Research Hit: Brain Areas for Reasoning Identified
New research gives clearest map of regions associated with reasoning in the brain
Surely this isn’t the first time we’ve identified brain areas for reasoning? This sound like the sort of thing that researchers would have been doing since the beginning of time?
Indeed, there has been plenty of research into various cognitive functions and also reasoning but there is also surprisingly limited research on general reasoning. There are also multiple issues with previous research.
Firstly a lot of early research was in very small population groups. Secondly a lot of research is in healthy individual which gives good correlation data but may not point to causation.
Which is why this research is very interesting.
I’m intrigued - tell me more
First on the scale of this study, Joseph Mole and colleagues of University College London recruited 247 patients with unilateral focal brain lesions in either the left or right frontal (front) or posterior (back) regions of the brain. This gives an unusually large set (for this type of research) with focused damage to regions in the brain. There was also a control group of 81 healthy individuals.
These then conducted two types of reasoning tasks while having their brains scanned. these were:
A verbal analogical reasoning task where participants are asked to find relationships between words to solve problems, For example: "If Sarah is smarter than Diana and Sarah is smarter than Heather, is Diane smarter than Heather?."
A nonverbal deductive reasoning task where participants are asked to use pictures, shapes or numbers to figure out logical patterns and solve problems. For example: "Which set of numbers is 1,2,3 most similar to -- 5,6,7 or 6,5,7?."
This gave us a clear indication of which regions and networks are used in reasoning tasks. And it may be a surprise to the lay person.
In what way?
What regions, left or right, are associated with rationality and analytical thinking?
Well, the old trope is that the left hemisphere is the analytical part of the brain, and the right the creative and emotional side. But you have also written about this myth before.
Yes, many people would associate the left hemisphere with analytical thinking but also reasoning and various aspects of decision making such as the left orbitofrontal cortex.
But that is not what they found!
Oh, but surely it is the frontal regions which you have written about many times as those are normally considered the more cognitive and executive centres.
Yes, the frontal regions, as we certainly would think, as all research shows that these are involved in multiple cognitive and executive functions.
However, both types of reasoning tasks showed that it was a right frontal network that was involved and critical to these tasks. Those with right prefrontal damage performed significantly worse on these tasks.
Left for analogical reasoning and right for deductive reasoning. From Mole et al. 2025
So the left hemisphere is not the analytical brain?
Well, as I, and many others have already written, that was always a massive oversimplification and we use multiple regions left, and right, for many tasks including those considered cognitive.
Note that these tasks are actually quite complex, including recognising language or numbers, and balancing these and reasoning. As you can see there is not a single reasoning spot but rather an extensive network that is clearly in the right frontal region and it differs between types of reasoning tasks.
But these are also interesting for another reason.
What?
They noticed a large overlap with networks that are associated with what is known as fluid intelligence. Fluid intelligence is being able to solve problems without any prior knowledge using memory and comparative abilities (in contrast to deducting relationships for example).
This suggests a shared neural basis.
So our right frontal is where reason sits!
Yes, this points to that. It deepens our knowledge of the brain and reasoning but also helps with screening for cognitive disfunction.
Here’s to having a well functioning right frontal network!
Reference
Joseph Mole, James K Ruffle, Amy Nelson, et al.
A right frontal network for analogical and deductive reasoning.
Brain, 2025
DOI: 10.1093/brain/awaf062