pack mentality. A cast of mind in which individuals cede their will to that of the group, especially under the influence of a strong or charismatic leader. Groupthink.

In animal behavior, “pack mentality” is distinguished from “herd behavior.” In his landmark study, “Geometry for the Selfish Herd,” William Hamilton described herd behavior as the individual seeking to be as close to the center of the group as possible to minimize danger to itself rather than the following of a particular leader. However, in metaphorical usage, these two terms are often used synonymously to describe a tendency to go along with the crowd. In a New York Times article describing the behavior of real estate buyers, broker Barbara Corcoran used the phrase “pack mentality” and defines it this way: “Everybody likes to buy when everybody is buying, and nobody likes to buy when no one is buying.''