The tendency to rationalize after, for instance, deciding what job to take, which car to buy, or who to marry, is a way to resolve "cognitive dissonance"—a psychological state in which an individual's beliefs, attitudes, and behaviors are at odds, said Louisa Egan, the lead author and doctoral student of psychology.
The dissonance—the anxiety over an appealing road not taken—is uncomfortable and people are driven to resolve these feelings by rationalizing their choices, she said. One way to do this is by downgrading, or denigrating, the option that wasn't chosen.
"For example, if Susan is facing a very hard choice between two cars (A and B), and comes to choose Car A, this act of making this decision will cause her estimate of Car B to drop," Egan said. "She will see it as less attractive than she did originally."
The results in this study were based on experiments where preschool children were asked to choose their favorite stickers, and monkeys selected colored M&Ms. Both were then given the opportunity to choose an option they had previously passed up. Both devalued the option they didn't choose earlier.
"These studies suggest that our motivation to rationalize our decisions may have deep roots over our lifespan and the evolution of our species," Egan said. "The studies also add to a growing body of evidence that we share fundamental cognitive processes with younger humans and nonhuman primates."
Source: YALE University