Building on past research, they explored self-positivity and self-negativity biases. Such research has shown, for example, that symptoms we perceive to be indigestion in a stranger are often thought to be a possible heart attack in ourselves (self-negativity). Conversely, we can underestimate our risk for many common conditions like sexually transmitted diseases (self-positivity). …

When told the disease base rate was high, but risky behavior likelihood was low, the subjects said they were less vulnerable to risk than others (who engaged in the same behaviors) were. That’s a self-positivity bias. But when told the base rate of HIV was low, but risky behavior likelihood was high, the participants judged themselves more vulnerable than others. That’s self-negativity. …

His findings, published this month in the Journal of Consumer Research, show that the advantage of seeing a real doctor isn’t just because he or she is an expert. It’s also that they aren’t you.