Tests indicate that wholly arbitrary syntactic rules could be understood and that an understanding of the function of words occuring early in a sentence could be carried out by the dolphin on the basis of succeeding words. Some comparisons were given of the dolphins' performances with those of language-trained apes and of young children on related or relevant language tasks.
The ability of two bottlenosed dolphins Tursiops truncatus to understand imperative sentences expressed in artificial languages were studied. One dolphin (Phoenix) was tutored in an acoustic language whose words were computer-generated sounds presented through an underwater speaker. The second dolphin (Akeakamai) was tutored in a visually-based language whose words were gestures of a trainer's arms and hands.
The words represented agents, objects, object modifiers, and actions and were combinable, according to a set of syntactic rules, into hundreds of uniquely meaningful sentences from two to five words in length. The sentences instructed the dolphins to carry out named actions relative to named objects and named modifiers; comprehension was measured by the accuracy of response to the instructions and was tested within a format that controlled for context cues, for other nonlinguistic cues, and for observer bias.
Comprehension, at levels far above chance, was shown for all of the sentence forms and sentence meanings that could be generated by the lexicon and the set of syntactic rules. The comprehension approach used was a radical departure from the emphasis on language production in studies of the linguistic abilities of apes; the result obtained offer the first convincing evidence of the ability of animals to process both semantic and syntactic features of sentences.