The influence of sensory noise, confidence judgments, and accuracy on pupil responses and trial-by-trial reaction time adjustments in young and older people

Decision confidence and the engagement of pupil-linked arousal systems during perceptual decision-making modulate subsequent behavioural adjustments important for optimal performance. In this study, we investigated if the association between pupil responses, decision confidence and decision accuracy was altered in older adults and if these were related to trial-by-trial reaction time adjustments.

We tested young and older adults, including men and women, with a dot motion discrimination task, while measuring task-related pupil responses. Auditory feedback was provided after each trial. Participants were instructed to report perceived motion direction and simultaneously their decision confidence.

Confidence judgments of both age groups followed the typical signatures of decision confidence. However, older adults were overconfident in the presence of high sensory noise and negative feedback. Interactions between sensory noise, confidence judgments and accuracy revealed blunted pupil responses to performance lapses and negative feedback in older people. In young adults, low confidence in response to high internal noise evoked larger pupil responses than low confidence to high external noise and was associated with higher reaction time adjustments. These effects were reduced in older people. Low confidence responses and errors were associated with slower responses on the subsequent trial in an additive manner with the effect of errors being stronger in the older group. Pupil responses before feedback predicted subsequent reaction time in the older group.

In conclusion, in older people, arousal systems showed reduced engagement following performance lapses and errors and impaired sensitivity to fluctuations in internal brain state that might be important for attentional regulation.

Significance Statement

Decision confidence is a type of performance evaluation central for appropriate behavioural adjustments. Older people show impairments in the evaluation of their own performance. We investigated, in young and older adults, the link between confidence judgments, pupil-linked arousal responses, and trial-by-trial behavioural adjustments important for optimal task performance. Our findings revealed a distinction between low confidence in response to internally generated lapses and low confidence in response to high sensory noise in young adults and suggested that this ability is impaired in older people at the level of the modulation of the arousal system and the impact on behaviour. This deficit might affect the ability of older people to quickly react to periods of inattention resulting in prolonged attention lapses.