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Free Will and Action

According to neuroscientist Benjamin Libet (1916-2007), our brains adjust how we experience ourselves as acting in the world to give an illusion of doing so freely and in real time. Libet performed experiments on willed action that many took as evidence against free will. Imagine being part of one type of experiment, where Libet places you in front of a projected clock with a moving dot as a hand.

You are asked to—whenever you feel comfortable—flick your wrist and note where the dot was when you decided to. During this exercise, Libet monitors the supplementary motor area for a readiness potential—an electroencephalographic (EEG) footprint of the brain, getting ready to move the body. Libet found that these readiness potentials preceded awareness of any decision to move by, on average, 0.3 seconds (Libet et al. 1982). The brain apparently began the movement process ahead of conscious awareness.

Ordering of Events

Libet also experimented with conscious, open-brain surgery patients just about to go into surgery and found that the brain backdated tactile events (Libet et al. 1979). As discussed in chapters “Consciousness Rediscovered” and “Consciousness as a Modern Mystery”, the somatosensory cortex responds to tactile stimulation. We know what parts of the body, such as a finger, are associated with what cortex. One can stimulate appropriate cortical areas with an electrode to give a sensation of—let us say—touching the tip of the right index finger. Libet explored the brain’s interpretation of tactile sensation events caused by direct brain stimulation as compared with those caused by touch. He found that events from the body were backdated as compared with direct brain stimulation events. Brains make time-delay compensations depending on the signaling source, and so normal somatosensory activations caused by touch take no longer to experience than those caused by cortex stimulation. Even if it takes half a second to notice a touch, one experiences it as occurring at a relatively accurate point in time.

Libet also found that signals could partly cancel each other out, given the right time intervals, so a touch to the body and corresponding cortical stimulation were experienced as the same single touch. Libet’s research on perception and action opens up questions about how we experience ourselves as acting freely in a coherent world.

 
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