Daytime and season do not affect reinforcement learning capacity in a response time adjustment task

Area of Science:

• Cognitive Neuroscience
• Chronobiology

Background:

• Seasonal and circadian rhythms influence physiology, including dopamine neurotransmission, and may play a role in mood disorders.
• Research on the effects of season and time of day on cognitive function, particularly reinforcement learning, is limited.

Purpose of the Study:

• To investigate the impact of seasonal and diurnal variations on adaptive response time optimization in a reward-based learning task.
• To determine if external factors like photoperiodicity and temperature affect reinforcement learning.

Main Methods:

• A reward-based learning task requiring adaptive response time adjustments (fast vs. slow) was administered to 80 German participants.
• Participants were tested twice: once in the morning and once in the evening.
• Testing was conducted during summer and winter to assess seasonal effects.

Main Results:

• No significant effects of daytime, season, photoperiodicity, or temperature were observed on reinforcement learning performance.
• A consistent finding was a slower response speed in the morning compared to the evening across participants.
• These behavioral findings contrast with some existing neurophysiological evidence suggesting potential differences.

Conclusions:

• While this study did not find season or time of day to significantly alter reinforcement learning, a general diurnal effect on response speed was noted.
• The lack of observed behavioral differences may indicate a resilience of this specific cognitive function to seasonal and diurnal changes, or limitations in detecting subtle effects.
• Further research, potentially incorporating neurophysiological measures, is warranted to fully understand the interplay between biological rhythms and cognitive functions like reinforcement learning.