Group: a number of people or things regarded as forming a unity or whole on the grounds of some mutual or common relation or purpose, or classed together because of a degree of similarity. (Oxford) Any number of entities (members) considered as a unit. (NCIt) When a group agrees on most issues, there is a tendency to stifle any dissent. The group anticipates harmony. Can be disastrous because it leads to a failure to listen to or identify all sides of an argument and can result in impulsive decisions. (Kleinman, 49)

Bystander Effect: a phenomenon in which the greater the number of people present, the less likely each individual is to help someone in distress. (Hockenbury, 468) Suggests that people are less likely to provide needed help when they are in groups than when they are alone. Research suggests that the more bystanders that are present at an emergency situation, the less likely it is that any individual will offer help. The greatest likelihood of helping is observed when a single observer witnesses an emergency. (Bamford, 11/30/10)

Coalition: a union, fusion, or combination. (Oxford) Two or more interest groups that join in an effort to advance a shared agenda. (Johnson, 260)

Conformity: the tendency to adjust one’s behavior, attitudes, or beliefs to group norms in response to real or imagined group pressure. (Hockenbury, 454) A form of social influence which results from exposure to the opinions of a majority. (Cardwell, 55) Occurs when people yield to real or imagined social pressure. Within social groups, there is pressure to conform, to look, think and behave like other people in the group. (Bamford, 11/30/10) Also referred to as ‘majority influence.’

Diffusion of Responsibility: both the “bystander effect” and "social loafing" share the phenomenon of a diffusion of responsibility. In a large group, the responsibility for helping or working (contributing to the group) is reduced, because there are more helping and working resources available. Individuals in a group may look around and tell themselves that "someone else will do it." (Bamford, 11/30/10)

Group Behavior: situations where people interact in large or small groups. (Oxford) The procedures through which a group approaches, attacks, and solves a common problem. (MeSH) An attempt to understand and explain how the thoughts, feelings and behavior of individuals, are influenced by the actual, imagined, or implied presence of others. (Cardwell, 236)

Groupthink: the phenomenon where social pressures within the group push its members into a pattern of thought that is characterized by self-deception, forced manufacture of consent, and conformity to group values and ethics. (Fisher, 93) The tendency for certain types of groups to reach decisions that are extreme and which tend to be unwise or unrealistic. (Cardwell, 116) Occurs when members of a cohesive group emphasize consensus at the expense of critical thinking in arriving at a decision. When a group is discussing a problem, and the group seems to reach consensus, it becomes very difficult for an individual to oppose the group and think critically about alternatives and possible options. Groupthink occurs frequently in jury situations, where the majority of the jury is in agreement about the verdict, but a minority of jurors want to see more evidence or think about the case more. In those cases, the minority jurors are likely to succumb to groupthink, and fail to present conflicting opinions to the rest of the group. (Bamford, 11/30/10) Examples of groupthink go wrong include mass riots and lynch mobs. To combat groupthink, authentic dissent should be nurtured. (Kleinman, 49) Editor's note - term coined by Yale psychologist Irving Janis in 1972.

Ingroup: any group of which we perceive ourselves to be a member. (Cardwell, 130) Groups of people with which one identifies. (Floyd, G3) People you consider fundamentally similar to yourself because of their interests, affiliations, or backgrounds. (McCornack, 87)

Outgroup: groups of people with which one does not identify. (Floyd, G5) People you consider fundamentally different from you because of their interests, affiliations, or backgrounds. (McCornack, 87)

Social Loafing: a reduction in effort by individuals when they work in groups as compared to when they work by themselves. In group situations, less effort is produced by each individual than when that individual is working alone. These problems are sometimes observed in group projects, wherein each member of the group produces less effort working toward the group goal than if the individual was working alone. (Bamford, 11/30/10)