Frequency-based organization of speech sequences in a nonhuman animal.

A recurrent question regarding language acquisition is the extent to which the mechanisms human infants use to discover patterns over the linguistic signal are highly specialized and uniquely human, or are the result of more general mechanisms present in other species. Research with very young infants suggests that they are able to use the relative frequency of elements in a linguistic sequence to infer word order. Here we ask if this ability could emerge from grouping biases present in nonhuman mammals. We show that animals discover differences in the frequency of elements in a sequence and can learn the relative order of frequent and infrequent elements. Nevertheless, in animals, relative frequency does not appear to be overridden by other cues that have been shown to be important to human infants, such as prosody. Our results demonstrate that the basic mechanism that allows listeners to extract ordering relations based on frequency is shared across species.