The accessory stimulus effect is mediated by phasic arousal: A pupillometry study

TY - JOUR

T1 - The accessory stimulus effect is mediated by phasic arousal: A pupillometry study

AU - Tona, Klodiana-Daphne

AU - Murphy, Peter

AU - Brown, Stephen

AU - Nieuwenhuis, Sander

PY - 2016/4/1

Y1 - 2016/4/1

N2 - People usually respond faster to a visual stimulus when it is immediately preceded by a task-irrelevant, auditoryaccessory stimulus (AS). This AS effect occurs even in choice reaction time tasks, despite the fact that the AS carriesno information about the correct response. Researchers often assume that the AS effect is mediated by a phasic arousalburst evoked by the AS, but direct evidence for that assumption is lacking. We conducted a pupillometry study todirectly test the phasic arousal hypothesis. Participants carried out a demanding choice reaction time task withaccessory stimuli occurring on 25% of the trials. Pupil diameter, a common index of arousal, was measured throughoutthe task. Standard analyses of task performance and pupil diameter showed that participants exhibited the typical ASeffect, and that accessory stimuli evoked a reliable early pupil dilation on top of the more protracted dilationassociated with the imperative stimulus. Moreover, regression analyses at the single-trial level showed that variation inreaction times on AS trials was selectively associated with pupil dilation during the early time window within whichthe AS had an effect, such that particularly large AS-evoked dilations were associated with especially fast responses.These results provide the first evidence that the AS effect is mediated by AS-evoked phasic arousal.

AB - People usually respond faster to a visual stimulus when it is immediately preceded by a task-irrelevant, auditoryaccessory stimulus (AS). This AS effect occurs even in choice reaction time tasks, despite the fact that the AS carriesno information about the correct response. Researchers often assume that the AS effect is mediated by a phasic arousalburst evoked by the AS, but direct evidence for that assumption is lacking. We conducted a pupillometry study todirectly test the phasic arousal hypothesis. Participants carried out a demanding choice reaction time task withaccessory stimuli occurring on 25% of the trials. Pupil diameter, a common index of arousal, was measured throughoutthe task. Standard analyses of task performance and pupil diameter showed that participants exhibited the typical ASeffect, and that accessory stimuli evoked a reliable early pupil dilation on top of the more protracted dilationassociated with the imperative stimulus. Moreover, regression analyses at the single-trial level showed that variation inreaction times on AS trials was selectively associated with pupil dilation during the early time window within whichthe AS had an effect, such that particularly large AS-evoked dilations were associated with especially fast responses.These results provide the first evidence that the AS effect is mediated by AS-evoked phasic arousal.

U2 - 10.1111/psyp.12653

DO - 10.1111/psyp.12653

M3 - SCORING: Journal article

VL - 53

SP - 1108

EP - 1113

JO - PSYCHOPHYSIOLOGY

JF - PSYCHOPHYSIOLOGY

SN - 0048-5772

IS - 7

ER -