herd instinct

WordReference Random House Unabridged Dictionary of American English © 2025

herd′ in′stinct, 

1. Animal Behavior the impulse or tendency toward clustering or acting in a group, esp. the presumed instinct toward or need for gregariousness and conformity.

• 1905–10

Collins Concise English Dictionary © HarperCollins Publishers::

herd instinct noun

1. the inborn tendency to associate with others and follow the group's behaviour