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ABSTRACT
A range of evidence suggests that human reward functioning is partly driven by the endogenous circadian system, generating 24-hour rhythms in behavioural measures of reward activation. Reward functioning is multifaceted but literature to date is largely limited to measures of self-reported positive mood states. The aim of this study was to advance the field by testing for hypothesised diurnal variation in previously unexplored components of psychological reward: ‘wanting’, liking, and learning using subjective and behavioural measures. Risky decision making (automatic Balloon Analogue Risk Task), affective responsivity to positive images (International Affective Pictures System), uncued self-reported discrete emotions, and learning-contingent reward (Iowa Gambling Task) were measured at 10.00 hours, 14.00 hours, and 19.00 hours in a counterbalanced repeated measures design with 50 healthy male participants (aged 18–30). As hypothesised, risky decision making (unconscious ‘wanting’) and ratings of arousal towards positive images (conscious wanting) exhibited a diurnal waveform with indices highest at 14.00 hours. No diurnal rhythm was observed for liking (pleasure ratings to positive images, discrete uncued positive emotions) or in a learning-contingent reward task. Findings reaffirm that diurnal variation in human reward functioning is most pronounced in the motivational ‘wanting’ components of reward.
Declaration of interest
The authors have no commercial associations that might pose a conflict of interest in connection with this manuscript.
Funding
The authors received financial support for this study from the Barbara Dicker Brain Sciences Foundation.
Notes
1 IAPS image numbers: 1440, 1630, 1710, 1722, 2340, 2530, 4085, 4142, 4310, 4311, 4659, 4668, 4676, 4697, 5199, 5825, 5829, 8158, 8190, 8496