Leah Jordan

Honors in Psychology

Major: Psychology Minor: Biology

Supervisor: Katherine Bruce, Psychology

List Linking as a Tool to Test Transitive Inference in Rats

Transitive inference, along with other abstract concepts, has been considered a characteristic unique to humans. Transitive inference is demonstrated when one learns that A is related to B and B is related to C, and then infers that A is related to C. Rats have been shown to demonstrate transitive inference after being trained on four overlapping simple odor discriminations; when trained only on odor pairs A>B, B>C, C>D, and D>E, they spontaneously show transitive inference (e.g., A>C and B>D; Davis 1992; Dusek & Eichenbaum 1997). In the present study, we extend these findings to a novel apparatus and add a list-linking procedure similar to that studied by Treichler et al. (1996) in monkeys. Rats are trained on two separate lists of odor pairs (A-E and F-J) and then the lists are linked through training on EF. Using two lists allows testing for transitive inference using many novel combinations of pairs across and within lists (for example B-H and G-I). Three rats have responded with transitive inference consistently (over 90% of the time) when tested with novel combinations of pairs within lists and two rats have completed the final test after list linking, performing above 75% on between list novel combinations and 70% or above on within list combinations. Transitive inference has been seen across several species and may be evidence of an adaptive process used in establishing social hierarchies among non-humans.