Vection

Vection is the conscious perception of self-motion induced by visual stimuli. It occurs when a person observes motion in the surrounding environment, such as a rotating room, a moving tunnel, or expansive optic flow, while the observer remains physically stationary. Vection can be strong enough to feel as if the body is actually moving through space, even though no actual translation or rotation has occurred.

Visually induced self-motion results from the brain's integration of sensory signals. Visual motion information from the retina, processed in areas such as MT/V5, interacts with vestibular and proprioceptive inputs. When visual cues dominate or conflict with non-visual cues, vection emerges. The strength and onset of vection depend on factors including display size and field of view, the intensity and coherence of the moving visual pattern, the speed and direction of motion, luminance, contrast, and the observer's attention and expectations.

Common forms include circular vection, caused by rotation around a vertical axis, and linear vection, caused by forward or backward motion. Vection onset is variable, typically taking several seconds, and is often rated on subjective scales. Objective measures include changes in postural sway and, in some cases, changes in autonomic indicators.

Vection is a central concept in vision science, virtual reality, and simulator design. It helps explain why immersive displays can produce a sense of movement without actual locomotion and why mismatch between visual and vestibular inputs can lead to discomfort, such as simulator sickness. It is also used experimentally to study multisensory integration and self-motion perception.