PSYC 4750 Lecture Notes - Lecture 16: Iowa Gambling Task, Somatic Marker Hypothesis, Phineas Gage
17 May 2018
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03/29/2018 Lecture 16: Choice – Risk and Reward
Phineas Gage
• Rod shot through his brain, changing his personality
• Provided evidence for brain-basis of personality
o Involving the pre-frontal cortex
• Likely experienced a loss of behavioural inhibition
A Modern Case: EVR
• Underwent surgery to remove tumour from orbital frontal cortex
• After surgery, he still had the same level of intelligence, could form and maintain memories and
had no psychiatric symptoms
• But ended up losing his job and getting a divorce
o Likely due to impulsivity
• In social situations his decision making was impaired
o Impaired connectivity between orbital frontal cortex and limbic areas of the brain like
the amygdala
What is a Decision?
• More than one response option
• Options vary in terms of:
o Size of gain or loss
o Probability of gain or loss
o Delay to receiving that gain or loss
o Risk vs. ambiguity
Iowa Gambling Task
• 4 cards – each has a chance of winning and losing
• 2 cards are extra risky, 2 are extra safe
• Most of us learn over time that it is better to go with the safer cards
• Normal patients vs. brain damaged patients (similar to EVR – orbitofrontal cases)
o Normal patients prefer the good decks
o Brain damaged patients prefer the bad decks
• Somatic marker hypothesis – during decision-making we re-activate memories about the
decision options based on our past experiences
o These memories include the emotional states, which are re-activated at a physiological
level (the somatic markers)
o Options that are positively tagged are favoured, options that are negatively tagged are
avoided
o This tagging mechanism can speed up a slow cost-benefit analysis
Skin Conductance Responses
• Measures sweating from fingertips (index of sympathetic nervous system)
• Has been used in the Iowa gambling task
o Measured SCR during the task
• People with Orbital frontal cortex (OFC) damage reacted the same to picking risky vs. safe cards
• Normal controls show a SCR when picking a risky card
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