Mapping Brain Networks Behind Complex Reasoning

Researchers have discovered why humans excel at “relational reasoning,” the ability to detect patterns and relationships in order to make sense of seemingly unrelated information. The study is published in the journal Neuron.

Relational reasoning — not found in other animals or even primates — is a high-level cognitive process in which we make comparisons and find equivalencies, as one does in algebra, for example.

For the study, scientists from the University of California in Berkeley found that subtle shifts in the frontal and parietal lobes of the human brain are linked to superior cognition.

The frontoparietal network plays a key role in analysis, memory retrieval, abstract thinking, and problem-solving, and has the flexibility to adapt according to the task at hand.

“This research has led us to take seriously the possibility that tweaks to this network over an evolutionary timescale could help to explain differences in the way that humans and other primates solve problems,” said lead investigator and neuroscientist Dr. Silvia Bunge.

“It’s not just that we humans have language at our disposal. We also have the capacity to compare and integrate several pieces of information in a way that other primates don’t,” she added.

For example, humans identify the relationship between two items or activities in one of the following ways: semantic (hammer is used to hit a nail); numeric (four is greater than two); temporal (we get out of bed before we go to work); or visuospatial (the bird is on top of the house).

We may take this further and make higher-order comparisons by comparing two or more sets of easier associations (a chain is to a link as a bouquet is to a flower).

After reviewing dozens of studies, including their own, the researchers concluded that anatomical changes in the lateral frontoparietal network over millennia have served to boost human reasoning skills.

“Given the supporting evidence across species, we posit that connections between these frontal and parietal regions have provided the necessary support for our unique ability to reason using abstract relations,” said co-author Dr. Michael Vendetti, a postdoctoral researcher in neuroscience at University of California, Berkeley.

To test this theory, the researchers examined studies that track anatomical changes in the developing human brain; compare neural patterns in human and non-human primates, and compare how human and non-human primates tackle a variety of reasoning tasks.

Their large meta-analysis identified three parts of the brain that play key roles in relational reasoning: the rostrolateral prefrontal cortex, the dorsolateral prefrontal cortex, and the inferior parietal lobule, with the rostrolateral region more actively engaged in second-order relational reasoning.

Among the behavioral studies they analyzed, humans were found to use higher-order strategies to guide their judgment while primates relied more heavily on perceptual similarities and were slower at reasoning and problem-solving.

“These results do not necessarily prove that non-human primates are unable to reason using higher-order thinking, but if it is possible to train non-humans to produce human-like performance on tasks associated with higher-order relational thinking, it is certainly not something that comes naturally to them,” said the researchers.

Source: University of California, Berkeley

Abstract reasoning concept photo by shutterstock.