Inter-Cultural Differences, Behaviour, and Brain Activity — do their brains work differently from yours?

Have you ever caught yourself thinking “they’re just wired differently,” when thinking about people from other cultures? If you’re from the first world, that thought is most likely accompanied by feelings of tremendous guilt (you know, because that’s clearly racist), followed by some form of redemption behaviour, like calling up your inter-culturally diverse friends to see if they want to hang out and do things from their cultures that are totally different from yours. You know, because you’re clearly not racist, right?

Racial stereotypes often highlight behavioural differences as lines of ethical, cultural, and social demarcation. The truth is, people may actually be wired differently, in that brain activity amongst some cultures may differ from that of others in response to nearly identical stimuli.

In 2012, the March edition of a Neuroeconomic Journal called Philosophical Transactions B published a study highlighting a relationship between delay discounting (your tendency to undervalue a large reward that will come to you later, versus a clearly smaller reward available to you sooner, or immediately), a person’s culture of origin, and their brain activity whilst making choices.

During the early days of cross-cultural decision making research, Gallimore et al (1974) demonstrated that the ability to delay gratification (get a larger reward later versus a smaller reward, sooner) was directly related to participant culture of origin. They collected 202 Hawaiian and 49 Japanese-American adolescents and asked them to indicate what they would do with USD 1,500. Their evidence showed that Hawaiians were more likely to describe immediate consumption than the Japanese, noting that they strictly controlled for obvious alternate explanations like socioeconomic status.

Far more recently, Kim, Shin Sung, McClure (2012) & investigated cultural differences in delay discounting by contrasting behaviour and brain activity in Western (American) and Eastern (Korean) subjects. They collected students from top universities in America and Korea (mean participant age = 22), and required them to make a series of choices between smaller, sooner rewards larger, later rewards.

Throughout all tasks, participant brain activity was measured using fMRI (Magnetic Resonance Imaging). Note that fMRI does not allow for a clear understanding of exactly what the brain is doing, but rather simply shows that the brain is using some of its parts more than others.

The entire brain is scanned, and amount of brain activity is inferred through the identification of areas where the blood is most oxygenated; the idea being that the areas of the brain where the blood is the most oxygenated must be the most active.

In the Kim et al experiments, each choice trial was followed by a 12 second inter-trial interval to allow blood oxygenation levels to return to baseline. In essence, they wanted to see if blood oxygination levels increased when stimuli were present, and then wanted to allow blood levels to return to normal when they were absent, so they could show that there was a clear relationship between brain activity, and the requirement for subjects to make a choice.

Not only did Kim et al find that Korean participants discounted the value of future rewards notably less than their American colleagues (ie, Koreans were more likely to pick the larger reward later than the Americans), they furthermore discovered that Koreans showed significantly lower activity in the Ventral Striatum (VStr) than Americans every time they were presented with potential for immediate reward. For the neuronewbie, the VStr is the bottom part of the striatum (featured in red — see figure), and is one of a number of brain areas associated with reward processing and emotional reactivity.

Although this sounds pretty intense on its own, think of it in the context of what we know already about VStr activity and learning. Schultz, Dayan, & Montague (1997) explored the impact of manipulating dopamine release on a subject’s ability to learn. They found that learning is driven by changes in the expectations about future events, and physiologically confirmed with dopamine.

Through optogenetics (a process whereby animals have an electronic receiver surgically attached to their brain, and it is subsequently used to manipulate the effects of substances that are injected/injested), Schultz et al experimented with blocking the release of dopamine, as well as manually releasing it and were able to replicate the learning process; this manual release and blocking of dopamine in a controlled environment supported their theory that when subjects predict one outcome, and another occurs, dopamine is released to reinforce the fact that something happened that the subject should remember.

Scientists modify subjects to manipulate dopamine activity in controlled experiments, but is it possible that the same effect is evident in the absence of deliberate mutation? Did your parents condition you to learn more slowly or quickly, pick a smaller/sooner option over a larger/later option, through the methods they applied to condition your responses to the universe, and, moreover, does this mean that dopamine release blocking can be triggered through conditioning?

I think it would be interesting to observe the experiments Schultz et al performed on optogenetically manipulated rats with human subjects from western and eastern cultures, to explore whether the results were replicable without mutation.

Furthermore, I think it would be neat to continue exploring the impact of controlled dopamine release to deliberately prevent, or falsely replicate the learning experience amidst human participants from different cultures, exploring which cultures require the most (or the least) dopamine to reinforce new lessons.

If you could change someone’s behaviour by controlling dopamine release in their brain, what would you make them do?

References —

Gallimore, R, Weiss, Leslie B., Finney, R. (1974) Cultural differences in delay of gratification: A problem of behavior classification. Journal of Personality and Social Psychology, Vol 30(1), Jul 1974, 72–80.

Kim, B., Shin Sung, Y., & McClure, S.M., (2012). The Neural Basis of Cultural Differences in Delay Discounting DOI: 10.1098/rstb.2011.0292, 23 January 2012.

Schultz, W., Dayan, P., & Montague, P. R. (1997). A neural substrate of prediction and reward. Science, 275, 1593–1599.

Ubeda-Bañon I, Novejarque A, Mohedano-Moriano A, et al. (2007). Projections from the posterolateral olfactory amygdala to the ventral striatum: neural basis for reinforcing properties of chemical stimuli. BMC Neuroscience 8: 103.

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