Teen brain wired to take risks

Teenagers do crazy things, and the chemistry of their brains might explain why, say researchers.

The adolescent brain is extra sensitive to reward signals when pay-off for a risk is higher than expected, say cognitive neuroscientist Dr Russell Poldrack, from the University of Texas, Austin and colleagues.

They say the discovery might help explain why teens take risks that don’t seem worth it to adults – from driving too fast to experimenting with drugs.

“Teenagers seek out these sorts of rewarding experiences, and this provides a little explanation for that,” says Poldrack, whose research is published in this week’s Nature Neurosciece.

“In the long run, it may help us understand how addictions start and develop.”

Prediction error

To zero in on the neuroscience behind risk-taking behaviour in adolescents, Poldrack and colleagues focused on a concept called prediction error, which describes the difference between what a person expects to happen and what actually happens.

If you anticipate a rich sip of full-bodied espresso, for example, but you end up gulping weak, watery, and burnt coffee, that’s a negative prediction error.

If you expect nothing from a friend for your birthday but he gives you $20, that’s a positive error – far better than expected.

To test the brain’s reaction to positive prediction errors at different stages of life, the scientists enlisted 45 people, ranging in age from 8 to 30.

Each participant was shown a series of abstract kaleidoscopic images and challenged to categorise the figures as logos belonging to one of two fictional colleges.

When they got an answer right, participants earned a small amount of money and they all gradually learned which logos went with which colleges and which ones were worth more than others.

There were a few twists, though: Sometimes, an answer that should’ve been correct was judged as wrong.

Sometimes, a wrong answer was rewarded as a correct one. And sometimes, the reward was larger or smaller than the exercise indicated it should be.

With a mathematical model, the researchers were able to determine how much money each person expected to get with each answer and compare that with what they actually received. At the same time, fMRI’s showed what was happening in the brain.

Dopamine release

Previous research has shown a surge of activity in a brain region called the ventral striatum when reality exceeds a person’s expectations.

In the new study, the region’s response was highest in participants between 14 and 19 years old when they received more money than anticipated.

Brain activity in the ventral striatum is related to the release of dopamine, a nerve-signalling molecule that helps the brain process rewards and can be involved in addictions.

With more dopamine flowing, a teenager is likely to feel that a risky behaviour – when it ends well – is so much more rewarding than it might seem to a child or adult.

So, for example, the social rewards of staying out past curfew might outweigh the likelihood of getting in trouble for an adolescent.

And the physical pleasure of getting drunk might outweigh the dangers, including the next day’s hangover.

Besides providing insight into how addictions might begin in adolescence, the new study might help parents channel their teens into more positive risk-taking activities, like playing sports or acting in school plays, suggests Dr Adriana Galvan, a developmental cognitive neuroscientist at the University of California, Los Angeles.

“Adolescents are uniquely sensitive to the uncertainty in the world,” says Galvan. “Perhaps their willingness to engage in uncertainty is driven by the potential rewards that might result from that uncertainty. For them, the rewards loom so much bigger than the potential negatives.”

Reference Link
http://www.abc.net.au/science/articles/2010/05/18/2902619.htm?site=science&topic=latest

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ABC

Washing hands makes tough choices easier

Washing hands with soap and water

Washing our hands after making a decision is both literally and figuratively cleansing, according to a new study, suggesting that sensory experiences often reflect abstract feelings.

Scientists report that when people wash their hands immediately after making a decision, they are less likely to rationalise its merits – possibly making them less content with the decision but more objective about the option they rejected.

“There is a really clear psychological connection between feeling morally clean and physically clean, and between feeling morally dirty and physically dirty,” says Spike Lee, a doctoral student in social psychology at the University of Michigan, Ann Arbor. His new study appears today in the journal Science.

“Now, we’re expanding the scope of the metaphor to mean wiping the slate clean,” he says. “We’re saying that things in the past can be washed away and you can start something afresh. I think this might have pervasive implications about how we live our daily lives.”

The English language is full of metaphors that are starting to pan out in science. For example, people actually feel physically colder when given a cold shoulder or an icy stare, says Katie Liljenquist, a social psychologist at Brigham Young University , Utah.

The concept of moral cleansing through physical washing spans centuries, religions and works of literature – from ritual baptisms to Lady Macbeth’s attempts to wash away the guilt of murder with some water and the cry: “Out, damned spot!”

Sense of control

In her work, Liljenquist has found that being in a clean environment makes people more likely to behave ethically and generously. Her studies also show that using an antiseptic wipe absolves people of some moral guilt and that the simple act of cleaning gives people a sense of control, liberation and clarity of mind.

Lee wondered how washing might affect other brain processes, including the concept of cognitive dissonance, in which we make ourselves feel better by focusing on the positives of our selected choices and dwelling on the negatives of our rejected ones.

In one experiment, which was disguised as a consumer survey, 40 college students made a top-10 list of CDs and were then allowed to choose between their fifth and sixth-ranked choices and keep the one they chose. Immediately, they were given a task that had them evaluate soap by either looking at it or washing their hands with it. Finally, they re-ranked the CDs.

The typical pattern in a scenario like this is for people to rank their selected choice higher in the second round and their rejected choice lower. The behaviour is a sign that they’ve rationalised their choice to themselves, and students who only looked at soap followed the trend.

Those who had scrubbed their hands, however, re-ranked the CDs in the same positions as they had the first time around. A second experiment with fruit jams showed the same pattern.

More rational behaviour?

In essence, Lee proposes, washing your hands is like wiping your brain’s slate clean from residual psychological processes, including the act of justifying decisions. While the cleansing act might leave you less satisfied with your ultimate choice, it could make you a more rational decision-maker and more willing to recognize the negative consequences of your decision.

Instead of blindly loving the car you bought or the vacation you chose to go on, for example, you might notice your choice’s flaws and use the experience to pick something different next time.

The study doesn’t offer any immediate advice for how to incorporate hand washing into the decision-making process or whether casually offered antiseptic wipes might help you convince your spouse to do what you want. Instead, it offers insights into the complexities of our minds.

It also suggests that schools, workplaces, even cities might elicit better behaviour by encouraging cleanliness.

“This is just one single study, but I think it has potential implications for broader psychological liberation,” Liljenquist says.

“If people are experiencing a mental clean slate when they engage in physical cleaning, it’s possible that a physically clean environment could make them more prepared to learn and digest new information.”

Reference Link
http://www.abc.net.au/science/articles/2010/05/07/2893401.htm?site=science&topic=latest

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ABC