Milieu control is a tactic used within groups to isolate members from society and deepen connections with their associates. It involves the use of controls to shape the environment people interact in, and to dictate the terms of communication within and without the group. A variety of tools can be used for this purpose, including specialized slang and protocols to link group members through a common language and dogma.
This concept was originally developed by Robert Jay Lifton, a psychologist with an interest in cult movements and ingroup identity formation. Lifton's discussion of milieu control focused on the tactics used by cults. He classified it as a form of “thought reform,” a tactic designed to shape the attitudes of members within a cult or similar insular group. Other researchers have since applied it to other settings that meet the criteria but may not necessarily occur in a cult context.
In milieu control, a person in a position of authority uses that power to limit communication and knowledge within a group. Members of the group are discouraged from seeking information available through outside sources, for example. They cannot talk to people outside the group, or are provided with tools they can use to discount or debunk information provided by outsiders. Challenges to the group can create a tighter association with members of the group, as people may feel besieged and justified in believing the ideas developed and promoted within the group.
A common, specialized language is also a part of milieu control. Members of a group may develop their own language, or a particular form of jargon that allows them to distinguish each other and create common ground. As people travel, their buzzwords and slang can identify them, allowing other members of the group to find them. Organizational members and affiliates may also subscribe to a specific dogma and experience social pressure to adhere to it rather than questioning it.
Within the context of the cult research performed by Lifton, milieu control was an important tool for cult leaders. It was one among several things he defined as criteria for thought reform, evidence that a group might be trying to use brainwashing tactics on members to keep them compliant. The presence of milieu control does not necessarily mean an organization is a cult, but could indicate narrow-minded thinking and a lack of interest in information from the outside, which can be a hindrance to some organizations.