In the 1920s and 1930s, researchers at the Hawthorne Works (a Western Electric factory near Chicago) studied how physical working conditions affected worker productivity. What they found instead became one of the most discussed phenomena in management psychology.

The Finding

Worker productivity improved whenever conditions were changed — whether lighting was increased or decreased, whether break times were added or removed. The changes themselves seemed less important than the fact of being studied.

The Hawthorne Effect

People modify their behavior when they know they are being observed. The act of observation itself changes the thing being observed.

Implications

• Research design: Control groups and blinding exist specifically to counteract Hawthorne effects
• Management: Attention and interest from managers can boost performance — independent of the specific intervention
• Performance reviews: The process of being evaluated increases performance, separate from the content of the review

Historical Note

The original Hawthorne studies have been significantly reanalyzed and the effect is more nuanced than the original interpretation. But the core insight — that observation changes behavior — is robust.

Reference:

Wikipedia: Hawthorne Effect

https://en.wikipedia.org/wiki/Hawthorne_effect