AS BACKGROUND INFORMATION, THE AUTHORS LIST THREE ANALYTICALLY DISTINCT PROCESSES THAT MAY ACCOUNT FOR THE FREQUENTLY OBSERVED TENDENCY OF BYSTANDERS TO INHIBIT EACH OTHERS' RESPONSIVENESS IN EMERGENCIES -- SOCIAL INFLUENCE, AUDIENCE INHIBITION, AND DIFFUSION OF RESPONSIBILITY. THE EXPERIMENTERS FOUND THAT HELPING OF THE VICTIM WAS REDUCED BY DIFFUSION OF RESPONSIBILITY AND SLOWED BY NEGATIVE SOCIAL INFLUENCES, BUT WAS INCREASED BY EVALUATION APPREHENSIONS. DIFFERENCES TRACEABLE TO SOCIAL INFLUENCE APPEARED PRIOR TO THOSE FROM THE OTHER PROCESSES. IMPLICATIONS OF THESE FINDINGS FOR THE MEASUREMENT OF HELPING AND THE INTERPRETATION OF BYSTANDER DECISIONMAKING ARE DISCUSSED. (AUTHOR ABSTRACT)...KAP