The bystander effect

The bystander effect is also called the Genovese Effect, Genovese Syndrome, or diffusion of responsibility.
The theory behind this phenomenon is that an individual’s likelihood of helping a person in need is directly tied to the number of people witnessing the person’s need at the same time.
According to the psychological literature on this phenomenon, a person is far less likely to help someone else in need if he or she is not the sole witness to the person in need.
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diffusion
拡散
witness
目撃者
傍観者効果（bystander effect）とは、社会心理学の用語であり、集団心理の一つ。
ある事件に対して、自分以外に傍観者がいる時に率先して行動を起こさない心理である。
傍観者が多いほど、その効果は高い。