This comparison level for alternatives is the standard by which an individual will evaluate the quality of the group in comparison to other groups the individual has the opportunity to join. Thiabaut and Kelley stated that the "comparison level for alternatives can be defined informally as the lowest level of outcomes a member will accept in the light of available alternative opportunities. Joining and leaving groups is ultimately dependent on the comparison level for alternatives, whereas member satisfaction within a group depends on the comparison level.
If membership in the group is above the comparison level for alternatives but below the comparison level, membership will be not be satisfactory; however, the individual will likely join the group since no other desirable options are available. When group membership is below the comparison level for alternatives but above the comparison level, membership is satisfying but an individual will be unlikely to join.
If group membership is below both the comparison and alternative comparison levels, membership will be dissatisfying and the individual will be less likely to join the group. Groups can vary drastically from one another. For example, three best friends who interact every day as well as a collection of people watching a movie in a theater both constitute a group. Past research has identified four basic types of groups which include, but are not limited to: primary groups, social groups, collective groups, and categories. For example, in an experiment,  participants were asked to sort a number of groups into categories based on their own criteria.
Examples of groups to be sorted were a sports team, a family, women, and people at a bus stop.
It was found that participants consistently sorted groups into four categories: intimacy groups, task groups, loose associations, and social categories. These categories are conceptually similar to the four basic types to be discussed. Therefore, it seems that individuals intuitively define aggregations of individuals in this way.
Primary groups are characterized by relatively small, long-lasting groups of individuals who share personally meaningful relationships. Since these groups often interact face-to-face, they know each other very well and are unified. Individuals that are a part of primary groups consider the group to be an important part of their lives.
Consequently, members strongly identify with their group, even without regular meetings.
For example, individuals are born into a primary group, their family, which creates a foundation for them to base their future relationships. Individuals can be born into a primary group; however, primary groups can also form when individuals interact for extended periods of time in meaningful ways. A social group is characterized by a formally organized group of individuals who are not as emotionally involved with each other as those in a primary group.
These groups tend to be larger, with shorter memberships compared to primary groups.
The goals of social groups are often task-oriented as opposed to relationship-oriented. Collectives are characterized by large groups of individuals who display similar actions or outlooks. They are loosely formed, spontaneous, and brief. Categories are characterized by a collection of individuals who are similar in some way. For example, when people treat others differently because of their race, this creates groups of different races. Entitativity is defined by Campbell  as the extent to which collections of individuals are perceived to be a group. The degree of entitativity that a group has is influenced by whether a collection of individuals experience the same fate, display similarities, and are close in proximity.
If individuals believe that a group is high in entitativity, then they are likely to believe that the group has unchanging characteristics that are essential to the group, known as essentialism. The social group is a critical source of information about individual identity.
One's personal identity is defined by more idiosyncratic, individual qualities and attributes. Instead, we make evaluations that are self-enhancing, emphasizing the positive qualities of our own group see ingroup bias.
Our social identity and group membership also satisfies a need to belong. Therefore, one's social identity can have several, qualitatively distinct parts for example, one's ethnic identity, religious identity, and political identity.
Optimal distinctiveness theory suggests that individuals have a desire to be similar to others, but also a desire to differentiate themselves, ultimately seeking some balance of these two desires to obtain optimal distinctiveness. One's collective self may offer a balance between these two desires. In the social sciences, group cohesion refers to the processes that keep members of a social group connected. Group cohesion, as a scientifically studied property of groups, is commonly associated with Kurt Lewin and his student, Leon Festinger.
Lewin defined group cohesion as the willingness of individuals to stick together, and believed that without cohesiveness a group could not exist. Before Lewin and Festinger, there were, of course, descriptions of a very similar group property. For example, Emile Durkheim described two forms of solidarity mechanical and organic , which created a sense of collective conscious and an emotion-based sense of community.
Beliefs within the ingroup are based on how individuals in the group see their other members. Individuals tend to upgrade likeable in-group members and deviate from unlikeable group members, making them a separate outgroup. This is called the black sheep effect. This phenomenon has been later accounted for by subjective group dynamics theory. In more recent studies, Marques and colleagues  have shown that this occurs more strongly with regard to ingroup full members than other members.
Whereas new members of a group must prove themselves to the full members to become accepted, full members have undergone socialization and are already accepted within the group. They have more privilege than newcomers but more responsibility to help the group achieve its goals. Marginal members were once full members but lost membership because they failed to live up to the group's expectations.
They can rejoin the group if they go through re-socialization. Therefore, full members' behavior is paramount to define the ingroup's image. Bogart and Ryan surveyed the development of new members' stereotypes about in-groups and out-groups during socialization. Results showed that the new members judged themselves as consistent with the stereotypes of their in-groups, even when they had recently committed to join those groups or existed as marginal members. They also tended to judge the group as a whole in an increasingly less positive manner after they became full members.
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Nevertheless, depending on the self-esteem of an individual, members of the in-group may experience different private beliefs about the group's activities but will publicly express the opposite—that they actually share these beliefs. One member may not personally agree with something the group does, but to avoid the black sheep effect, they will publicly agree with the group and keep the private beliefs to themselves. If the person is privately self-aware , he or she is more likely to comply with the group even if they possibly have their own beliefs about the situation.
In situations of hazing within fraternities and sororities on college campuses, pledges may encounter this type of situation and may outwardly comply with the tasks they are forced to do regardless of their personal feelings about the Greek institution they are joining. This is done in an effort to avoid becoming an outcast of the group. Full members of a fraternity might treat the incoming new members harshly, causing the pledges to decide if they approve of the situation and if they will voice their disagreeing opinions about it. Individual behaviour is influenced by the presence of others.
These include decisions related to ingroup bias , persuasion see Asch conformity experiments , obedience see Milgram Experiment , and groupthink. There are both positive and negative implications of group influence on individual behaviour. This type of influence is often useful in the context of work settings, team sports, and political activism.
However, the influence of groups on the individual can also generate extremely negative behaviours, evident in Nazi Germany, the My Lai Massacre , and in the Abu Ghraib prison also see Abu Ghraib torture and prisoner abuse. A group's structure is the internal framework that defines members' relations to one another over time. Roles can be defined as a tendency to behave, contribute and interrelate with others in a particular way. Roles may be assigned formally, but more often are defined through the process of role differentiation. A group with a high level of role differentiation would be categorized as having many different roles that are specialized and narrowly defined.
Norms are the informal rules that groups adopt to regulate members' behaviour. Norms refer to what should be done and represent value judgments about appropriate behaviour in social situations. Although they are infrequently written down or even discussed, norms have powerful influence on group behaviour. There are various types of norms, including: prescriptive, proscriptive, descriptive, and injunctive. Intermember Relations are the connections among the members of a group, or the social network within a group.
Group members are linked to one another at varying levels.
Examining the intermember relations of a group can highlight a group's density how many members are linked to one another , or the degree centrality of members number of ties between members. Values are goals or ideas that serve as guiding principles for the group. Values can serve as a rallying point for the team. However, some values such as conformity can also be dysfunction and lead to poor decisions by the team. Communication patterns describe the flow of information within the group and they are typically described as either centralized or decentralized. With a centralized pattern, communications tend to flow from one source to all group members.
Centralized communications allow standardization of information, but may restrict the free flow of information. Decentralized communications make it easy to share information directly between group members. When decentralized, communications tend to flow more freely, but the delivery of information may not be as fast or accurate as with centralized communications.
Another potential downside of decentralized communications is the sheer volume of information that can be generated, particularly with electronic media. Status differentials are the relative differences in status among group members.
When a group is first formed the members may all be on an equal level, but over time certain members may acquire status and authority within the group; this can create what is known as a pecking order within a group. Forsyth suggests that while many daily tasks undertaken by individuals could be performed in isolation, the preference is to perform with other people. In a study of dynamogenic stimulation for the purpose of explaining pacemaking and competition in , Norman Triplett theorized that "the bodily presence of another rider is a stimulus to the racer in arousing the competitive instinct In , Robert Zajonc expanded the study of arousal response originated by Triplett with further research in the area of social facilitation.
In his study, Zajonc considered two experimental paradigms.
In the first—audience effects—Zajonc observed behaviour in the presence of passive spectators, and the second—co-action effects—he examined behaviour in the presence of another individual engaged in the same activity. Zajonc observed two categories of behaviours— dominant responses to tasks that are easier to learn and which dominate other potential responses and nondominant responses to tasks that are less likely to be performed.
In his Theory of Social Facilitation , Zajonc concluded that in the presence of others, when action is required, depending on the task requirement, either social facilitation or social interference will impact the outcome of the task. If social facilitation occurs, the task will have required a dominant response from the individual resulting in better performance in the presence of others, whereas if social interference occurs the task will have elicited a nondominant response from the individual resulting in subpar performance of the task.
Several theories analysing performance gains in groups via drive, motivational, cognitive and personality processes, explain why social facilitation occurs.