What external factor did Piliavin investigate in relation to helping behavior?

Piliavin's investigation into helping behavior primarily focused on the type and race of the victim. He sought to understand how these external factors influenced bystanders' willingness to help someone in distress. The study included a staged incident on a subway where a participant would collapse, and researchers varied the race of the victim and whether the victim appeared to be ill or drunk. The results showed that characteristics of the victim, such as their race and perceived condition, significantly affected the speed and likelihood of help from bystanders. This highlights the crucial role that perceptions about the victim play in social situations, which is fundamental in the study of social psychology and altruism.

The other options, while relevant in broader discussions, did not form the central focus of Piliavin's study. For instance, the location of the incident could influence helping behavior in general, but Piliavin's experiments were specifically designed to examine the impact of victim characteristics. Similarly, the presence of law enforcement and socioeconomic status were not the primary variables tested in his experiments. This specificity underscores the significance of the type and race of the victim in understanding helping behavior as revealed by Piliavin’s research outcomes.