Choice-induced preference: A challenge for contrast

In his target article, Zentall asks: “to experience cognitive dissonance is it necessary for one to have conflicting beliefs or even beliefs at all?” He then argues that a simple behavioral process, the Within Trial Contrast Effect, may be sufficient to explain observed cognitive dissonance effects in nonhuman animals and possibly humans as well. We agree with Zentall that this effect is sufficient to explain many reported cognitive dissonance effects in nonhuman animals, but question its sufficiency for primate behavior (both monkeys and humans)