Research on bystander intervention has produced a great number of studies showing that the presence of other people in a critical situation reduces the likelihood that an individual will help. As the last systematic review of bystander research was published in 1981 and was not a quantitative meta-analysis in the modern sense, the present meta-analysis updates the knowledge about the bystander effect and its potential moderators. The present work (a) integrates the bystander literature from the 1960s to 2010, (b) provides statistical tests of potential moderators, and (c) presents new theoretical and empirical perspectives on the novel finding of non-negative bystander effects in certain dangerous emergencies as well as situations where bystanders are a source of physical support for the potentially intervening individual. In a fixed effects model, data from over 7,700 participants and 105 independent effect sizes revealed an overall effect size of g = -0.35. The bystander effect was attenuated when situations were perceived as dangerous (compared with non-dangerous), perpetrators were present (compared with non-present), and the costs of intervention were physical (compared with non-physical). This pattern of findings is consistent with the arousal-cost-reward model, which proposes that dangerous emergencies are recognized faster and more clearly as real emergencies, thereby inducing higher levels of arousal and hence more helping. We also identified situations where bystanders provide welcome physical support for the potentially intervening individual and thus reduce the bystander effect, such as when the bystanders were exclusively male, when they were naive rather than passive confederates or only virtually present persons, and when the bystanders were not strangers.

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In many nonhuman species of vertebrates, females are attracted to red on male conspecifics. Red is also a signal of male status in many nonhuman vertebrate species, and females show a mating preference for high-status males. These red-attraction and red-status links have been found even when red is displayed on males artificially. In the present research, we document parallels between human and nonhuman females' response to male red. Specifically, in a series of 7 experiments we demonstrate that women perceive men to be more attractive and sexually desirable when seen on a red background and in red clothing, and we additionally show that status perceptions are responsible for this red effect. The influence of red appears to be specific to women's romantic attraction to men: Red did not influence men's perceptions of other men, nor did it influence women's perceptions of men's overall likability, agreeableness, or extraversion. Participants showed no awareness that the research focused on the influence of color. These findings indicate that color not only has aesthetic value but can carry meaning and impact psychological functioning in subtle, important, and provocative ways.

Previous research has documented that playing violent video games has various negative effects on social behavior in that it causes an increase in aggressive behavior and a decrease in prosocial behavior. In contrast, there has been much less evidence on the effects of prosocial video games. In the present research, 4 experiments examined the hypothesis that playing a prosocial (relative to a neutral) video game increases helping behavior. In fact, participants who had played a prosocial video game were more likely to help after a mishap, were more willing (and devoted more time) to assist in further experiments, and intervened more often in a harassment situation. Results further showed that exposure to prosocial video games activated the accessibility of prosocial thoughts, which in turn promoted prosocial behavior. Thus, depending on the content of the video game, playing video games not only has negative effects on social behavior but has positive effects as well.

Common explanations for the failure of groups to solve so-called hidden profiles focus on group processes, namely insufficient discussion of unshared information and premature consensus on a suboptimal alternative. As 2 experiments show, even in the absence of such group processes, hidden profiles are hardly ever solved. In Experiment 1, participants first received individual information about a personnel selection task and then read a group discussion protocol containing full information exchange. If the individual information was misleading (hidden profile), most participants failed to detect the correct alternative. In Experiment 2, it was determined that this effect is due to preference-consistent evaluation of information that constitutes an individual-level process mediating the failure of group members to solve hidden profiles.

"Previous research has shown that exposure to violent media increased aggression-related affect and thoughts, physiological arousal, and aggressive behavior as well as decreased prosocial tendencies. The present research examined the hypothesis that exposure to prosocial media promotes prosocial outcomes. Three studies revealed that listening to songs with prosocial (relative to neutral) lyrics increased the accessibility of prosocial thoughts, led to more interpersonal empathy, and fostered helping behavior. These results provide first evidence for the predictive validity of the General Learning Model [Buckley, K. E., & Anderson, C. A. (2006). A theoretical model of the effects and consequences of playing video games. In P. Vorderer, & J. Bryant, (Eds.), Playing video games: Motives responses and consequences (pp. 363–378). Mahwah, NJ: Lawrence Erlbaum Associates] for the effects of media with prosocial content on prosocial thought, feeling, and behavior." [author's abstract

Previous research in bystander intervention found that the presence of other bystanders reduces helping behaviour in an emergency (bystander effect). This research was mainly conducted in the context of non-dangerous, non-violent emergencies. We hypothesize that the classic bystander effect does not occur in more dangerous situations because: a) they are faster and more clearly recognized as emergency situations; and b) higher costs for refusing help increase the accepted costs for helping. Following this line of reasoning, the present research tests whether the bystander effect is affected by the degree of the emergency's potential danger. Results supported our expectations: In situations with low potential danger, more help was given in the solitary condition than in the bystander condition. However, in situations with high potential danger, participants confronted with an emergency alone or in the presence of another bystander were similarly likely to help the victim.

Previous research has shown that exposure to prosocial songs increased the accessibility of prosocial thoughts, led to more interpersonal empathy, and fostered helping behavior. However, inasmuch as cognition, affect, and behavior were measured in different studies, it remained unclear what variable constituted the mediating path from media exposure to action. This was tested in the present research. In four studies, listening to songs with prosocial, relative to neutral, lyrics increased helping behavior. This effect was mediated by interpersonal empathy. The results are consistent with the general learning model and point to the importance of the affective route in explaining how media exposure influences social behavior.