New US research suggests that the part of the brain which inhibits reckless behaviour may not be fully developed until 25 meaning that young drivers may underestimate risk.
The brain imaging study led by the National Institutes of Health examined the physical development of grey matter as children between the ages of 4 and 21 grow.
It found that the brain areas involved in processing sensory data developed first and the orbitofrontal cortex used to integrate the information - at the front of the brain just behind the brow - developed last.
Summarising their findings, the author say: "Parts of the brain associated with more basic functions matured early: motor and sensory brain areas matured first, followed by areas involved in spatial orientation, speech and language development, and attention (upper and lower parietal lobes). Later to mature were areas involved in executive function, attention, and motor coordination (frontal lobes)."
The study suggests that, while most western societies put the age of intellectual maturity at 18, it could be seven years later before the "age of reason" is reached on to risk assessment.
Attorneys cited this research to the US Supreme Court prior to its decision in early March to end the death penalty for youths who committed murder aged between 16 and 17.
Dr Jay Giedd, the paediatric psychiatrist leading the NIH study, stressed that, while there is no proven link between brain development and behaviour, it was "time to bring neuroscience into the driver safety debate."
He believes the data which shows the brain developing in "spurts" could also be important to understand when the brain is at its most receptive to learning vital skills, such as driving.
Dr Hugh Garavan, director of functional brain imaging at Trinity's Institute of Neuroscience, said the study was an "exciting scientific endeavour", but cautioned against a premature extrapolation of its findings into social policy areas like road safety strategies.
"I'm in favour of this type of research but I would be cautious about basing social policy on these types of results." He highlighted limitations with the NIH study and said further research was required. The study was based on just under 2,000 anatomical models of the brain, composed from magnetic resonance imaging scans from just 13 children.
"The robustness of the effects needs to be confirmed," he said. "This requires replication with other participants in other labs. There may also be sizeable individual differences in development; on average, 18-year-olds may have smaller grey matter volumes in particular brain regions than 21-year-olds but how diagnostic or informative is this for any one individual 18-year-old?"
What is not in question is that car crashes kill more under 24-year-olds than any other group. In 2003, the most recent year for which data is available, 85 people between 15 and 24 died on Irish roads. The next age group, 25-34, had 65 deaths in crashes while just 31 in the 35-44 group died on the roads. This sequence is repeated in each of the past four years.
Conor Faughnan of AAroadwatch says the "heavy over-representation of young drivers in the crash statistics has been known for a long time. What the NIH research indicates is another possible reason why that is so. This kind of research could be important for improving the way young drivers are taught."
Brian Farrell of the National Safety Council said the research reinforces "the need to concentrate on hazard awareness skills rather than learning the rules of the road by rote".
