Final answer:
Chimpanzees can understand visual cues such as an extended arm or flat hand as a stop signal, particularly if trained or regularly exposed to such human gestures.
Step-by-step explanation:
Yes, chimpanzees can understand the idea of an extended arm and a stop signal with a flat hand, to a certain extent, as various studies on nonhuman primate communication suggest. Chimpanzees, along with other great apes like gorillas, bonobos, and orangutans, have been taught to use gestures and signs to interact with humans and to refer to objects in their environment. These abilities suggest that great apes have the capacity for a protolanguage, a precursor to fully developed human language. In terms of visual communication, which is common among most primates, chimpanzees can also use facial expressions, such as a fear grin, to convey emotions, and raised arms can signal to other chimpanzees to maintain distance. Therefore, the movement of an extended arm or a flat hand as a stop signal could potentially be within the comprehension of a chimpanzee, particularly if they have been exposed to such gestures regularly through interaction with humans.