Responders and nonresponders to cat odor do not differ in other tests of anxiety.

Laboratory-bred rats can be divided into those showing clear innate behavioral responses to the odor of a predator (a cat) and those showing no response. However, these two groups did not differ in their responses to a neutral odor, or in the social interaction or elevated plus-maze tests of anxiety. This suggests a distinction between phobic anxiety (generated by cat odor) and a generalized anxiety state (generated by novelty in the other tests). Trial 2 in the plus-maze generates a state of fear that is distinct from that generated on trial 1, and one suggested to reflect phobic anxiety. Although the groups of cat responders and nonresponders did not differ in their scores on trial 2 in the plus-maze, two clear groups of responders and nonresponders could be identified on this trial (but not on trial 1 or in the social interaction test). This suggests that it is possible to identify bimodal populations of rats in tests of both innate and acquired simple phobias.