Document Type


Date of Degree Completion

Fall 2018

Degree Name

Master of Science (MS)


Primate Behavior

Committee Chair

Mary Lee Jensvold

Second Committee Member

Heidi Shaw

Third Committee Member

Rodrigo Rentería-Valencia


Native signers of American Sign Language produce interrogatives by holding signs for an extended duration while employing the questioning look. The questioning look is defined as raised eyebrows, a tilted head, and direct eye contact maintained for the duration of the utterance. Chimpanzees who communicate using signs have demonstrated modulation of signs including held sign, raised brow, and eye gaze. The present study used archived video data to compare the duration of signs when the chimpanzees did or did not employ the questioning look. In both single and multi-sign utterances, the chimpanzees held their signs for a mean of 0.6 and 0.4 s longer, respectively, with the questioning look. The chimpanzees held signs for an equal duration regardless of the sign’s position within an utterance. The present study contributes to the evidence that the chimpanzees modulate their signs and use signs conversationally. The present study also provides detail on the pragmatics and patterns of modulation. Held sign and raised brow can occur separately under many contexts, however when used together a signer produces an interrogative.