Neuroecon
A quick summary of Neuroecon
Neural responses to taxation
Distinguishing the "hedonistic" neural responses to 'pure altruism' and 'warm glow' motives.
pure altruism satisfaction from increases in public good. free-riding very common. taxation typical solution
warm glow agency associated with voluntary giving. taxation doesn't produce this. their benefit derives from amount of gift.
ventral striatum and insulae connected to reward processing (money, food, drugs).
but also to charitable giving, deciding to trust others, punishing unfair players
Dictator game You have $100 and decide what to give to charity (different balances of your loss and their game), as well as mandatory taxes
Results
- Larger activation in response to the participant getting money decreases likelihood of giving
- Larger activation in response to *the charity *getting money increases likelihood of giving
Using TMS to disrupt DLPFC and diminish reciprocal fairness
Supplementary material
Ultimatum game is where one proposes a split of e.g. $20, and if refused both players earn $0.
Previous research shows unfair ultimatums are rejected, even if it's a considerable amount of money. Anterior insula and DLPFC activate when responders make the decision of acceptance. Competing theories about whether participants are resisting the temptation to accept (self-interest) or to reject (norm-maintenance). These are both consistent with dual-systems approaches. They think it's not one or the other, but the balancing of the two aims.
Claims in the abstract
- Right (but not left) DLPFC disruption matters
- Participants still judge unfair offers as unfair, despite accepting them
- Implication: DLPFC plays a role in implementation of fairness-related behaviors
Their hypotheses
- Disruption to right DLPFC should be more influential than left, based on previous work on inhibitory control
- Should see a difference between human- and computer- conditions, as norm-enforcing doesn't make sense for computers
The study, logic and procedure
- We don't really know the DLPFC is instrumental in this decision process, or what exactly it's doing if it is (what impulse is it modulating?)
- 52 subjects, no prior TMS experience
- only options are 10, 8, 6, or 4 out of 20.
- each plays 20 times. 10 times with distinct others, 10 times with randomly generated (deciders know)
- repeditive transcranial magnetic stimulation (rTMS) applied for 15 minutes to right or left DLPFC (19/17 subjects) + control condition (16 subjects)
- this brain area will be deactivated for another ~7min after stimulation stops
- fairness assessments took place roughly 4-5 minutes after the 15-minute offline stimulation with rTMS
- DLPFC "very likely" to still be disrupted
Results
- 24% acceptance for human offers of 4
- acceptance of most unfair: 9.3% (sham rTMS), 14.7% (rTMS of left), 44.7% (rTMS of right)
- 37% accepted all unfair offers after rTMS right, none in the other conditions
- rTMS of right same response time 16/4 as 10/10
- given rTMS of right, no effect of offer on probability to accept
- gave questionairres afterwards trying to assess individual differences
- no effect of rTMS on fairness judgments (measured immediately after Ultimatum Game)
- no differences in acceptance of computer-offer conditions across stimulus conditions