Neuro term. 1. A nonverbal sign sent, as opposed to one received (see AFFERENT CUE). 2. An outgoing sign produced, e.g., by a body movement, clothing cue, consumer product, glandular secretion (e.g., apocrine odor, sweaty palms, tears), hair style, nonverbal vocalization (e.g., cry, laugh, whine), posture, recipe (e.g., Big Mac, Coca-Cola, shrimp cocktail), or speech error.
Usage: Conceptually, efferent and afferent reflect the two sides of every nonverbal sign: (1) egress (as an out-bound cue to be produced) and (2) ingress (as an in-bound cue to be processed).
The Shanghai gesture. "The gesture [see epigraph above] is useful. It is comforting. It does something for you and to you, because the world cannot answer--in kind--if you make the gesture first" (Williams 1926:8).
Neuro-note: Efferent cues reflect a. inner thoughts (produced, e.g., in tandem with the speech areas), and b. inner workings of the nonverbal brain.
See also CUE, INFORMATION, MESSAGING FEATURE.
YouTube Video: See how many nonverbal signs, signals, and cues you can see in "The Shanghai Gesture," an elegant 1941 motion picture.