Scientific Advances
Natural compound speeds bone growth
Astronomers spy massive stars in the making
Frog gene map a leap forward for humans
Sun-shy mums may raise MS risk in babies
Soft fossils provide new target for ET search
Mammoth blood brought back to life
Outdoor exercise can boost self esteem
Athletes on growth hormone 'sprint faster'
Countdown begins to 520 day 'Mars mission'
Warmer planet to stress humans: study
Plasma rocket to shorten space voyages
Vaccine may trigger infant epilepsy onset
'Fingerprinting' points to dusty Australia
The hole in the ozone layer: 25 years on
Humans interbred with Neanderthals: analysis
Herschel shows star formation is slowing
Washing hands makes tough choices easier
'Face-book' to measure pain in mice
Science gives clues to World Cup success
Human sigh acts as a reset button
Expert confirms Phar Lap arsenic theory
Dictionary blunder a matter of gravity
Warning on high-dose vitamin D
Calling mum makes you feel better
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."

Climate change impact on malaria questioned
Single lens glasses can help prevent falls
Movies manipulate our primal response
Luminescent sharks become invisible
Synthetic biology research gets a hearing
Source of ancient carbon 'burp' detected
Why the goddess of love is in a spin
Computer program recognises online sarcasm
New dinosaur had record-sized horns
Physicists solve missing neutrino mystery
Milk from grass-fed cows may be better
Crabs caught spying on rivals' love claws
Lifestyle may not boost breast cancer gene risk
'Trade-off' gene for plants discovered
Pacific islands growing, not sinking
Caffeine addicts get no real perk
Velvet worm's deadly slime revealed
SpaceX cleared for Florida lift-off
Cyborg rights 'need debating now'
Sunlight shines on silver technology
Mountain biking as risky as football, diving
Dusty simulations may reveal planets
Legal fight over breast cancer gene
Unions call for urgent nano information
Solar panel attraction deadly for insects
Meat eaters munched many ways: study
Snakes may be in decline worldwide
Dogs dumbed down by domestication
Fossil sheds new light on 'dino-bird'
DNA 'spiderbot' is on the prowl
GM cotton use increases fruit pest problem
Warming to kill off a fifth of all lizards
Super massive black hole given the boot
Ball lightning could be 'all in the mind'
Immune system could be used to test for TB
Mobile phone cancer link unclear, study
Teen brain wired to take risks
Synchrotron probes Egyptian beads
Argonauts 'gulp' air to swim freely
Space station gets a new room
'Digital genome' to protect dying data formats
Sweep yields leads for new malaria drugs
Researchers snap signs of illegal fishing
Spectrum reveals supernova surprise
Scientists create synthetic life
Eavesdropping a waste of energy
Star caught eating its offspring
Megafauna die-off may have cooled planet
Hepatitis C no longer 'death sentence'
Atoms bring quantum computing closer
Visualisation staves off constant craving
Experts debate homeopathy funding
Visit Statistics