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Research Feature: Do we need language to think? New research suggests that we don’t

Imagine you’re planning your day. You think to yourself, “If I move the meeting with Bill to 2:30, I can finish proof-reading this report and get it to the printer by closing today.”

Because we experience this type of internal monologue, the language system in the brain was believed to be essential for complex thought and planning. New research lead by Dr Alex Woolgar of Macquarie University suggests that this may not be the case.

The ability to think flexibly and to solve novel problems (known as fluid intelligence) is proposed to depend upon a set of frontal and parietal ‘multiple-demand’ (MD) brain regions. These regions are engaged during many types of cognitive activities. Just adjacent, however, there are brain regions that selectively support language processing. Because of this close proximity, it is possible that the language system is the foundation of complex thought and not the MD regions.

To resolve this question, the international team of scientists compared brain scans from 80 patients with brain damage to scans from over 280 healthy individuals. The healthy participants had either performed tasks, such as reading sentences or nonsense words, that engaged the language systems, or memory tasks that activated the MD brain regions. This allowed the team to identify how much brain damage had affected the language and MD centres in each of the patients’ brains.

In their study published on the 29th of January in Nature Human Behaviour, the team revealed that the extent of damage to the MD-system predicted fluid intelligence loss after brain injury, whereas damage to the language system did not. Conversely, only damage to the language system predicted performance on a language task.

As Dr Woolgar puts it, “This strongly suggests that language is not at the core of our sophisticated reasoning abilities. Both our language abilities and our intellectual prowess set humans apart from other animals, and while language may still be critical in the development of intellect, in adults our abilities depend primarily on on our more evolved MD system.”

In the future, the team plan to use brain imaging to understand how the MD regions support complex thought. According to Dr Woolgar, “We know that these regions have a causal role, but precisely what they are doing to give rise to intelligent thought remains to be discovered.”

This research was conducted by scientists from the ARC Centre of Excellence in Cognition and its Disorders (CCD) and the Department of Cognitive Science at Macquarie University (Sydney, Australia), the MRC Cognition and Brain Science Unit (Cambridge, UK), Harvard Medical School (MA, USA), and Favaloro University (Buenos Aires, Argentina).

Graph showing relationship between brain damage and fluid intelligence

Relationship between area of brain damage and fluid intelligence

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