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The Bystander-Effect: A Meta-Analytic Review on Bystander Intervention
in Dangerous and Non-Dangerous Emergencies
Peter Fischer
University of Regensburg Joachim I. Krueger
Brown University
Tobias Greitemeyer
University of Innsbruck Claudia Vogrincic
University of Graz
Andreas Kastenmu¨ller
Liverpool John Moores University Dieter Frey
University of Munich
Moritz Heene, Magdalena Wicher, and Martina Kainbacher
University of Graz
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), perpe-
trators 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.
Keywords: bystander effect, bystander intervention, dangerous emergencies, helping, meta-analysis
On the 12th September, 2009, Dominik Brunner was murdered at a
German train station after he helped little children against two per-
petrators. He has not chosen to look the other way, but sacrificed
himself when others were in need. —Dominik Brunner Foundation
It is a denial of justice not to stretch out a helping hand to the fallen;
that is the common right of humanity. —Seneca (5 BC–65 AD)
The bystander effect refers to the phenomenon that an individ-
ual’s likelihood of helping decreases when passive bystanders are
present in a critical situation (Darley & Latane´, 1968; Latane´&
Darley, 1968, 1970; Latane´ & Nida, 1981). Many sad real-life
examples illustrate this effect: In 1964, Kitty Genovese was raped
and murdered in Queens, New York, while several of her neigh-
bors looked on. No one intervened until it was too late.
1
More
recently, in 2009, Dominik Brunner was murdered at a German
train station by two 18-year-olds after he tried to help children who
were attacked by these young criminals. Several passersby wit-
nessed the murder, but nobody physically intervened. In support of
this anecdotal evidence, an influential research program conducted
1
The precise number of bystanders, what they saw, and how they
interpreted the situation are still under dispute (Manning, Levine, & Col-
lins, 2007).
This article was published Online First May 2, 2011.
Peter Fischer, Department of Psychology, University of Regensburg, Regens-
burg, Germany; Joachim I. Krueger, Department of Cognitive, Linguistic, and
Psychological Sciences, Brown University; Tobias Greitemeyer, Department of
Psychology, University of Innsbruck, Innsbruck, Austria; Claudia Vogrincic,
Moritz Heene, Magdalena Wicher, and Martina Kainbacher, Department of Psy-
chology, University of Graz, Graz, Austria; Andreas Kastenmu¨ ller, Department of
Psychology, Liverpool John Moores University, Liverpool, England; Dieter Frey,
Department of Psychology, University of Munich, Munich, Germany.
The meta-analysis was supported by DFG (German Science Foundation)
Project FI 938/2-1.
Correspondence concerning this article should be addressed to Peter
Fischer, Department of Experimental Psychology, Social and Organiza-
tional Psychology, University of Regensburg, 93040 Regensburg, Ger-
many. E-mail: peter.fischer@psychologie.uni-regensburg.de
Psychological Bulletin © 2011 American Psychological Association
2011, Vol. 137, No. 4, 517–537 0033-2909/11/$12.00 DOI: 10.1037/a0023304
517
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