Final answer:
The bystander effect is a phenomenon in which a witness or bystander does not volunteer to help a victim or person in distress. Darley and Latane's 1968 model explains how the presence of other bystanders can reduce the sense of responsibility to help, leading to a lower likelihood of intervention.
Step-by-step explanation:
The bystander effect is a phenomenon in which a witness or bystander does not volunteer to help a victim or person in distress. It was described by social psychologists Bibb Darley and John Latane in their 1968 model. Their model suggests that the presence of other bystanders reduces the sense of responsibility felt by any one individual to help. This diffusion of responsibility can lead to a decreased likelihood of intervention. For example, in the case of Kitty Genovese's murder, the large number of witnesses led to a diffusion of responsibility and a lack of intervention.