Irrational Decisions Driven By Emotions
ScienceDaily (Aug. 3, 2006) Irrational behaviour arises as a consequence of
emotional reactions evoked when faced with difficult decisions, according to
new research at UCL (University College London), funded by the Wellcome Trust.
The UCL study suggests that rational behaviour may stem from an ability to
override automatic emotional responses, rather than an absence of emotion per
se.
It has long been assumed in classical theories of economics that people act
entirely rationally when taking decisions. However, it has increasingly become
recognized that humans often act irrationally, as a consequence of biasing
influences. For example, people are strongly and consistently affected by the
way in which a question is presented. An operation that has 40 per cent
probability of success seems more appealing than one that has a 60 per cent
chance of failure.
In the study, published in the journal Science, UCL researchers used a gambling
experiment to establish the cognitive basis for rational decision-making. The
goal of the task was to accumulate as much money as possible, with the
incentive of being paid in real money in proportion to the money won during the
experiment. Participants were given a starting amount of money (£50) at the
beginning of each trial. They were then asked to choose between either a sure
option or a gamble option (where they would have a certain chance of winning
the entire amount, but also of losing it all). Subjects were presented with
these choices under two different frames (i.e. scenarios), in which the sure
option was worded either as the amount to be kept from the starting amount
("keep £20"), or the amount to be deducted ("lose £30"). The two options,
although worded differently, would result in exactly the same outcome, i.e.
that the participant would be left with £20.
The UCL study found that participants were more likely to gamble at the threat
of losing £30 than the offer of keeping £20. On average, when presented with
the "keep" option, participants chose to gamble 43 per cent of the time
compared with 62 per cent for the "lose" option. Furthermore, there was a
marked difference in behaviour between participants. Some people adopted a more
rational approach and gambled more equally and consistently under both frames,
while others showed a real aversion to risk in the "keep" frame while at the
same time displaying high risk-seeking behaviour in the "lose" frame.
Brain imaging revealed that the amygdala, a region thought to control our
emotions and mediate the 'fight or flight' reaction, underpinned this bias in
the decision process. Moreover, the UCL study revealed that people with more
rational behaviour had greater brain activity in the prefrontal cortex, a
region known to be involved in higher-order executive processes, suggesting
that their brains are better able to incorporate their emotions into a more
balanced reasoning process.
Mr Benedetto de Martino, of the UCL Institute of Neurology, says: "It is well
known that human choices are affected by the way in which a question is
phrased. For example, saying an operation carries an 80 per cent survival rate
may trigger a different response compared to saying that an operation has a 20
per cent chance of dying from it, even though they offer exactly the same
degree of risk.
"Our study provides neurobiological evidence that an amygdala-based emotional
system underpins this biasing of human decisions. Moreover, we found that
people are rational, or irrational, to widely differing amounts. Interestingly,
the amygdala was active across all participants, regardless of whether they
behaved rationally or irrationally, suggesting that everyone experiences an
emotional reaction when faced with such choices. However, we found that more
rational individuals had greater activation in their orbitofrontal cortex (a
region of prefrontal cortex) suggesting that rational individuals are able to
better manage or perhaps override their emotional responses."
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