Most research of comparative cognition has focused on the degree to which cognitive phenomena that have been reported in humans, especially children, can also be demonstrated in other animals. The value of such comparative research has not only been the finding that other animals show behavior that is qualitatively similar to that of humans but because the comparative approach calls for the careful control of variables often confounded with the mechanisms being tested, the comparative approach has identified procedures that could also improve the design of research with humans. The comparative approach has also been used to study the degree to which other animals demonstrate human biases and suboptimal behavior (e.g., commercial gambling). When applied to this field of research, the comparative approach has generally taken the position that human biases generally thought to be established by complex social and societal mechanisms (e.g., social reinforcement and entertainment) may be more parsimoniously accounted for by simpler mechanisms (i.e., conditioned reinforcement and positive contrast). When explained in terms of these mechanisms, the results have implications for explaining in simpler and more general terms the results of similar research with humans. Thus, comparative psychology tells us not only about the similarities and possible differences in behavior among species but it also may have implications for our understanding of similar behavior in humans.

Pavlovian associative processes appear to be intimately involved in the acquisition of simultaneous discriminations by pigeons. We have found evidence that in a simultaneous discrimination, value transfers from the positive stimulus (S+) to the negative stimulus (S-) and the basis of that transfer appears to be the higher-order association of the S- with the reinforcer, by way of the S+. Furthermore, the association between the S+ and the S- appears to be bidirectional, occurring in the form of a within event association. In addition, it appears that when pigeons have extended experience with the consequences of responding to the Sstimulus, contrast (the opposite of value transfer) develops between the two (e.g., increasing the value of one, decreases the value of the other). Finally, I suggest that versions of simultaneous discriminations may provide a useful model of several Pavlovian conditioning phenomena including, higher-order conditioning, withinevent conditioning, postconditioning devaluation effects, inhibitory conditioning, potentiation, and perhaps also overshadowing.

Contrast refers to a comparison between two conditions of reward such that the relation between them is magnified (relative to an appropriate control condition). It is an effect that is opposite in direction from generalization (which is a form of averaging). Three kinds of contrast have received substantial empirical attention: Incentive contrast in which a sudden change in reward (either an increase or a decrease) results in an overreaction to the change, relative to a control condition; anticipatory contrast in which an anticipated improvement in reward results in less consumption of an initial reward; and differential or behavioral contrast in which a change in reward associated with one stimulus results in a change in behavior associated with a second stimulus in the opposite direction. Here I discuss a fourth kind of contrast that I call within-trial contrast. In this form of contrast a discriminative stimulus is preferred when it follows a less appetitive event (effort, delay, or the absence of reward). A model of this kind of contrast is proposed that is based on a presumed change in the hedonic state of the organism between the end of the less appetitive event and the reward (or stimulus signaling the reward). It is distinguished from an account based on the relative reduction in delay to reinforcement. Finally, I suggest that a general form of this within-trial contrast may help to explain various complex human social phenomena including cognitive dissonance, justification of effort, the effect of extrinsic rewards on behavior that is maintained by intrinsic rewards, and learned industriousness.

Cognitive mapping implies the development of an internal representation of the spatial relationships among objects in the environment. One can assess the development of a cognitive map by demonstrating that an animal can select, when appropriate, a novel path to reach a goal in the absence of landmarks and when path integration does not provide an adequate account. Rats were trained to find reinforcement in two of three goal boxes in a three-arm maze. In test, the rats were given a choice between two novel paths, one that led to the goal box that had been baited during training, the other that led to the goal box that had been unbaited during training. When they were trained in the absence of distinctive intramaze cues (Experiment 1), no preference was found; however, when distinctive intramaze alley cues were present during training but were unavailable as directional cues during testing (Experiment 2), the rats demonstrated a significant preference for the correct novel path. These results suggest that under appropriate conditions rats are able to form simple cognitive maps of their environment.