Friday, January 26, 2007

Gambling Made Easy

Wow, another study in The Annals of the Incrediby Obvious has appeared in Science. Why do I think it's time for me to give up and go home, you ask??
People More Cautious Than Reckless When Gambling

. . .

The study, detailed in the Jan. 26 issue of the journal Science, also revealed that people respond more strongly to potential losses than potential gains. Thinking about the possibility of winning money turns on some of the same areas of the brain that are activated when people take cocaine, eat chocolate or look at a beautiful face, explained study team member Russell Poldrack.

These "reward centers" of the brain that get turned on when we think about winning money get turned off when we think about losing money. [NOTE: No! You don't say!!]

"You turn down the reward areas of the brain, and you turn them down more strongly for losses than you turn them up for gains," Poldrack said.

. . .

Tom SM, Fox CR, Trepel C, Poldrack RA. The Neural Basis of Loss Aversion in Decision-Making Under Risk. Science 315: 515-518.

People typically exhibit greater sensitivity to losses than to equivalent gains when making decisions. We investigated neural correlates of loss aversion while individuals decided whether to accept or reject gambles that offered a 50/50 chance of gaining or losing money. A broad set of areas (including midbrain dopaminergic regions and their targets) showed increasing activity as potential gains increased. Potential losses were represented by decreasing activity in several of these same gain-sensitive areas. Finally, individual differences in behavioral loss aversion were predicted by a measure of neural loss aversion in several regions, including the ventral striatum and prefrontal cortex.


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At January 28, 2007 11:53 AM, Anonymous Anonymous said...

Hey Neurocritic--I think you miss the point of the Tom et al. study that just appeared in _Science_.

First: It is actually not so obvious that potential losses would "turn down" responses in the reward centers when people make decisions. Several top researchers had speculated that potential losses would be associated with negative emotional responses as mediated by activity in, say, the anterior insula or amygdala. Second, it is not so obvious that the abstract representation of value when making decisions would involve the same reward circuitry that responds to anticipated or experienced reward. Third, the fact that the reward circuitry is substantially more responsive to potential losses than equivalent gains is not so obvious--it is difficult to reconcile with rational choice models but supports prospect theory, the leading behavioral model of decision under uncertainty for which Daniel Kahneman won the 2002 Nobel Memorial Prize in Economic Sciences. Fourth, the finding that individual differences in sensitivity in this particular circuitry are very highly correlated with individual differences in risk attitudes is exciting and also supports the prospect theory interpretation of risk aversion for mixed (gain/loss) gambles. Fifth, the ancillary finding of a positive correlation between gain and loss sensitivity is rather surprising. Sixth, mapping out the relationship between the dopaminergic circuitry and risk-taking behavior is a first step that may eventually lead to better understanding and treatment for compulsive gambling behavior--for instance, as often exhibited by Parkinsons patients after they begin a regimen of dopamine agonist medication.

It is easy to make fun of a study after reading only a headline. But with all due respect I find your critique naive and superficial.


At January 28, 2007 1:48 PM, Blogger The Neurocritic said...

Sorry, CF, my reward circuitry was turned way down. I did read the paper, but looming deadlines prevented me from writing a full critique. Apologies for that. I'm usually quite thorough.

A few questions and comments for you, if I may:

(1a) Many other studies have indicated that potential losses are associated with negative emotional responses. So the difference here is that the participants never knew the results of their decisions in the Tom et al. study, i.e., there were no consequences during scanning. If there are no immediate consequences, doesn't that change one's response?

McClure SM, Laibson DI, Loewenstein G, Cohen JD. Separate neural systems value immediate and delayed monetary rewards. Science. 2004 Oct 15;306(5695):503-7.

Relevant here??

(1b) There were 3 runs, and subjects were told that only one gamble from each of these runs would be played; i.e., there were only 3 "real" gambles for the entire experiment (albeit which ones was unknown).

(1c) Supplement, page 3: In order to encourage participants to reflect on the subjective attractiveness of each gamble rather than revert to a fixed decision rule (e.g., accept only if gain ≥ 2 × loss), we asked them to indicate one of four responses to each gamble (strongly accept, weakly accept, weakly reject, and strongly reject) using a four-button response box. We also
instructed them to respond as quickly as possible within the 3-second trial duration.

People typically aren't rushed into making 256 decisions in 12.8 minutes (a total of 24.7 minutes including the interstimulus intervals). I fail to see how this experimental design relates to making momentous life decisions (see point #7 below regarding press coverage). Or to compulsive gambling behavior, for that matter, since win/loss results aren't withheld until the end of the session in Vegas.

(2) ...not so obvious that the abstract representation of value when making decisions would involve the same reward circuitry that responds to anticipated or experienced reward.

Yes? No?

Nieuwenhuis S, Heslenfeld DJ, von Geusau NJ, Mars RB, Holroyd CB, Yeung N. Activity in human reward-sensitive brain areas is strongly context dependent. Neuroimage. 2005 May 1;25(4):1302-9.

(3) I don't know anything about prospect theory versus rational choice models, but I thought Kahneman (and neuroeconomists, e.g., Sanfey et al., 2006 TICS) had already tipped the scales way in favor of the former.

(4) Many of the correlations with individual differences in risk aversion are, indeed, interesting. A question about the one of the puzzling relationships:

For increasing gains, we observed a significant correlation with behavioral loss aversion in the sensorimotor cortex and superior frontal cortex (fig. S4).

What is the significance of this result? Why sensorimotor cortex??

(5) Page 4: the ancillary finding of a positive correlation between gain and loss sensitivity is rather surprising. OK, I'll take your word for it.

(6) I'm not a funding agency, you don't have to justify the broader impacts ("future patients may benefit...").

(7) It wasn't only the headlines that prompted my admittedly snarky post, it was some of the quotes in the article, e.g., extrapolations to scenarios such as leaving a bad marriage, taking cocaine, eating chocolate, and looking at a beautiful face.

Thanks for taking the time to comment on the paper.


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