Circadian Disruption from Afternoon Caffeine Implicates Impaired Predictive Coding in High School Juniors
Sarah Chambers
11/08/2026
Predictive coding refers to the hierarchical neuronal process in which the brain generates expectations about incoming sensory information and minimizes prediction error. This system is critically dependent on sleep quality-particularly REM (rapid eye movement). REM supports synaptic downscaling, hippocampal replay, and prefrontal-hippocampal plasticity. Although juniors in high school frequently consume caffeine late in the day, the potential impact of caffeine timing on predictive coding related functioning has not been extensively examined.
This study investigated whether caffeine intake after 3pm is associated with reduced predictive coding abilities in high school juniors. Forty juniors from a variety of North Carolina high schools completed an extensive survey assessing sleep timing, caffeine consumption, and everyday cognitive behaviors. These behaviors related to prediction, error detection, and mental sharpness, allowing us to assess predictive coding ability and cognitive processes.
Students who consumed caffeine after 3 pm reported a similar sleep duration to other juniors who avoided consuming caffeine in the late afternoon. Surprisingly, they went to bed significantly later and exhibited lower predictive coding scores. This suggests that caffeine may disrupt REM-dependant neural processes, even though total sleep time appears adequate. REM sleep supports synaptic homeostasis, hippocampal ripple-spindle coupling, and the updating of internal generative models. Because of this, reductions in REM quality may impair the brain’s ability to efficiently process errors in prediction.
These results align with prior juvenile sleep research. These findings show that afternoon caffeine delays sleep onset, reduces REM sleep, and impairs attention and error monitoring. They also highlight the importance of caffeine timing in shaping cognitive efficiency during a period of increased academic demand, a common experience during junior year. Understanding how everyday habits such as late‑day caffeine use influence prediction, attention, and cognitive stability (predictive coding) can potentially help students make positive choices that better support learning, performance, and well-being.