Evidence of free will from a tiny worm

For over 3,000 years philosophers and religious thinkers have argued about free will. Some argued that everything has a material cause that determines all material effects including emotions like fear, love, hope and happiness. Others argued that there are also subjective mental states like belief, morality and self-identity that influence individual’s reactions to an objective material stimulus. Now it seems that science has discovered that even worms have free will.

If offered a delicious smell, a roundworm will usually stop its wandering to investigate the source, but sometimes it won’t. Just as with humans, the same stimulus does not always provoke the same response, even from the same individual.

New research at Rockefeller University, published online in Cell, offers a new neurological explanation for this variability, derived by studying a simple three-cell network within the roundworm brain.

“We found that the collective state of the three neurons at the exact moment an odor arrives determines the likelihood that the worm will move toward the smell. So, in essence, what the worm is thinking about at the time determines how it responds,” says study author Cori Bargmann..

“It goes to show that nervous systems aren’t passively waiting for signals from outside, they have their own internal patterns of activity that are as important as any external signal when it comes to generating a behavior.”

The researchers went a step deeper to tease out the dynamics within the network. By changing the activity of the neurons individually and in combination, they could pinpoint each neuron’s role in generating variability in both brain activity and the behavior associated with it.

This is almost impossible to do for humans because the human brain has 86 billion neurons and 100 trillion synapses, or connections, among them.

But the brain of the microscopic roundworm Caenorhabditis elegans, by comparison, has only 302 neurons and 7,000 synapses.

So while the worm’s brain cannot replicate the complexity of the human brain, scientists can use it to address tricky neurological questions that would be nearly impossible to broach in our own brains.

Worms spend their time wandering, looking for decomposing matter to eat. And when they smell it, they usually stop making random turns and travel straight toward the source. This change in behavior is initially triggered by a sensory neuron that perceives the smell and feeds that information to the network the researchers studied.

As the worms pick up the alluring fruity smell of isoamyl alcohol, the neurons in the network transition into a low activity state that allows them to approach the odor. But sometimes the neurons remain highly active, and the worm continues to wander around — even though its sensory neuron has detected the odor.

Scaled up to account for the more nuanced behaviors of humans, the research may suggest ways in which our brains process competing motivations. “For humans, a hungry state might lead to you walk across the street to a delicious smelling restaurant”.

However, if a person finds out that the wonderful smelling food in forbidden by his or her religious or moral commitments it may not be eaten. Thus, a mental state of belief offsets the biological cause and leads to a different behavioral outcome.

There is plenty of evidence suggesting network states have a similar impact on animals with much larger and more complex brains like humans. “In a mammalian nervous system, millions of neurons are active all the time. Traditionally, we think of them as acting individually, but that is changing. Our understanding has evolved toward seeing important functions in terms of collective activity states within the brain.” says Bargmann,

Or as Moses said over 3,200 years ago: “I call heaven and earth to witness against you today, that I have set before you life and death, blessing and curse. Therefore choose life, that you and your offspring may live, (Deuteronomy 30:19)