Evidence for human-like conversational strategies in an African Grey parrot's speech
Colbert-White, Erin Natannie
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Researchers have established many similarities in the structure and function of human and avian communication systems. This dissertation investigated one unique nonhuman communication system—that of a speech-using African Grey parrot. In the same way that humans learn communicative competence (i.e., knowing what to say and how given a particular social context), I hypothesized that Cosmo the parrot’s vocalizations to her caregiver, BJ, would show evidence of similar learning. The first study assessed turn-taking and the thematic nature of Cosmo’s conversations with BJ. Results confirmed that Cosmo took turns during conversations which were very similar to humans’ average turn-taking time. She also maintained thematically linked dialogues, indicating strategic use of her vocal units. The second study investigated Cosmo’s ability to take BJ’s auditory perspective by manipulating the distance between the two speakers. As predicted, Cosmo vocalized significantly more loudly when her owner was out of the room, and those vocalizations classified as social (e.g., kiss sounds) were uttered significantly more loudly than vocalizations which were considered nonsocial (e.g., answering machine beep sounds). These results suggested Cosmo may be able to take the perspective of a social partner, an ability others have documented in Greys using alternative tasks. Strategic use of vocalizations was revisited in Studies 3 and 4. The third study examined Cosmo’s requesting behavior by comparing three separate corpora (i.e., bodies of text): Cosmo’s normal vocalizations to BJ without requesting, Cosmo’s vocalizations following a denied request, and Cosmo’s vocalizations following an ignored request. Cosmo treated all three speech contexts differently; distributions and rate of use of speech, nonspeech, social, and nonsocial vocalizations differed significantly. The results of the fourth study supported the third study’s findings. While Cosmo did not use phrases which BJ classified as “jokes” significantly more often following a refused request (which would indicate strategic use of vocalizations to manipulate affect), her vocalization patterns indicated that she perceived the refusal condition as being different from normal conversation. While the results can be compared to child sociocognitive development, my findings may also be extended to wild Greys’ communication system to learn more about the species’ natural capabilities.