International Journal of Comparative Psychology

C. Lloyd Morgan is widely credited as the “father of comparative psychology” due to his contribution of guidelines for the psychological interpretation of animal behavior. Many modern comparative psychologists believe that constraints encouraged by Morgan are now obsolete and some assert that adherence to the canon restricts further progress in the field. Nonetheless, Morgan’s guidance continues to be important in comparative psychology. A review of Morgan’s canon, its historical misuse, and consideration of popular alternatives reinforce Morgan’s role in comparative psychology. A recent model of cognitive evolution highlights the importance of Morgan’s guidelines and an illustration of the continued usefulness of the canon is given in the context of investigations of theory of mind in chimpanzees.

Animal behavior studies of the 19th century were characterized by an appeal to anthropomorphic attitudes, which were resolutely challenged beginning with the start of the 20th century, particularly by the forerunners of what became the behaviorist school. The ethological school founded by Tinbergen and Lorenz also rejected appeals to human-like cognitive abilities. In the l970s, under the leadership of the physiologist, Donald Griffin, animal cognition was again admitted into “respectable” ethological company, leading to a strong critique by another eminent physiologist, John Kennedy. (The influence of Tolman had previously made many comparative psychologists receptive to this possibility). Recent studies based upon developments on direct recordings of brain activity now suggest that Tolman and Griffin’s prescience will carry the day.

Responsiveness to ethanol is markedly affected by fetal or infantile experiences with the drug. Yet, there is minimal information available relative to the interaction of these experiences. This study focused on such interaction and on the impact of ethanol intoxication on maternal care. Water or subnarcoleptic doses of ethanol were administered to pregnant rats during late gestation (2.0 g/kg) and/or while nursing (2.5 g/kg). Infantile intake of a low concentrated ethanol solution (0.22% v/v) was assessed during postpartum days (PPDs) 15 and 16. Following the first intake test, infantile intake was explicitly paired with water or varying ethanol doses (0.5, 1.0, or 2.0 g/kg) to assess possible associative learning comprising ethanol’s sensory and unconditioned properties. The interaction between ethanol pre- and postnatal treatment resulted in heightened ethanol reactivity as assessed through intake scores, particularly during PPD 16. Maternal treatments failed to affect associative learning mediated by ethanol. Ethanol was also found to disrupt both maternal retrieval and crouching latencies. This effect was markedly reduced when females had experienced ethanol during gestation, a phenomenon indicative of tolerance. Sequential experience with ethanol during gestation and nursing facilitates subsequent responsiveness to minimal ethanol concentrations, without affecting the sensitivity to the unconditioned effects of the drug as evaluated through associative learning procedures.

In two experiments in a virtual pool the participants were trained to find a hidden platform placed in a specific position in relation to one (Experiment 1) or two (Experiment 2) objects; then, all the participants received a test trial, without the platform, and the time spent in the segment where the platform should have been was measured. In Experiment 1, groups differed in the distance between the landmark and the hidden platform. Test results showed that the control acquired by the landmark was different depending on its relative distance from the platform: Closer landmarks acquired a better control than distant ones. In Experiment 2, two objects, B and F, were simultaneously present during acquisition. Object B was just above the hidden platform (i.e., a beacon for the platform) while object F was above the edge of the pool (i.e., a frame of reference). On the test, the spatial location of B in relation to F was manipulated in the different groups and a generalization gradient was found: Participants spent more time in the segment where B was when B was in front of F (training position), and this time decreased symmetrically with distance of B from F. The two experiments provide convergent evidence of spatial learning effects in a virtual task with humans.

An experiment assessed the impact of varying levels of interference on reinstatement in human causal learning. Participants studied fictitious customer files to learn relationships between foods and gastric illness in acquisition. During interference training, a new relationship was learned between the same foods and a different illness over 12, 15, or 18 trials. Prior to the test, presentations of either outcome in the absence of information about the food led to losses of the second-learned information and recovery of that learned first. This effect was reduced as the number of interference trials increased. Results are discussed in terms of their implications for theories of reinstatement and of the parallels with animal studies on renewal.

Rats were used to examine the effects of a surprising post-CS event on reacquisition of an extinguished conditioned taste aversion. One flavor CS was paired with LiCl and then followed by many CS-alone extinction trials. Following these extinction trials, subjects received the CS paired again with LiCl to assess the extent of reacquisition. For some subjects, the final extinction exposure was immediately followed by a surprising second flavor CS. The surprising event did not influence the degree of reacquisition. Additional results found that the second flavor did influence habituation of neophobia to a flavor showing that the event does influence consumption in some circumstances. These results are discussed with respect to the role of attention on extinction and reacquisition of a conditioned taste aversion.