Does a particular hormone actually cause a behaviors' or just make it more likely? *

Free will is the idea that we have the power to choose our actions and shape our destiny, without being constrained by external factors such as physical laws, fate, or divine intervention. However, many scientists and philosophers have challenged this notion, arguing that free will is an illusion and that our decisions are determined by prior causes beyond our control. In this essay, I will examine the evidence and arguments from three prominent researchers who have studied the neural and biological basis of human behavior: Michael Gazzaniga, Benjamin Libet, and Robert Sapolsky.

Michael Gazzaniga is a professor of psychology and neuroscience at Stanford University, who is known for his pioneering work on split-brain patients. These are people who have undergone a surgical procedure to sever the corpus callosum, the bundle of nerve fibers that connects the two hemispheres of the brain. Gazzaniga and his colleagues found that when the two hemispheres are disconnected, they can act independently and sometimes even in conflict with each other. For example, in one experiment, a split-brain patient was shown a picture of a chicken claw in his left visual field, which is processed by the right hemisphere, and a picture of a snow scene in his right visual field, which is processed by the left hemisphere. He was then asked to choose from a set of objects the one that was most related to what he saw. He picked a chicken with his left hand, which is controlled by the right hemisphere, and a shovel with his right hand, which is controlled by the left hemisphere. When asked to explain his choices, he said that he picked the chicken because it goes with the claw, and the shovel because "you need a shovel to clean out the chicken shed".

Gazzaniga argued that this shows that the left hemisphere has a special ability to generate explanations and narratives for our actions, even when they are not based on the true causes. He called this the "interpreter" function of the left hemisphere, and suggested that it creates the illusion of free will by rationalizing our behavior after the fact. He wrote, "The left hemisphere's delusion that it is in charge becomes our delusion. The left hemisphere is a spin doctor, not the commander in chief." 2

Benjamin Libet was a neuroscientist who conducted a famous experiment in the 1980s that seemed to show that the brain initiates voluntary actions before we are consciously aware of them. In his experiment, he asked participants to perform a simple task, such as pressing a button or flexing their wrist, at a time of their own choosing. He measured their brain activity using an electroencephalogram (EEG), and their subjective experience of the timing of their decision and action using a special clock. He found that there was a consistent pattern of brain activity, called the readiness potential, that preceded the conscious decision by about half a second, and the actual movement by about a tenth of a second.

Libet interpreted his results as evidence that free will is an illusion, and that our conscious will is merely an epiphenomenon of the brain's unconscious processes. He wrote, "The initiation of the freely voluntary act appears to begin in the brain unconsciously, well before the person consciously knows he wants to act. Is there, then, any role for conscious will in the performance of a voluntary act?"

Robert Sapolsky is a professor of biology and neurology at Stanford University, who is known for his research on the effects of stress and hormones on animal and human behavior. He has also written extensively on the various factors that influence our choices and actions, such as genes, hormones, neurotransmitters, environment, culture, and history. He has argued that free will is a myth, and that our behavior is determined by a complex web of causes that we are largely unaware of and cannot control. He wrote, "We are nothing more or less than the sum of that which we could not control—our biology, our environments, their interactions." *

* Sapolsky, R. M. (2023). Determined: A science of life without free will. New York, NY: Penguin Press..

More from Dr. R. Sapolsky about hormones:

• Hours to days before that behavior occurred, the hormones in circulation shaped those thoughts , memories , and emotions and altered how sensitive your brain was to particular environmental stimuli. (loc 131)
• Previous minutes, nor by the levels of any hormones marinated his brain in the previous hours to days, not whether he had experienced a life changing event in recent months or years. (loc 316)
• How does testosterone (T) in the preceding minutes to days play a role in determining whether you kill that person? (loc 938)
• The hormone's levels vary manyfold among different individuals, as do levels of receptors for oxytocin in the brain (loc 993)
• Weeks to Years before so hormones can change the brain over the course of minutes to hours. In those cases, "change a brain" isn't some abstraction. (loc.1027)
• The development of the glands that secret those hormones. So on and so on. Each moment follows from all that came. before. (loc 1421)