The cognitive cost of closeness: Interpersonal closeness reduces accuracy and slows down decision‐making

Abstract Interpersonal closeness increases the overlap between mental representations of the self and the other, thus rendering it more difficult to differentiate between self‐ and other‐related information. We suggest that closeness challenges computational capacity during decision‐making when the decision requires a differentiation between self‐ and other‐related information. Correlational Study 1 showed that when participants imagined engaging in a two‐person economic problem‐solving task with another person, their cognitive performance decreased with increased levels of closeness felt toward their counterpart. Three experiments showed that when participants engaged in the problem‐solving task with a close (vs. a distant) other, they tended to recall the correct solutions less (Study 2), used more time to find the solution (Study 3) and gave less accurate responses under time pressure (Study 4). These four studies are the first to jointly demonstrate that closeness influences interpersonal decision processes by being cognitively more costly.