As a cognitive scientist, I like the brain. Over the years, the field has learned a lot
from the study of brain damage as well as from brain imaging of normally
functioning brains. For example, the
surgery on the famous patient HM that removed the hippocampus from both sides
of our brain taught us a lot about the influence of that brain structure on our
ability to learn new things as well as the kinds of learning that can be done
without awareness.
Like a number of my colleagues, I have been concerned about
the growing desire to capitalize on our understanding of the brain for
financial gain. Over the past several
years, neuromarketing firms have cropped up that aim to use brain imaging to
help companies do a better job of understanding their consumers. Neural approaches to lie detection aim to
help us get directly at the source of lies to determine who is telling the
truth.
These concerns are laid out in the book Brainwashed: The seductive appeal of
mindless neuroscience by Sally Satel and Scott Lilienfeld. I think these authors make some nice points,
though the book itself is not as effective as it could have been. My concern is that anyone who is not already
well-versed in brain imaging research will have a hard time following the
specifics of the arguments they make.
That said, I think it is worthwhile saying a few words about
why the current advances in neuroscience are not easy to translate into broad
practical applications. There are three
broad problems. First, the technologies
we use to image the brain have limitations that limit their practical
application. Second, our understanding
of psychology limits what we can learn from the brain. Third, our theories of neuroscience are not
advanced enough to create broad practical applications.
Limitations of
Imaging. It is absolutely amazing
that we are able to get a view into what brains are doing while they are doing
it. Using EEG, we can measure electrical
activity that comes through the scalp.
It is hard to know where that activity comes from, but we can measure it
with a high level of precision in time.
Functional MRI examines changes in blood flow to regions of the
brain. This technique allows us to
measure where these changes are happening, though the changes happen over a
period of seconds, which is an eternity in the brain.
Not only do these techniques have limitations in what they
can measure, they are very noisy. That
is, there is a lot of variability in the data, so it takes a lot of
observations in order to separate the valuable signal from all of this
variability.
Practically speaking, then, these brain imaging techniques
are not like an x-ray. If you get
injured, you take one picture (or perhaps a couple), and you can see whether a
bone is broken. With brain imaging, you
may need to take 30 observations or more before you have some sense of what is
happening in a person’s brain.
Think about what this means for using brain imaging to
understand what is happening in a person’s brain. Consider lie detection. What we want to know is whether a person is
lying if we ask them a question (or perhaps 2 or 3). If we have to ask the same question 30 or
more times in order to be able to get a reading, then there is a good chance
that person is adopting some other strategy that is different from what they
would do when answering a question.
This is only one example, but it is important to realize
that the technologies that we use to measure brains limit what we can tell
about individual people from the results of these techniques.
Limitations of
Psychology. The psychologist and
skeptic William Uttal wrote a great book in 2001 called The New Phrenology, in which he
explored limitations in brain imaging techniques. Phrenology is a 19th century
theory that specific regions of the brain are specialized for particular
functions and that the size of those regions determined people’s behavior. The phrenologists used bumps on the head as a
brain imaging technique. The larger the
bumps, the larger the region of the brain beneath.
As Uttal points out, the problem with phrenology was not so
much the assumption that the brain has regions that are specialized for
different functions. The brain does have
distinct circuits in it. One big problem
with phrenology was the labels. The
phrenologists would like for brain areas that were associated with high-level
concepts like gratitude or caution.
Based on our modern view of psychology, those labels seem quaint.
But, modern psychology has not completely cracked the code
for behavior either. We use terms like
attention, memory, and even lying, but these behaviors all reflect many
different psychological processes. Hal
Pashler’s classic book on attention,
for example, makes clear that the term attention refers to many different
things, and that we are just beginning to understand all of them.
Until we have a well worked-out theory of the psychology of
areas like consumer behavior and lying, it will not be possible to develop
brain imaging techniques that will give insight into specific aspects of
people’s behavior. The reason is that
there is a temptation to look for a single neural signature related to
particular aspects of behavior, even though a particular behavior may arise
from many different underlying sources.
In their book, Satel and Lilienfeld point out that there are many
different things someone might be doing when they are lying, so there is no
reason to believe that all of them would lead to a clear pattern of brain
activity.
Limitations of neuroscience. A final hurdle to using neuroscience in
practical applications is limitations in our understanding of what the brain is
doing. Obviously, neuroscience is a
young field, and there is still a lot for us to learn. But, there are still some fundamental
questions that remain to be answered.
One key question surrounds the organization of the brain
across different people for high-level thinking. We know from studies of humans and other
animals that there is a fair amount of similarity in the organization of the
brain across individuals for functions like vision and hearing. That makes sense. We all grow up in a similar visual
environment, for example. The physics of
light have not changed in billions of years, and so neural systems have been
able to adapt to the way light bounces off surfaces on earth.
When it comes to high-level reasoning, though, it is much
less clear that different people’s brains have to act in the same way. Even though we all form similar categories,
we have very different experiences to create those categories. We all learn similar reasoning skills through
our years of education, but that does not mean that every person’s brain
organized itself in the same way to serve those functions. Until we resolve that question, it is hard to
know how well we will be able to predict people’s behavior from what their
brains are doing.
All this is to say that it is worth having a healthy
skepticism for anyone who wants to sell you something that purports to predict
what people are doing from some measure of their brains. That said, the next decades are going to
reveal a lot more about brain and behavior.
It is a great time to be in the field.
