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Simple Summary: Chimpanzees Tatu and Loulis use signs of American Sign Language. This study presents sign use over 8 years while living at the sanctuary of the Fauna Foundation. They used a majority of the signs in their base vocabulary each year in a variety of communicative functions. Adult chimpanzees Tatu and Loulis lived at the Fauna Foundation sanctuary. They had acquired signs of American Sign Language (ASL) while young and continued to use them as adults. Caregivers with proficiency in ASL maintained daily sign language records during interactions and passive observation. Sign checklists were records of daily vocabulary use. Sign logs were records of signed interactions with caregivers and other chimpanzees. This study reports sign use from eight years of these records. Tatu and Loulis used a majority of their base vocabularies consistently over the study period. They used signs that they had acquired decades earlier and new signs. Their utterances served a variety of communicative functions, including responses, conversational devices, requests, and descriptions. They signed to caregivers, other chimpanzees, including those who did not use signs, and to themselves privately. This indicates the importance of a stimulating and interactive environment to understand the scope of ape communication and, in particular, their use of sign language. [ABSTRACT FROM AUTHOR]

Questions serve to initiate and continue conversation as well as to gain information and introduce new topics. In signed languages a question can be signaled by modifying the content of an utterance or by coordinating the use of nonmanual markers (e.g., the questioning look) and manual modulation (e.g., holding the sign for an extended duration). Cross-fostered chimpanzees, who use signs of American Sign Language (ASL), have demonstrated behaviors that appear in human conversation, including question-answer exchanges. The current study describes the production of questions by signing chimpanzees in a conversational context and offers a methodology for quantifying the relationship between nonmanual markers and manual modulation involved in interrogative utterances. [ABSTRACT FROM AUTHOR]

Pretend play is well studied in human children and is thought to be associated with symbolic thought and theory of mind. There are many descriptions of pretend play in chimpanzees and other apes but few systematic studies. This study was a systematic sampling of videotapes for instances of pretend play in chimpanzees who have acquired American Sign Language. There were two sampling methods. The first sample of 17 hours 36 minutes and 26 seconds of videotape contained five instances of pretend play. The second sample of 50 hours 16 minutes and 41 seconds contained 16 instances. The instances fell into four different categories; substitution, attribution of function, animation, and insubstantial situation attribution. [ABSTRACT FROM AUTHOR]

Speech act theory describes units of language as acts which function to change the behavior or beliefs of the partner. Therefore, with every utterance an individual seeks a communicative goal that is the underlying motive for the utterance's production; this is the utterance's function. Studies of deaf and hearing human children classify utterances into categories of communicative function. This study classified signing chimpanzees' utterances into the categories used in human studies. The chimpanzees utilized all seven categories of communicative functions and used them in ways that resembled human children. The chimpanzees' utterances functioned to answer questions, request objects and actions, describe objects and events, make statements about internal states, accomplish tasks such as initiating games, protest interlocutor behavior, and as conversational devices to maintain and initiate conversation. [ABSTRACT FROM AUTHOR]

Conversational interactions depend on partners making contingent responses. This experiment examined the responses of five chimpanzees (Pan troglodytes), Washoe, Moja, Tatu, Dar and Loulis, to four conversational conditions. Following the chimpanzee’s request, a human interlocutor either: (1) complied with the request, (2) provided an unrequested item or activity, (3) refused to comply or (4) did not respond to the request. The chimpanzees’ responses were contingent on the conversational input of the interlocutor. When their requests were satisfied, the chimpanzees most often ceased signing. However, when their requests were misunderstood, refused or not acknowledged, the chimpanzees repeated and revised. This pattern of responses is comparable to patterns of conversational responses in human children. Keywords: chimpanzees; American Sign Language; requests; pragmatics; conversation; gesture; communication; Pan troglodytes [ABSTRACT FROM AUTHOR]