February 23, 2026
Overview:
Our ability to concentrate and think clearly shifts over the course of the day. This is driven by the body’s internal clock, the circadian rhythm, which regulates sleep and alertness. During adolescence, this internal clock naturally shifts, which is why many teenagers feel more alert in the afternoon or evening.
Previous research has explored whether the timing of exams influences performance. However, most studies have relied on high-stakes testing environments where students knew their exam schedules in advance, and assessments were limited to standard school hours. When test times are predictable, students may adjust their sleep, study patterns, or effort, making it difficult to determine whether differences in scores are truly due to time of day.
This One Health Trust collaborative article explores what happens when test timing varies unexpectedly, allowing for a clearer understanding of how time of day itself affects performance.
The Question:
Does the time of day directly affect how well children, adolescents, and young adults perform on cognitive tests?
The Findings:
The researchers examined seven years of testing data from children, adolescents, and young adults in India. Assessments were administered at varying times between 8 a.m. and 10 p.m., and participants were not informed of their test timing far in advance.
The results showed consistent time-of-day effects. Performance declined around lunchtime compared to early morning testing. In contrast, evening testing was associated with higher scores across multiple subjects, including native language, English, mathematics, and reasoning assessments. The largest improvements were observed among adolescents and young adults, suggesting that older students performed better later in the day.
These findings indicate that timing plays an important role in cognitive performance. Educational institutions may wish to consider how test schedules align with students’ biological rhythms. Similarly, employers may benefit from assigning cognitively demanding tasks at times when young workers are likely to be more alert.
The study was conducted in rural, low-income settings, and the findings may not be generalizable for all contexts, but the results provide robust evidence that time of day itself can influence cognitive performance.
Read the article published in SSRN here.
