Aging enhances cognitive biases to friends but not the self.

We measured changes in self and friend biases in perceptual matching in young and older participants. Participants learned associations between neutral geometric shapes and three personal labels (You, Friend, or Stranger), representing themselves, their named best friend, and a stranger not corresponding to anyone they knew. They then responded whether the shapes and labels matched or mismatched. In addition, participants reported the perceived personal distance between themselves, their best friend, and a stranger. Relative to young participants, older adults showed an increased bias toward matching their friends over strangers, whereas the bias toward the self over friends tended to decrease. Equivalent results occurred for a perceived personal distance measure, and, on measures of perceptual sensitivity with older participants, the personal distance between friends and strangers correlated with the friend bias in matching. These results indicate that the social bias toward a familiar best friend increases with age and modulates perceptual matching.