Non-attention-getting calls produced during the uptake period in the COM and RES conditions.

These sounds were characterized by the fact that they did not occur within the context of requesting food from a human experimenter, and included pant hoots, barks/grunts, grooming vocalizations, whimpers and screams. Pant-hoots (PH) are voiced on both inhalation and exhalation, may incorporate a series of “hoo” sounds escalating to a climactic scream or piercing “ahh” vocalization, and seem to be directed to distant recipients. Barks and grunts (B/G) are relatively short vocalizations that can be tonal (barks) or noisy (grunts), and are often produced in a series. These calls are associated with the anticipation of eating or receiving food, or other positive experiences, as well as during introductions/reunions with social partners.Grooming calls (GR) are unvoiced sounds that include teeth chomping/clacking, and occur during grooming bouts with another individual or during autogrooming. Screams (S) are relatively loud, high-pitched, voiced shrieks and at its most intense can be raspy or even hoarse sounding. Screams usually occur in contexts of fear, submission, or distress. Whimpers (W) are similar to modulated, high-pitched ‘hoo’ sounds or crying and often progresses into screams. Whimpering occurs in chimpanzees of all ages during distress or fear and by infants when being weaned.