The Hawthorne effect (also referred to as the observer effect) is a type of reactivity in which individuals modify or improve an aspect of their behavior in response to their awareness of being observed. The original “Hawthorne effect” study at the Hawthorne Works suggested that the novelty of being research subjects and the increased attention from such could lead to temporary increases in workers’ productivity. (Wikipedia)

In case of epidemiological studies, this effect can produce a subject bias, if the subject know that they are being a part of a study.

Potential MCQ:

Hawthorne Effect is related to
a. Neynam bias
b. selection bias
c. subject bias
d. measurement bias