Decisons Appear Preconsciously In The Brain

Unconscious decisions in the brain
A team of scientists has unravelled how the brain unconsciously prepares our decisions

Source: Press-Information Bernstein Centers for Computational Neuroscience/13.04.2008

Already
several seconds before we consciously make a decision ist outcome can
be predicted from unconscious activity in the brain. This is shown by a
study of scientists from the Max Planck Institute for Human Cognitive
and Brain Sciences in Leipzig, in collaboration with the Charité
University Hospital and the Bernstein Center for Computational
Neuroscience in Berlin.

The researchers from the group of Professor John-Dylan Haynes used
a brain scanner to investigate what happens in the human brain just
before a decision is made. "Many processes in the brain occur
automatically and without involvement of our consciousness.

This prevents our mind from being overloaded by simple routine tasks.
But when it comes to decisions we tend to assume they are made by our
conscious mind. This is questioned by our current findings."

The study by Haynes and his colleagues Chun Siong Soon, Marcel Brass
and Hans-Jochen Heinze will be published in the May issue of Nature
Neuroscience and will available online on Sunday April 13th at 1pm EST
(Embargo date).

In the study participants could freely decide
if they wanted to press a button with their left or right hand. They
were free to make this decision whenever they wanted, but had to
remember at which time they felt they had made up their mind. The aim
of the experiment was to find out what happens in the brain in the
period just before person felt the decision was made. The researchers
found that it was possible to predict from brain signals which option
participants would take already seven seconds before they consciously
made their decision.

Normally researchers look what happens
when the decision is made, but not what happens several seconds before.
The fact that decisions can be predicted so long before they are made
is a striking finding.

This unprecedented prediction of a free
decision was made possible by sophisticated computer programs that were
trained to recognize typical brain activity patterns preceding each of
the two choices. Micropatterns of activity in frontopolar cortex were
predictive of the choices even before participants knew which option
they were going to choose.

The decision could not be
predicted perfectly, but prediction was clearly above chance. This
suggests that the decision is unconsciously prepared ahead of time but
the final decision might still be reversible.

"Most
researchers investigate what happens when people have to decide
immediately, typically as a rapid response to an event in our
environment. Here we were focusing on the more interesting decisions
that are made in a more natural, self-paced manner", Haynes explains.

More than 20 years ago the American brain scientist Benjamin Libet
found a brain signal, the so-called "readiness-potential" that occurred
a fraction of a second before a conscious decision. Libet's experiments
were highly controversial and sparked a huge debate.

Many
scientists argued that if our decisions are prepared unconsciously by
the brain, then our feeling of "free will" must be an illusion. In this
view it is the brain that makes the decision, not a person's conscious
mind. Libet's experiments were particularly controversial because he
found only a brief time delay between brain activity and the conscious
decision.

In contrast, Haynes and colleagues now show that
brain activity predicts even up to 7 seconds ahead of time how a person
is going to decide. But they also warn that the study does not finally
rule out free will: "Our study shows that decisions are unconsciously
prepared much longer than previously thought.

But we do not
know yet where the final decision is made. Especially we still need to
investigate whether a decision prepared by these brain areas can still
be reversed."

Original publication:
Chun Siong Soon, Marcel Brass, Hans-Jochen Heinze & John-Dylan Haynes
(2008): Unconscious determinants of free decisions in the human brain:
Nature Neuroscience May 2008.

F Prof. Dr. John-Dylan Haynes/E-Mail: haynes(at)bccn-berlin.de