Friday, August 17, 2012

Eddy Nahmias - Does Contemporary Neuroscience Support or Challenge the Reality of Free Will?

One of the foundational pieces of research in support of a neuroscientific argument against free will has been questioned, and the new interpretation opens up the debate once again. The original research goes back to the early 1980s - here is a brief explanation of the study and the findings, from New Scientist:
In the early 1980s, Benjamin Libet at the University of California in San Francisco, used electroencephalography (EEG) to record the brain activity of volunteers who had been told to make a spontaneous movement. With the help of a precise timer that the volunteers were asked to read at the moment they became aware of the urge to act, Libet found there was a 200 millisecond delay, on average, between this urge and the movement itself.

But the EEG recordings also revealed a signal that appeared in the brain even earlier – 550 milliseconds, on average – before the action. Called the readiness potential, this has been interpreted as a blow to free will, as it suggests that the brain prepares to act well before we are conscious of the urge to move.

This conclusion assumes that the readiness potential is the signature of the brain planning and preparing to move. "Even people who have been critical of Libet's work, by and large, haven't challenged that assumption," says Aaron Schurger of the National Institute of Health and Medical Research in Saclay, France.
In 2009, Judy Trevena and Jeff Miller of the University of Otago in Dunedin, New Zealand, ran an experiment to challenge the findings. They showed that the brain begins to assemble neurons for possible responses and that once one hits a specific threshold, a decision has been made to act. In their experiment, those subjects who reacted quickest to the prompt had the largest neuron buildup. 

It seemed that their findings supported the Libet findings. However, Aaron Schurger of the National Institute of Health and Medical Research in Saclay, France, challenges that conclusion, largely based on the fact that subjects showed readiness potential (RP) before making a decision to move but, importantly, the RP was the same whether or not they chose to move.

Miller concluded that the RP may simply show that the brain is paying attention and not be indicative that the brain has made a decision to act. Likewise, Shurger said of the results: "...what looks like a pre-conscious decision process may not in fact reflect a decision at all. It only looks that way because of the nature of spontaneous brain activity."

Again, from New Scientist:
So what does this say about free will? "If we are correct, then the Libet experiment does not count as evidence against the possibility of conscious will," says Schurger.

Cognitive neuroscientist Anil Seth of the University of Sussex in Brighton, UK, is impressed by the work, but also circumspect about what it says about free will. "It's a more satisfying mechanistic explanation of the readiness potential. But it doesn't bounce conscious free will suddenly back into the picture," he says. "Showing that one aspect of the Libet experiment can be open to interpretation does not mean that all arguments against conscious free will need to be ejected."

According to Seth, when the volunteers in Libet's experiment said they felt an urge to act, that urge is an experience, similar to an experience of smell or taste. The new model is "opening the door towards a richer understanding of the neural basis of the conscious experience of volition", he says.
That is some current background for this article from Big Questions Online - a look at neuroscience and free from Eddy Nahmias. He makes reference to the Libet study and the fact that the outcomes were only slightly above chance in the first place, but this newer research came out (I think) after the article was written.

Does Contemporary Neuroscience Support or Challenge the Reality of Free Will?

Does Contemporary Neuroscience Support or Challenge the Reality of Free Will?

August 13, 2012 
All the world’s a stage, and all the men and women merely players.— Shakespeare

 Humans love stories.  We tell each other the stories of our lives, in which we are not merely players reading a script but also the authors.  As authors we make choices that influence the plot and the other players on the stage.  Free will can be understood as our capacities both to make choices—to write our own stories—and to carry them out on the world’s stage—to control our actions in light of our choices.

What would it mean to lack free will?  It might mean we are merely puppets, our strings pulled by forces beyond our awareness and beyond our control.  It might mean we are players who merely act out a script we do not author.  Or perhaps we think we make up our stories, but in fact we do so only after we’ve already acted them out.  The central image in each case is that we merely observe what happens, rather than making a difference to what happens.

How might neuroscience fit into the story I am telling?  Most scientists who discuss free will say the story has an unhappy ending—that neuroscience shows free will to be an illusion.  I call these scientists “willusionists.” (Willusionists include Sam Harris, Jerry Coyne, Jonathan Bargh, Daniel Wegner, John Dylan Haynes, and as suggested briefly in some of their work, Stephen Hawking and Richard Dawkins.) Willusionists say that neuroscience demonstrates that we are not the authors of our own stories but more like puppets whose actions are determined by brain events beyond our control.  In his new book Free Will, Sam Harris says, “This [neuroscientific] understanding reveals you to be a biochemical puppet.” Jerry Coyne asserts in a USAToday column: “The ineluctable scientific conclusion is that although we feel that we’re characters in the play of our lives, rewriting our parts as we go along, in reality we’re puppets performing scripted parts written by the laws of physics.”

There are several ways willusionists reach their conclusion that we lack free will.  The first begins by defining free will in a dubious way.  Most willusionists’ assume that, by definition, free will requires a supernatural power of non-physical minds or souls:  it’s only possible if we are somehow offstage, beyond the causal interactions of the natural world, yet also somehow able to pull the strings of our bodies nonetheless.(For example, Read Montague.)  It’s a mysterious picture, and one that willusionists simply assert is the ordinary understanding of free will.  Based on this definition of free will, they then conclude that neuroscience challenges free will, since it replaces a non-physical mind or soul with a physical brain. 

But there is no reason to define free will as requiring this dualist picture.  Among philosophers, very few develop theories of free will that conflict with a naturalistic understanding of the mind—free will requires choice and control, and for some philosophers, indeterminism, but it does not require dualism.  Furthermore, studies on ordinary people’s understanding of free will show that, while many people believe we have souls, most do not believe that free will requires a non-physical soul.  And when presented scenarios about persons whose decisions are fully caused by earlier events, or even fully predictable by brain events, most people respond that they still have free will and are morally responsible.   These studies strongly suggest that what people primarily associate with free will and moral responsibility is the capacity to make conscious decisions and to control one’s actions in light of such decisions.

But willusionists also argue that neuroscience challenges free will by challenging this role for consciousness in decision-making and action.  Research by Benjamin Libet, and more recently by neuroscientists such as John Dylan Haynes, suggests that activity in the brain regularly precedes behavior—no surprise there!—but also precedes our conscious awareness of making a decision to move.  For instance, in one study neural activity measured by fMRI provided information about which of two buttons people would push up to 7-10 seconds before they were aware of deciding which to push.

If such early brain activity always completely determines what we do before our conscious thinking ever comes into the picture, then this would suggest we lack free will, because our conscious thinking would happen too late to influence what we did—an audience rather than author.  But the data does not show that brain activity occurring prior to awareness completely causes all of our decisions.  In the study just described, the early brain activity correlates with behavior at only 10% above chance.  It is not surprising that our brains prepare for action ahead of time and that this provides some information about what people will do. 

Of course, improved brain imaging technology will likely provide increasingly precise predictions of future behavior.  But here’s my prediction:  the more complex the decisions and behavior, the more likely such predictions will be based on information about the very neural processes that are the basis of conscious deliberation and decision-making.

Related Questions 
Once we assume that all mental processes have neural correlates, then whether consciousness plays a role in our complex behavior turns on whether the neural correlates of conscious processes occur at the right time and place to influence behavior.  It’s unlikely that the neural processes involved in complex deliberations, planning, and self-control play no role in behavior.  Instead, there is evidence that conscious and rational thinking can play an important causal role in complex behavior.  If we give up the mysterious picture of our conscious selves being offstage, then we can give up the threatening image of our brains pulling the strings while we helplessly watch.    

One reason it is easy to move from the assumption that neural processes cause behavior to the presumption that consciousness does nothing is that neuroscience still lacks a theory to explain how certain types of brain processes are the basis of conscious or rational mental processes.  Without such a story in place, it is easy to assume that neuroscientific explanations supersede and bypass explanations in terms of conscious and rational processes.  But that conclusion is unwarranted.  Explanations in organic chemistry do not explain away life; they explain life.  A more complete scientific theory of the mind will have to explain how consciousness and rationality work, rather than explaining them away.  As it does, we will come to understand how and when we have the capacities for conscious and rational choice, and for self-control, that people ordinarily associate with free will.  These are the capacities to reflect on our desires and reasons, to consider which of them we want to motivate us, and to make efforts to act accordingly—or as Roy Baumeister explained in his recent post, to habituate ourselves to make choices that accord with our reflectively endorsed goals.

By understanding how the most complex thing in the universe—the human brain—works, we can better understand our capacities to make choices and to control our actions accordingly.  On this telling of the tale, neuroscience can help to explain how free will works rather than explaining it away.

Now, if one insists that free will requires that we have an impossible ability to make choices beyond the influence of anything, including our own brains—or to make choices for no reason at all—then you will be disappointed by the story I am telling.  Here, willusionists like Sam Harris and I agree that we cannot have what is impossible.  Our choices do not arise from nothing any more than an author’s stories arise from nothing, but our choices do influence the way our stories unfold.

Nonetheless, fascinating research suggests that our conscious reasoning and planning is not pulling the strings as much as we tend to believe.  We are subject to biases and influences beyond our awareness, and we sometimes confabulate or rationalize our behavior. But our stories are not always fiction.  Other research suggests that our deliberations and decisions can have significant causal influences on what we decide and do, especially when we have difficult decisions to make and when we make complex plans for future action.

Free will is not all-or-nothing.  It involves capacities that we develop as we mature, but that have limitations.  Recognizing that people have differing degrees of free will can help us better determine when, and to what extent, people are responsible for their actions, and are deserving of praise or blame.  Indeed, where it really matters—legal responsibility—it is most useful to understand free will as a set of capacities for reasoning and self-control which people possess to varying degrees and have varying opportunities to exercise.

In this respect, neuroscience and other sciences of the mind can play an important role by providing new insights into our capacities for rationality and self-control, as well as their limitations.  We do not write our stories from scratch, but within the context of a complicated world of influences and interactions, our tales are not “full of sound and fury, signifying nothing.”

Questions for the discussion:
  • What do you think free will is?
  • Do you think free will is all-or-nothing or that we possess and exercise free will to varying degrees?  How much free will do we have?
  • Is free will necessary to deserve praise and blame for one’s actions?  If so, how much are people responsible for their actions and their situations?
  • Is free will inconsistent with a naturalistic worldview—with an understanding of our conscious minds as physically instantiated in our brains?
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