Human intelligence cannot be explained by the size of the brain’s frontal lobes, claim researchers.

New research into the comparative size of the frontal lobes in humans and other species has determined that the size of our frontal lobes cannot solely account for humans’ superior cognitive abilities.

The frontal lobes are an area in the brain of mammals located at the front of each cerebral hemisphere, and are thought to be critical for advanced intelligence.

The study by Durham and Reading universities in UK suggests that supposedly more ‘primitive’ areas, such as the cerebellum, were equally important in the expansion of the human brain.

These areas may therefore play unexpectedly important roles in human cognition and its disorders, such as autism and dyslexia, researchers said.

“Probably the most widespread assumption about how the human brain evolved is that size increase was concentrated in the frontal lobes,” lead author Professor Robert Barton from the Department of Anthropology at Durham University, said.

“It has been thought that frontal lobe expansion was particularly crucial to the development of modern human behaviour, thought and language, and that it is our bulging frontal lobes that truly make us human. We show that this is untrue: human frontal lobes are exactly the size expected for a non-human brain scaled up to human size. This means that areas traditionally considered to be more primitive were just as important during our evolution. These other areas should now get more attention. In fact there is already some evidence that damage to the cerebellum, for example, is a factor in disorders such as autism and dyslexia,” Barton said.

The scientists argued that many of our high-level abilities are carried out by more extensive brain networks linking many different areas of the brain.

They suggested it may be the structure of these extended networks more than the size of any isolated brain region that is critical for cognitive functioning.

The study was published in the Proceedings of the National Academy of Sciences (PNAS).