The behavior of people who remain committed to a choice, even when it is clear that an alternate choice would be a better option, has been a perplexing phenomenon to psychologists and economists. For example, people will continue to wait in the slow line at a grocery store, stick out an unhealthy relationship, or refuse to abandon an expensive, wasteful project—all because such individuals have already invested time, effort, or money. This well-known cognitive phenomenon termed the “sunk cost fallacy” has long been considered a problem unique to humans. New research has discovered that humans are not the only species that share these economically irrational flaws.