We attempt to understand the relationship between stress, coethnic preference, and prosocial behavior in sub-Saharan Africa. Observational studies have shown that ethnic identity has significant implications for social, economic, and political outcomes in this region. However, laboratory experiments often fail to find evidence of co ethnic preference in economic exchange games. The study explores the possibility that stress may strengthen co ethnic preference, as laboratory studies are conducted in low-stress environments, while observational studies reflect decisions made under stress. The researchers manipulate cortisol levels, a marker of stress, through the administration of hydrocortisone pills, and assess participants’ behavior in behavioral games and social proximity surveys.