Behavioral contagion

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Behavioral contagion is a type of social influence. It refers to the propensity for certain behavior exhibited by one person to be copied by others who are either in the vicinity of the original actor, or who have been exposed to media coverage describing the behavior of the original actor. It was originally used by Gustave Le Bon (1895) to explain undesirable aspects of behavior of people in crowds[1]. A variety of behavioral contagion mechanisms were incorporated in models of collective human behavior[2][3][4].

The occurrence of behavioral contagion has been attributed to a variety of different factors, but the predominant theory is that of the reduction of restraints, put forth by Fritz Redl in 1949 and analyzed in depth by Ladd Wheeler in 1966.[5] Even with the popularity of this theory, social psychologists acknowledge a number of factors that influence the likelihood of behavioral contagion occurring, such as deindividuation (Festinger, Pepitone, & Newcomb, 1952) and the emergence of social norms (Turner, 1964).[6] Freedman, Birsky and Cavoukian (1980) have also focused on the effects of physical factors on contagion, in particular, density and number.[6]

Ogunlade (1979, p. 205) describes behavioral contagion as a “spontaneous, unsolicited and uncritical imitation of another’s behavior” that occurs when certain variables are met: a) the observer and the model share a similar situation or mood (this is one way behavioral contagion can be readily applied to mob psychology); b) the model’s behavior encourages the observer to review his condition and to change it; c) the model’s behavior would assist the observer to resolve a conflict by reducing restraints, if copied; and d) the model is assumed to be a positive reference individual.[7]

Factors influencing contagion[edit]

Reduction of restraints[edit]

Behavioral contagion is a result of the reduction of fear or restraints – aspects of a group or situation which prevent certain behaviors from being performed.[5] Restraints are typically group-derived, meaning that the “observer”, the individual wishing to perform a certain behavior, is constrained by the fear of rejection by the group, who would view this behavior as a “lack of impulse control”.[5]

An individual (the “observer”) wants to perform some behavior, but that behavior would violate the unspoken and accepted rules of the group or situation they are in; these rules are the restraints preventing the observer from performing that action. Once the restraints are broken or reduced the observer is then “free” to perform the behavior his- or herself; this is achieved by the “intervention” of the model. The model is another individual, in the same group or situation as the observer, who performs the behavior which the observer wished to perform.[5] Stephenson and Fielding (1971) describe this effect as “[Once] one member of a gathering has performed a commonly desired action, the payoffs for similar action or nonaction are materially altered. … [The] initiator, by his action, establishes an inequitable advantage over the other members of the gathering which they may proceed to nullify by following his example. ”[1]

Density and number[edit]

Density refers to the amount of space available to a person – high density meaning there is less space per person – and number refers to the size of the group.[6] Freedman (1975) put forth the intensification theory, which posits that high density makes the other people in a group more salient features of the environment, this magnifying the individual’s reaction to them. Research has shown that high density does in fact increase the likelihood of contagion (Freedman, 1975; Freedman, Birsky, & Cavoukian, 1980).[6] Number also has an effect on contagion, but to a lesser degree than density.[6]

Identity of the model[edit]

Stephenson and Fielding (1971) state that the identity of the model is a factor that influences contagion (p. 81).[1] Depending on the behavior, sex of the model may be a factor in the contagion of that behavior being performed by other individuals – particularly in instances of adult models performing aggressive behavior in the presence of children-observers (Bandura, Ross, & Ross, 1963) {Imitation of film-mediated aggressive models}.[5] In this particular series of experiments – Albert Bandura’s Bobo doll experiments from 1961 and 1963 – where the behavior of children was studied after the children watched an adult model punching a bobo doll and the model received a reward, a punishment, or there were no consequences, the analyses revealed that the male model influenced the participants’ behavior to a greater extent than did the female model; this was true for both the aggressive and the nonaggressive male models (p. 581).[8]

Personality of the observer[edit]

Ogunlade (1979) found that extroverts, who are described as impulsive and sociable individuals, are more likely to be susceptible to contagion than introverted individuals, who are described as reserved and emotionally controlled.[7]

Social norms[edit]

Gino, Ayal and Ariely (2009) state that an important factor influencing contagion is the degree to which the observer identifies with the others of the group (p. 394).[9] When identification with the rest of the group is strong, the behaviors of the others will have a larger influence.[9]

Similarities and differences with other types of social influence[edit]

Contagion is only one of a myriad of types of social influence.

Conformity / social pressures[edit]

Conformity is a type of social influence that is very similar to contagion.[5] It is almost identical to another type of social influence, "pressures toward uniformity" (social pressures) (Festinger, 1954), which differ only in the research techniques they are associated with (Wheeler, 1966, p. 182).[5]

Both conformity and contagion involve some sort of conflict, but differ in the roles other individuals play in that conflict.[5] In conformity, the other individuals of the group try to pressure the observer into performing a behavior; the model then performs some other behavior in the vicinity of the observer. This results in the observer creating restraints against the pressured behavior and a conflict between the pressured behavior and the behavior performed by the model. In the end, the observer either performs the model’s behavior his-/herself, rejects the model, or pressures the model to perform the original pressured behavior (Wheeler, Table 1).[5] In contagion, the model’s behavior results in the removing of restraints and the resolving of the conflict, while in conformity, the model’s behavior results in the creation of restraints and of the conflict.[5]

Social facilitation[edit]

Social facilitation, another type of social influence, is distinguished from contagion, as well as from conformity and social pressures, by the lack of any marked conflict.[5] It is said to occur when the performance of an instinctive pattern of behavior by an individual acts as a releaser for the same behavior in others, and so initiates the same line of action in the whole group (Thorpe, 1956, p. 120).[5] Bandura and Walters (1963, p. 79), give the example of an adult, who has lost the unique aspects of the dialect of the region where they were raised, returns for a visit and “regains” those previously lost patterns of speech.[5] Starch (1911) referred to this phenomenon as an “unintentional or unconscious imitation”.[5]


Imitation is different from contagion in that it is learned via reward and punishment and is generalized across situations.[5] Imitation can also be a generic term for contagion, conformity, social pressures, and social facilitation.[5]

(Wheeler, 1966, Table 1)[5] Dynamics of selected influence processes
Stages in influence process Behavioral contagion Social pressures and conformity Social facilitation
Observer’s initial conditions Instigated to BN*. Internal restraints against BN. Instigated to BP*. No restraints. No restraints against BN or BP. No instigation to BN or BP.
Model’s behavior Model performs BN. Model performs BN. Model performs BN.
Hypothetical processes Reduction of model’s restraints against BN. Fear reduction. Creation of restraints against BP. Conflict between BN and BP. Cognitive-behavioral chaining, CS* elicits CR*, inertia overcome.
Observer’s behavior Observer performs BN. Observer performs BN (or rejects model or induces model to perform BP). Observer performs BN.
  • BN = initial behavior
  • BP = pressured behavior
  • CS = conditioned stimulus
  • CR = conditioned response

Competition contagion on non-competitors[edit]

While behavioral contagion is largely about how people might be affected by observations of the expressions or behavior of others, research has also found contagion in the context of a competition where mere awareness of an ongoing competition can have an influence on noncompetitors’ task performance, without any information about the actual behavior of the competitors. [10].


Effects of group pressure[edit]

Behavioral contagion, largely discussed in the behaviors of crowds, and closely related to emotional contagion, plays a large role in gatherings of two or more people.[1] In the original Milgram experiment on obedience, for example, where participants, who were in a room with only the experimenter, were ordered to administer increasingly more severe electrical shocks as punishment to a person in another room (from here on out, referred to as the “victim”), the conflict or social restraint experienced by the participants was the obligation to not disobey the experimenter – even when shocking the victim to the highest shock level given, a behavior which the participants saw as opposing their personal and social ideals (Milgram, 1965, p. 129).[11]

Milgram also conducted two other experiments, replications of his original obedience experiment, with the intent being to analyze the effect of group behavior on participants: instead of the subject being alone with the experimenter, two confederates were utilized. In the first of the two experiments, “Groups for Disobedience,” the confederates defied the experimenter and refused to punish the victim (p. 130).[11] This produced a significant effect on the obedience of the participants: in the original experiment, 26 of the 40 participants administered the maximum shock; in the disobedient groups experiment, only 4 of 40 participants administered the highest level of voltage (Table 1).[11] Despite this high correlation between shock level administered and the obedience of the group in the disobedient groups experiment, there was no significant correlation for the second of the replicated experiments: “Obedient Groups”, where the confederates did not disobey the experimenter and, when the participant voiced angst regarding the experiment and wished to stop administering volts to the victim, the confederates voiced their disapproval (p. 133).[11] Milgram concludes the study by remarking that “the insertion of group pressure in a direction opposite that of the experimenter’s commands produces a powerful shift toward the group. Changing the group movement does not yield a comparable shift in the [participant’s] performance. The group success in one case and failure in another can be traced directly to the configuration of motive and social forces operative in the starting situation.” That is, if the group’s attitudes are similar to or compatible with the participant’s/observer’s, there is a greater likelihood that the participant/observer will join with the group (p. 134).[11]

See also[edit]


  1. ^ a b c d Stephenson, G. M., & Fielding, G. T. (1971). An experimental study of the contagion of leaving behavior in small gatherings. Journal of Social Psychology, 84(1), 81-91.
  2. ^ Castellano C, Fortunato S, and Loreto V (2009) Statistical physics of social dynamics. Rev Mod Phys 81(2): 591–646.
  3. ^ Braha D (2012) Global Civil Unrest: Contagion, Self-Organization, and Prediction. PLoS ONE 7(10): e48596.
  4. ^ Braha, D., & de Aguiar, M. A. (2017). Voting contagion: Modeling and analysis of a century of U.S. presidential elections. PLoS ONE 12(5): e0177970.
  5. ^ a b c d e f g h i j k l m n o p q Wheeler, L. (1966). Toward a theory of behavioral contagion. Psychological Review, 73(2), 179-192. doi:10.1037/h0023023
  6. ^ a b c d e Freedman, J. L., Birsky, J., & Cavoukian, A. (1980). Environmental determinants of behavioral contagion: density and number. Basic and Applied Social Psychology, 1(2), 155-161.
  7. ^ a b Ogunlade, J. O. (1979). Personality characteristics related to susceptibility to behavioral contagion. Social Behavior and Personality: an International Journal, 7(2), 205.
  8. ^ Bandura, A., Ross, D., & Ross, S. A. (1961). Transmission of aggression through imitation of aggressive models. Journal of Abnormal and Social Psychology, 63(3), 575-582.
  9. ^ a b Gino, F., Ayal, S., & Ariely, D. (2009). Contagion and differentiation in unethical behavior: the effect of one bad apple on the barrel. Psychological Science, 20(3), 393-398. doi:10.1111/j.1467-9280.2009.02306.x
  10. ^ Kc, R. P., M. Kunter, and V. Mak. "The influence of a competition on noncompetitors." Proceedings of the National Academy of Sciences of the United States of America (2018).
  11. ^ a b c d e Milgram, S. (1965). Liberating effects of group pressure. Journal of Personality and Social Psychology, 1(2), 127-134.

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