Can squirrel monkeys learn an AB(n)A grammar? A re-evaluation of Ravignani et al. (2013).

Ravignani et al. (2013) habituated squirrel monkeys to sound sequences conforming to an AB(n)A grammar (n = 1, 2, 3), then tested them for their reactions to novel grammatical and non-grammatical sequences. Although they conclude that the monkeys "consistently recognized and generalized the sequence AB(n)A," I remark that this conclusion is not robust. The statistical significance of results depends on specific choices of data analysis, namely dichotomization of the response variable and omission of specific data points. Additionally, there is little evidence of generalization to novel patterns (n = 4, 5), which is important to conclude that the monkeys recognized the AB(n)A grammar beyond the habituation patterns. Lastly, many test sequences were perceptually similar to habituation sequences, raising the possibility that the monkeys may have generalized based on perceptual similarity rather than based on grammaticality.