The Diurnal Course of Efficiency (Classic Reprint)

Discover how daily rhythms shape thinking and work, and what really influences performance across the day.

This study tracks how mental tasks—from memory to arithmetic—rise and fall with the clock. It presents a broad set of experiments, showing that no single time of day guarantees peak results, and that individual differences matter a lot. The book also highlights the challenges of drawing simple conclusions from varied tests and days, offering a careful look at how researchers measure efficiency in real life.

• Learn how memory, attention, and problem solving vary across morning, noon, and evening.


• See how different tasks respond to time of day and how practice affects results.


• Understand why simple curves can mislead when studying cognitive performance.


• Explore how researchers design multiple-day experiments to capture real-world variation.

Ideal for readers curious about the science of mental energy, work performance, and how timing can affect everyday thinking.