Author's School

Graduate School of Arts & Sciences

Author's Department/Program



English (en)

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Todd S Braver


It is becoming increasingly appreciated that affective influences can contribute strongly to goal-oriented cognition and behaviour. However, much work is still needed to properly characterize these influences and the mechanisms by which they contribute to cognitive processing. An important question concerns the nature of emotional manipulations: i.e., direct induction of affectively valenced subjective experience) versus motivational manipulations: e.g., delivery of performance-contingent rewards and punishments) and their impact on cognitive control. Given previous empirical evidence suggesting that positive emotion may enhance cognitive flexibility and reactive control, while performance-contingent rewards may enhance goal maintenance and proactive control, we sought to directly compare the effects of positive emotion and reward manipulations on cognitive control in a single group of subjects, using the AX-Continuous Performance Task: AX-CPT) paradigm, which allows measurement of the relative balance between proactive and reactive cognitive control. Pupil dilation during task performance was measured using high-resolution pupillometry as a secondary, high temporal-resolution measure of cognitive dynamics, and individual difference measures: both personality and cognition-related) were collected to examine whether the effects of emotional and motivational manipulations on cognition were mediated by such measures. We observed expected increases in proactive control and pupil dilation under reward incentive, at both sustained: block-based) and transient: trial-based) timescales. Effects under positive emotion were more complex: while performance and pupil activity were also suggestive of a mild shift towards proactive control, this effect was much weaker than under reward incentive. Surprisingly, reward-related individual differences did not predict changes in cognitive performance or pupil dilation under incentive. These findings provide evidence that positive emotion and reward may be dissociable constructs. Further, they replicate previous findings that reward may enhance goal representation and proactive control, but attest to the complexity and heterogeneity of possible positive emotion effects. Experimental limitations and future directions are discussed as possible strategies to address these findings and extend their observations, towards the goal of building a more comprehensive science of affect-cognition interactions.


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