The first thing to notice is that Mr. Bush made a very specific error. He did not declare himself African-American or Native American. He declared himself Hispanic. Mr. Bush’s wife is from Mexico. Might her Hispanic identity have played a role in his voter registration error?

Research in social psychology suggests that it could have. Consider a 1991 study about the cognitive effects of being in a close relationship. Married research participants were asked to complete a questionnaire that assessed whether they possessed each of 90 personality traits and whether their spouses possessed each of those same traits. Next, to test their gut-level certainty about these assessments, the participants performed a computerized task in which they indicated, as rapidly as possible, whether they possessed each of the 90 traits. The computer measured response times in milliseconds.

How did they fare at the computerized task? The participants were significantly faster at determining whether a given trait applied to them if it applied to both them and their spouses — or neither them nor their spouses — than if it applied to one of them but not the other.