Hi I'm Michael Corayer and this is Psych Exam Review.
In this video we're going to look at the somatic marker hypothesis proposed by Antonio Damasio. So
what is the somatic marker hypothesis? This is a theory for how emotions guide our decision making
and the term somatic refers to our body. So the idea is we have a feeling or an
emotional reaction in our body and that this then marks or indicates to us something about
the options that we're considering. So when I see option A I get a particular feeling
when I see option b i get a different feeling and i actually use those feelings in order to
make a decision. So I'm not using pure reason or rational analysis but I'm actually reliant
on some emotional reactions to the different options in order to be able to make decisions.
Now Damasio became interested in this by studying patients who had damage to their frontal lobes
and this damage seemed to affect their ability to make decisions and this might remind you of the
famous case of Phineas Gage. So Phineas Gage was a railroad worker. In 1848 there was an accident
where an iron rod was propelled through his skull and it took a portion of his left frontal lobe
with it and following his accident gage survived but he had difficulty in regulating his emotions
and he also had difficulties in making sound decisions. Now Damasio looked at patients who
had damage to a particular area of the frontal lobes, this is the ventromedial prefrontal cortex.
That sounds like a lot, so I think it's helpful to understand these brain anatomy terms in order
to get a sense of what we're talking about. If we look at the term ventro or ventral
this actually comes from the Latin for belly and it's the underside because for most animals the
underside would be the belly and the opposite of that would be dorsal and that would be the back.
And you probably know that if you think of a dorsal fin on a shark or a dolphin. So we're
talking about the underside. Then we have medial which refers to middle like the word median and
the opposite of that would be lateral which would be on the sides but here we're talking about the
middle and we're talking about the prefrontal cortex. Prefrontal is before the front so it's
the front most part of the frontal lobes. So now we can see the ventromedial prefrontal
cortex would be the underside middle of the front most part of the frontal lobes. And if we look at
an image here where I've marked the vmPFC we can see it's exactly where we would expect
once we understand the naming system. So back to the somatic marker hypothesis. In looking at
patients who had damage to the vmPFC Damasio saw that they had difficulties and deficits
in their emotional reactivity to certain stimuli and to their ability to make decisions and in his
book "Descartes' Error" he writes about a patient that he refers to as Elliot. Now Elliot had a
tumor in his brain that was surgically removed. It was just above his eye sockets and this meant
that in removing the tumor he did have some damage to his ventral medial prefrontal cortex
and following his surgery Elliot showed reduced emotional reactivity to things that
he said he knew he should have an emotional reaction to but he just wasn't feeling it
and he also struggled to make decisions. He could use rational choice and narrow things down to
a few options but he couldn't seem to decide what was important or what he should focus on.
As a result he wasn't able to keep his job and he struggled with everyday decisions. Damasio also
has described talking with Elliot about scheduling his next appointment and he might ask whether he
prefers Tuesday or Thursday and he said Elliot could endlessly deliberate the pros and cons of
Tuesday versus Thursday. He could go on and on trying to make a rational choice but not being
able to. He wasn't getting a feeling that one of those choices was better than the other and as a
result he couldn't decide. Or as Damasio described this predicament: "to know but not to feel". So
this may make sense when we talk about everyday decisions. You know if you're trying to decide if
you want pizza or tacos there's not necessarily a rational best answer and so it may make sense that
you go with your gut feeling that today pizza feels better, tomorrow maybe tacos will feel
better and that's maybe how my emotional reactions guide my everyday decision-making. But how can we
test this in a more formal lab setting? How can we compare patients with damage to the ventromedial
prefrontal cortex to healthy controls in terms of how they actually make decisions?
So this brings us to the Iowa Gambling Task and this was developed by Antoine Bechara.
The Iowa Gambling Task is a relatively straightforward task. What you do is you
have four piles of cards A B C D and you choose a card from any of the four piles.
And then the card will either give you a gain of money or a loss of money and the purpose of the
task is to draw 100 cards from the different piles and try to maximize how much money you can earn.
Now the trick to the task is that piles A and B are dangerous: they have high rewards but
they have even higher penalties. So over time you'll lose money even though you'll have some
big rewards. Whereas piles C and D are safer. The rewards are lower but the losses are even lower
so over time drawing from C and D you'll gradually accumulate more money.
Of course participants are not told this when they're doing the task. They don't know which
piles are the risky piles and which ones are the safer options. They have to figure it out as they
go and so the question is: How do they figure it out? The somatic marker hypothesis suggests
they figure it out by a feeling in their body. So now we can look at how this Iowa
Gambling Task was used in a study by Bechara with Hannah Damasio, Antonio Damasio, and Gregory Lee.
What they did is they gave the Iowa Gambling Task to patients with vmPFC damage and healthy controls
and while they were doing the task they also measured their skin conductance. This is a measure
of their emotional reactivity. So this measures the sweat in your skin and when you're shown
something that causes some fear or anxiety then we would see a spike in your skin conductance. So
if you were wearing this and I showed you a picture of a snake, you'd probably show
an increase in your skin conductance. Okay, so what did they find in this comparison?
Well, first they found that the healthy controls were better able to switch to piles C and D.
They seem to figure out that A and B just aren't worth the risk
and in the particular version that they did in this study for every 10 cards that you drew from
A or B you'd lose about 250 dollars because you'd gain a thousand but you'd lose 1250.
Whereas in piles C and D you would gain only 500 and then you'd lose only 250 so
overall over the course of 10 cards you'd be up by about 250 dollars if you draw from C and D. And
the healthy controls seem to figure this out over time. They gradually drew more from C and D. Not
only that, their skin conductance showed that they had greater anxiety when it came to piles A and B.
They showed spikes in their skin conductance when they're drawing from those piles.
So the idea is after you've drawn and had some big losses there, you feel this sense of trepidation
in drawing from those piles and the somatic marker hypothesis suggests that it's actually
that feeling that drives you to C and D, rather than some sort of rational analysis. Now how
about the patients with vmPFC damage? Well they didn't show that same spike in skin conductance
and they continued drawing from A and B over the course of the hundred trials. And that
means overall they performed worse on the task. They weren't able to earn as much money because
they kept drawing from those piles that had the big rewards and then you get hit with a loss
that wipes out all those previous gains. But they didn't seem to have that same emotional reaction
to those piles and so without that somatic marker they weren't able to recognize that
piles A and B are a bad choice. And so they kept making the same bad choice over and over again.
Okay, so that's the somatic marker hypothesis
and how it relates to some of this research by Bechara. I hope you found this helpful.
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