a dual task consisting of a primary auditory orienting task and a concurrent secondary visual reaction time task. The primary orienting task included task-relevant tones presented to one ear and task-irrelevant tones presented to the other ear. The last trial of the primary task included an unexpected novel tone presented binaurally. The secondary task consisted of a series of brief light flashes presented at critical times throughout the primary task; the reaction time of the subjects' motor responses to these flashes was measured. Consistent with the resource allocation view of orienting, the results demonstrated that resources were allocated during the primary task tones and the novel tone, and this allocation was greater during the early trials than the late trials of the primary task. However, a directional dissociation was observed in that resource allocation was greater during the task-irrelevant tone whereas autonomic orienting responses were larger to the task-relevant tone. Experiment 2 replicated all of these effects and demonstrated that the directional dissociation was sensitive to the predictability and ease of discrimination between the task-relevant and task-irrelevant tones. Taken together, these findings indicate that the relationship between resource allocation and autonomic orienting is a reliable but complex one in need of further research.