News & Media
Neuroscience 101 - How Do Our Thoughts Cause Our Actions?
Consider this: you think to reach out to pick up a coffee cup, and then you do it. What just happened? Well that’s obvious. Your conscious thought caused your action. You perceive conscious will as a force, freely directing your decisions and actions. This feeling is undeniable. But wait a minute, how can something as weightless and intangible as a thought activate the nerve cells in the part of your brain that controls arm movement? The fact of the matter is, from the point of view of modern neuroscience, it really makes more sense to think of the whole process the other way around; the sensation of conscious will is a consequence or side-effect of the decision-making activity of the brain. Conscious will is a feeling, not a force.
The proposition that our conscious thoughts don’t provide the initial oomph that leads to our actions – that they are effects not causes – makes absolutely no intuitive sense; nevertheless, it's backed up by experimental data. In 1983 the neurophysiologist Benjamin Libet recorded electrical activity in the brains of human subjects, who were instructed to lift a finger whenever the mood struck them. Libet showed that the subjects’ feelings of consciously willing these voluntary movements appeared several tenths of a second after the start of brain activity that predicted the movements, but nevertheless just before the movements actually took place. In other words, the conscious feeling of acting “on-purpose” was sandwiched between the unconscious initiation of action by the brain and the actual finger movement. Think again of the example in which you voluntarily reach out to pick up a coffee cup. Libet’s result suggests that your decision to move is made by unconscious brain processes and that you don’t become consciously aware of what you are going to do until a fraction of a second after the decision has been made, but just before the movement begins. More recently, using functional MRI, a much more sophisticated approach for assessing brain activity, John-Dylan Haynes and his colleagues showed that activity in a region of the prefrontal cortex (the brain area just above the eyes) occurred up to 10 seconds before human subjects were consciously aware that they had decided to press a button with either their left or right index finger. Apparently, the subjects’ brains had decided which finger to use many seconds before they consciously knew what they were going to do.
How can it be that our conscious intentions don’t begin the chain of events that cause our voluntary actions, when we feel so certain that they do? Harvard psychologist Daniel Wegner suggests that this “illusion” occurs because our sense of conscious will is related to our actions in three ways: priority (the thought precedes the action), consistency (the thought is consistent with the action) and exclusivity (there are no other potential causes). The thought to reach for the remote control pops into your consciousness, and then, a fraction of a second later, you do in fact reach for the remote, so you assume that the conscious thought caused the action. As Wegner puts it, “we develop the sense that [our conscious] intentions have causal force even though they are actually just previews of what we may do.” According to this idea, conscious will is a side-effect of the decision-making activity of the brain. It’s like the foam on top of a glass of beer, or the heat emanating from a computer. It doesn’t do anything, it just feels like something.
If conscious will is a side-effect of the brain activity that initiates action, then it should be possible under the right circumstances to separate voluntary action from the sensation of personal agency. Wegner sites numerous situations in which this happens. For example, individuals lose the sense of conscious control over their own voluntary actions when they are hypnotized, when they believe they are possessed by demons and when they speak in tongues. A striking and poignant example of the loss of conscious awareness of personal agency is facilitated communication, in which trained facilitators were completely convinced that they were enabling patients with autism and other disorders to type out messages by steadying the patients’ hands on a keyboard. Careful analysis has revealed that it was the facilitators themselves who were initiating all the typing. The key idea here is that the facilitators weren’t lying. Their belief in the process and their strong desire help their patients communicate uncoupled their voluntary actions (for example, typing out messages, such as “”I AM NOT A UTISTIC OH THJE TYP.”) from their feelings of personal agency.
Our minds have evolved to see ourselves and other apparently sentient agents, be they other human beings, pets, animated robots or geometric shapes darting around a video screen, as having minds, and as capable of free, willful action. Now modern neuroscience is deconstructing this intuition and showing how its elements follow the same laws of cause and effect as everything else in the universe. We are in the midst of a revolution in our understanding of ourselves as profound as the revolutions brought on by Copernicus and Darwin. Where will it lead? Stay tuned.
