Latane, B., & Darley, J. M. (1968). Group inhibition of bystander intervention in emergencies. Journal of Personality and Social Psychology, 10(3), 215-221.

Male undergraduates found themselves in a smoke filled room either alone, with 2 nonreacting others, or in groups of 3. As predicted, Ss were less likely to report the smoke when in the presence of passive others (10%) or in groups of 3 (38% of groups) than when alone (75%). This result seemed to have been mediated by the way Ss interpreted the ambiguous situation; seeing other people remain passive led Ss to decide the smoke was not dangerous.

 

 

Latane, B., & Darley, J. M. (1968). Group inhibition of bystander intervention in emergencies. Journal of Personality and Social Psychology, 10(3), 215-221.

http://dx.doi.org/10.1037/h0026570