The internet is changing the way the human brain works, researchers have found. It is improving people’s ability to make snap decisions and filter large amounts of information – but at the cost of subtle skills such as picking up the nuances of facial expression.

Overall, a new study concludes, the brains of those tested were markedly more active when carrying out internet searches than when reading books.

However, the stimulation was concentrated in the areas that control decision-making and complex reasoning. Areas linked to abstract thinking and empathy showed virtually no increase in stimulation.

Gary Small, director of the memory and ageing research centre at the University of California, Los Angeles, who carried out the research, said that, while computers have marked benefits in stimulating the brain, their use needed to be moderated.

There was a possibility, he argued, that the saturation use of digital technology could lead to long-term evolutionary change.

“Young people are growing up immersed in this technology and their brains are more malleable, more plastic and changing than with older brains,” said Small.

“The next generation, as [Charles] Darwin suggests, will adapt to this environment. Those who become really good at technology will have a survival advantage – they will have a higher level of economic success and their progeny will be better off.”

Small is to publish his findings in the American Journal of Geriatric Psychiatry. He has set out his arguments in more depth in a new book, iBrain.

His claims reignite the debate about the effects of technology on the brain. Some scientists have blamed computer games for the growth of attention deficit disorder among children.

Small scanned the brains of 24 volunteers. He found that browsing websites stimulated the frontal, temporal and cingulate areas of the brain, which control complex reasoning. Older users and those who had not previously tried the internet all showed similar effects.

Baroness Greenfield, director of the Royal Institution and author of ID: The Quest for Identity in the 21st Century, said: “The hypothesis in iBrain is that natural selection will weed out people with brains that are more emotional or more capable of abstract thought and that we will be left with people who are more autistic in tendency. I would agree.”

However, Igor Aleksander, emeritus professor of neural systems engineering at Imperial College London, said: “It may be that by using the internet you stimulate different parts of the brain. However, it would be difficult to show this could not be achieved through other situations.”