Effects of personality and loss of anonymity on aggression: a reevaluation of deindividuation.

Zimbardo's deindividuation hypothesis was reexamined by individuating some subjects. Twelve four-person groups administered shock to a confederate in a 2 x 2 x 2 factorial design with two levels of social individuation (subjects' level of anonymity to group members), two levels of nonsocial individuation (subjects' opportunity to give identifying information to the experimenter on a word association test) and two levels of individual differences. It was found that subjects, who individuated themselves by giving information to the experimenter on the word association test showed more, not less, antisocial behavior. Furthermore, this increased antisocial behavior was exhibited only by externally oriented subjects: those with an external locus of control and a low mysticism score. Some of those more antisocial subjects were also more likely to report feeling like they stood out from the group. It was concluded that antisocial behavior in this paradigm may thus be a response to experimenter demand felt most strongly when subjects felt most identifiable.     

Effects of personality and loss of anonymity on aggression: A revaluation of deindividuation1

Zimbardo's deindividuation hypothesis was reexamined by individuating some subjects. Twelve four-person groups administered shock to a confederate in a 2 × 2 × 2 factorial design with two levels of social individuation (subjects' level of anonymity to group members), two levels of nonsocial individuation (subjects' opportunity to give identifying information to the experimenter on a word association test), and two levels of individual differences. It was found that subjects who individuated themselves by giving information to the experimenter on the word association test showed more, not less, antisocial behavior. Furthermore, this increased antisocial behavior was exhibited only by externally oriented subjects: those with an external locus of control and a low mysticism score. Some of those more antisocial subjects were also more likely to report feeling like they stood out from the group. It was concluded that antisocial behavior in this paradigm may thus be a response to experimenter demand felt most strongly when subjects felt most identifiable.     

Anger arousal,deindividuation, and aggression

We tested the notion that angered persons' aggression would be increased through a process of excitation transfer when they are deindividuated, but that individuated subjects would be most aggressive in circumstances under which they could use the information that they had ingested an arousing drug as a pretext for their aggression. Sixty-two male undergraduates participated under either deindividuated or individuated conditions, ingested either 350 mg of caffeine or a placebo, were informed that they had either taken a stimulant or a nonarousing drug, and were all angered by a confederate. According to prediction, when deindividuated and aroused by caffeine the amount of noxious stimulation subjects delivered to the provocateur was greater if they believed that the drug they had taken was nonarousing than if they thought it was a stimulant; in contrast, individuated subjects' aggression was greater when aroused subjects believed the drug was a stimulant. The results are discussed in terms of excitation transfer and the effect of aggression inhibition on the use of information about one's arousal.     

Effects of anonymity on antisocial behavior committed by individuals

The present study examined association between anonymity and antisocial individual behavior without any influence from the presence of others. Anonymity was operationally defined as consisting of two components, nonidentifiability and nonaccountability. Antisocial behavior was defined as rule-breaking behavior seeking a monetary reward. It was hypothesized that anonymity would increase antisocial behavior among individuals. Undergraduate students (20 men, 50 women) were recruited from two psychology classes and were randomly assigned to four experimental conditions (Anonymous, Nonidentifiable, Nonaccountable, and Nonanonymous) to examine whether they would violate game rules to obtain the monetary reward through anonymity. Only participants in the Anonymous condition violated the rules to obtain the reward. Implications for the effects of anonymity on antisocial individual behavior are discussed.     

Effects of female presence on intrasexual aggression in male lizards,Podarcis hispanicus

Resource value and expected gain in reproduction may affect motivation to fight and the likelihood of winning. Previous experiments have showed that males increase their fighting effort when defending a territory that contains females. However, we hypothesized that for an intruding lizard, the value of a new territory may be lower if he already has a female in his own territory, and consequently, aggressivity should be lesser than if he has no access to any female. We staged encounters between males of the lizard Podarcis hispanicus in outdoor terraria to analyze the outcome and detailed behaviors involved in agonistic interactions in the presence or absence of a female in the terraria of resident and intruders. Our results showed that when a female was present, the level of aggressivity of the resident male was higher; the probability of winning the contest also increased, but only if the intruding male had no females in his own terraria. In contrast, when the intruding male was also the owner of another territory containing a female, residents were less aggressive. We suggest that the lack of information on the reproductive state of an unfamiliar female may be enough to decrease fighting motivation of an intruding male, if he has more expectations of success with his own familiar female. We conclude that differences in expected reproductive success with different females may help to decide the outcome of conflicts between males quicker and cheaper. Aggr. Behav. 28:491–498, 2002. © 2002 Wiley‐Liss, Inc.     

Visibility and anonymity effects on attraction and group cohesiveness

This study investigated attraction and group cohesiveness under different visibility and anonymity conditions for social categories that differed in their capacity to be visually cued. Using computer‐mediated communication in 36 mixed gender (visually cued category) and nationality (non‐visually cued category) groups, we manipulated social category salience (via discussion topic), and anonymity versus visibility (via live video links). Under high salience, the effects of anonymity versus visibility were moderated by availability of visible category cues. Visibility increased attraction and cohesiveness for visually cued groups, whereas anonymity increased attraction and cohesiveness for non‐visually cued groups. Path analysis showed that, under high salience, effects of visibility and anonymity were mediated by self‐categorization processes, triggered by prototypicality of self in the case of non‐visually cued groups under anonymity. In low salience conditions, visibility directly cued attraction independently from self‐categorization, in line with relational attraction processes. Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of temperature and prior residence on territorial aggression in the convict cichlid Cichlasoma nigrofasciatum

Aggression in the convict cichlid Cichlasoma nigrofasciatum was measured under two different environmental parameters after introduction of a conspecific intruder. Measurements were made after 24-hr and 48-hr teritorial residence times at both 26°C and 30°C. Eight fish established territories in individual tanks each containing one terra cotta pot. Intruders contained in a glass cylinder were introduced into the territories. An opaque divider separating the resident from the intruder was removed after a 15-min acclimation period. At 26°C, we observed a significant difference in the mean number of bites of the cichlids of 24-hr and 48-hr residency durations, whereas, at 30°C, such a difference did not exist. Statistical analysis showed that cichlids exhibited more aggression at 30°C than at 26°C. Increased aggression levels at the higher temperature may be related to the fact that cichlids establish territories and spawn at about 30°C.     

Behavioral economic influences on treatments designed to decrease destructive behavior.

In behavioral economics terms, response allocation is viewed as an exchange between the price of and the demand for reinforcers associated with various responses. In this study, behavioral economics principles were used to develop and evaluate a treatment package that reduced destructive behavior to zero while communication and compliance were increased.     

Effects of movie violence on aggression in a field setting as a function of group dominance and cohesion.

In this quasi-experimental field study, delinquent members belonging to two cottages viewed aggressive commercial movies every evening for a week, while at the same time, subjects from two other cottages were exposed to neutral commercial movies. Behavioral observations were obtained through a nonhier-archical, minimally inferential procedure of a time-sampling nature; they were taken during a baseline week (at noon and in the evening), a treatment week (noon and evening) and a posttreatment week (noon). The main immediate effects of the violent films were an overall increase of both active behaviors and physical aggression; the effects on verbal aggression were more persistent but limited to one of the two cottages. On the other hand, more interactions occurred as an immediate consequence of viewing the films in both neutral treatment cottages; moreover, one of these two cottages also decreased its level of physical (short-term effect) and verbal (short- and long-term effects) aggression. In the aggressive treatment cottage, which was most affected, subjects who were most dominant, most popular, and least popular were influenced the most: an opposite effect was exhibited by those subjects who were judged as least aggressive by their peers. Complementary data are presented and discussed; the difference between the single individual laboratory paradigm and the existing group field paradigm is especially stressed.