Proprioception refers to the unconscious perception of movement and spatial orientation. Individuals without it lack the ability to direct the body's various parts to move and must resort to using visual clues. Impaired proprioception is routinely tested by police officers via a "field sobriety test," which asks individuals suspected of being under the influence of alcohol or other drugs to perform a set of tasks (such as touching their nose with their finger) with their eyes closed. In more severe cases, individuals lacking proprioception are unable to stand or walk or move their limbs without conscious effort.