Encoding Structural Ambiguity in Rat Serial Pattern:The Role of Phrasing

Rats, like humans, appear sensitive to the structure of the elements of sequences. In the present study, we examined the effects of phrasing a structurally ambiguous pattern as either a series of “runs” or “trills.” A pattern phrased as runs was easier to learn than when it was phrased as trills, a result that resembles a similar “runs bias” reported in the human sequential learning literature. Whereas rats learning the runs-phrased pattern showed rapid learning and little tendency to make trills errors, rats learning the trills-phrased version of the pattern produced inflated rates of both trills and runs errors. The results show that rats represented the runs- and trills-phrased versions of the pattern differently. These results add to the evidence that, in addition to serving as discriminative cues, phrasing cues can bias pattern perception in rat serial pattern learning resulting in memorial representations characterized by multiple interpretations of the same pattern. The results also fit well with recent behavioral and neurobehavioral studies implicating multiple concurrent psychological and neural processes in rat serial pattern learning.