The Contagiousness Bias

In five studies, we find that people infected with a contagious disease perceive themselves to be less contagious than a stranger with the same disease. We label this pattern of judgment the “contagiousness bias” and find that it occurs because people cope with being sick by downplaying the severity of their own (vs. another person’s) illness. Across communicable diseases (e.g., cold, COVID-19, STIs), we document the contagiousness bias and show that perceptions of severity mediated this effect (Studies 1, 5). In line with the notion that people downplay the severity of their own (vs. another person’s) illness as a coping mechanism, we show that disease hypotheticality moderates the effect, such that the bias attenuates when people merely imagine being sick because do not need to employ any coping mechanisms for a hypothetical illness (Study 2). The contagiousness bias persists even in the presence of explicit information about one’s own contagiousness(Study 3) and creates a self-other difference in attitudes toward complying with health recommendations (I will not necessarily comply, but others should; Study 1, 3). Finally, we show that this bias is moderated by the extent to which others are included in one’s self-concept: It extends to close friends who are deemed also less contagious than a stranger (Study 4), and it attenuates among participants whose self-construal is more interdependent than independent(Study 5). We discuss the theoretical and practical implications of these findings.