Originally posted on July 1, 2014.
In all of recent psychological science, there has been, to my mind, no more provocative studies those by Benjamin Libet. His experiments have seemingly shown that when we move our wrist at will, we consciously experience the decision to move it about 0.2 seconds before the actual movement. No surprise there. But what startled me was his reporting that our brain waves jump about 0.35 seconds before we consciously perceive our decision to move! This “readiness potential” has enabled researchers (using fMRI brain scans) to predict participants’ decisions to press a button with their left or right finger. The startling conclusion: Consciousness sometimes appears to arrive late to the decision-making party.
And so it has also seemed in Michael Gazzaniga’s reports of split-brain patients who readily confabulate (make up and believe) plausible but incorrect explanations for their induced actions. If Gazzinga instructs a patient’s right brain to “Walk,” the patient’s unaware left hemisphere will improvise an explanation for walking: “I’m going into the house to get a Coke.” The conscious left brain is the brain’s public relations system—its explanation-constructing “interpreter.”
So, do Libet’s and Gazzaniga’s observations destroy the concept of free will? Does our brain really make decisions before our conscious mind knows about them? Do we fly through life on autopilot? Are we (our conscious minds) mere riders on a wild beast?
Not so fast. Stanislas Dehaene and his colleagues report that brain activity continuously ebbs and flows, regardless of whether a decision is made and executed. The actual decision to move, they observe, occurs when the brain activity crosses a threshold, which happens to coincide with the average “time of awareness of intention to move” (about 0.15 second before the movement). In their view, the mind’s decision and the brain’s activity, like a computer’s problem solving and its electronic activity, are parallel and virtually simultaneous.
The late neuroscientist Donald MacKay offered a seemingly similar idea: “When I am thinking, my brain activity reflects what I am thinking, as [computer’s] activity reflects the equation it is solving.” The mind and brain activities are yoked (no brain, no mind), he argued, but are complementary and conceptually distinct. As my colleague Tom Ludwig has noted, MacKay’s view—that mental events are embodied in but not identical to brain events—is a third alternative to both dualism and materialism (physicalism).