Nodding

Nodding is the action of moving the head up and down, typically as a brief flexion of the neck followed by return to an upright position. It is one of the most common nonverbal cues in human communication. A nod generally signals assent, agreement, acknowledgment, or encouragement, but its meaning is highly dependent on context, accompanying speech, and cultural norms.

The movement is produced by contraction of neck muscles such as the sternocleidomastoid and the muscles of the upper back and neck. It is coordinated by the motor cortex, basal ganglia, and brainstem and can be voluntary or reflexive. Nods can be shallow or full, frequent or pause-like, and may be used in rapid back-channel signaling during dialogue.

In social interaction, nodding acts as a back-channel cue that shows attention and comprehension and can encourage the speaker to continue. Overly frequent nodding or odd timing can signal impatience, fatigue, or social discomfort in some contexts. The interpretation of nodding varies across cultures; in many societies it conveys agreement, while in others contingent signs or accompanying gestures are important for disambiguation.

Nodding off refers to falling asleep while staying seated or awake. Nodding syndrome is a rare neurological condition characterized by repetitive nodding head movements, primarily affecting children in certain regions of Africa; etiology is not fully understood.

In research and technology, nodding is studied as a nonverbal cue in psychology and human-computer interaction and can be detected with video or sensor-based methods; it is sometimes modeled in animation and robotics to convey agreement or attention.