Two or more people who share a common definition and evaluation of themselves and behave in accordance with such a definition.

Dynamic relationship between the group and its members that describes the passage of members through a group in terms of commitment and of changing roles.

Division of a group into different roles that often differ with respect to status and prestige.

The property of a group that affectively binds people, as group members, to one another and to the group as a whole, giving the group a sense of solidarity and oneness.

Attitudinal and behavioural uniformities that define group membership and differentiate between groups.

An improvement in the performance of well-learned/ easy tasks and a deterioration in the performance of poorly learned/ difficult tasks in the mere presence of members of the same species.

Arousal that motivates performance of habitual behaviour patterns.

Drive because people have learned to be apprehensive about being evaluated.

Drive because people are distracting and produce conflict between attending to the task and to the audience.

A reduction in individual effort when working on a collective task (one in which our outputs are pooled with those of other group members) compared with working either alone or co-actively (our outputs are not pooled).

Gaining the benefits of group membership by avoiding costly obligations of membership and by allowing other members to incur those costs.

Increase effort on a collective task to compensate for other group members’ actual, perceived or anticipated lack of effort or ability.

Getting group members to achieve the group’s goals.

Leaders who use a style based on giving orders to followers.

Leaders who use a style based on consultation and obtaining agreement and consent from followers.

Leaders who use a style based on disinterest in followers.

Explicit or implicit decision-making rules that relate individual opinions to a final group decision.

Uninhabited generation of as many ideas as possible in a group, in order to enhance group creativity.

A mode of thinking in highly cohesive group in which the desire to reach unanimous agreement overrides the motivation to adopt proper rational decision-making procedures.

Tendency for group discussion to produce more extreme group decisions than the mean of members’ pre-discussion opinions, in the direction favoured by the mean.

All group members need to agree on decisions.

Majority percentage of group agrees on a consensus.

Discussion about solution that can be demonstrated to be correct.

The group ultimately adopts a decision in line with the direction of the first idea in opinion shown by any member of the group.