Visual and olfactory oddity learning in rats: What evidence is necessary to show conceptual behavior?

Experiment 1 involved the use of plastic and wooden objects and trial-unique problems. The rats performed successfully on nonconceptual oddity problems given before and after conceptual training, showing that the testing conditions were suitable, but they showed chance performances on the trial-unique problems. Experiment 2 involved the use of olfactory discriminanda. Five pretraining problems and 300 unique five-trial problems were presented. Two of 3 rats performed better than chance on Trial 2 and on Trials 3–5, but all performed at chance levels on Trial 1 throughout. The data suggest that the rats responded to specific odors on Trials 2–5 following the Trial 1 experience, as opposed to respondingconceptually to the “odd” odor. Had they responded conceptually to odd odors, they should have performed better than chance on Trial 1. These findings and the general logical argument that they support are considered in the context of the numerous inconclusive reports of the use of the oddity concept by nonprimate animals.