New research published in communication biology It suggests that people who perform well on intelligence tests may have brains that can communicate more flexibly across distant regions. The study found that more diverse connections between major brain regions and more complex patterns of brain activity over time were associated with higher intelligence scores.
Researchers have long sought to understand the biological basis of intelligence. Early research often focused on identifying specific brain regions responsible for higher cognitive abilities. In particular, the frontal and parietal lobes are often associated with reasoning, problem solving, and complex decision making. More recent theories suggest that intelligence may also depend on how flexibly brain networks can shift between different patterns of activity when solving problems.
The researchers behind the study, led by Jonas A. Thiele of the University of Wurzburg in Germany, wanted to test these new ideas more directly. Specifically, we aimed to provide the first empirical test of the newly proposed multilayer processing theory of intelligence (MLPT), which suggests that human intelligence relies on processes operating across multiple spatial and temporal scales.
Rather than studying brain activity while people were resting or performing simple tasks, they looked at brain activity while participants completed a well-known intelligence test called Raven’s Progressive Matrix. In this test, participants must look at a pattern of shapes and decide which parts correctly complete a logical sequence.
To investigate these multiscale brain processes, the scientists analyzed two different datasets collected in separate laboratories. In the first dataset, the brain activity of 67 participants (26 women, mean age 23 years) was measured using functional magnetic resonance imaging (fMRI) while taking an intelligence test. The method tracks blood flow in the brain, allowing researchers to see which regions communicate with each other through different spatial networks during tasks.
In the second dataset, 131 participants (65 women, average age 24 years) completed the same type of reasoning test and had their brain activity recorded using electroencephalography (EEG), which measures electrical signals produced by the brain. Unlike fMRI, EEG can capture very rapid changes in brain activity, allowing researchers to study how the complexity of brain signals changes over time.
The fMRI results revealed a crucial nuance. It turns out that people who score high on intelligence tests don’t just have “stronger” connectivity throughout their brains. Instead, they demonstrated more diverse communication between frontal and parietal regions of the brain. These regions appear to act as highly efficient “connector hubs” linking disparate brain networks to coordinate information as participants solve complex problems.
EEG analysis revealed that individuals with higher intelligence scores exhibited greater signal complexity on longer (coarser) timescales, suggesting richer and more flexible large-scale brain dynamics. At the same time, we observed a weaker and non-significant trend of reduced complexity on very short (fine) timescales. This may reflect simpler and more efficient local processing within smaller brain circuits.
Together, these results support the idea that intelligence is not derived from a single brain region, but from how different regions work together effectively across different spatial and temporal scales.
Thiele et al. concluded that: “Our findings provide the first empirical evidence for a key assumption of multilayer processing theory (MLPT), which posits that higher intelligence arises from more flexible global long-range processes operating on coarser timescales and coordinating simpler short-range processes within smaller neuronal ensembles on finer timescales.”
Despite these insights, the researchers caution that the study has several limitations. For example, the fMRI scans and EEG recordings were obtained from different participant groups, so it was not possible to directly compare the two datasets. Additionally, the relatively small sample size may limit statistical power, and all participants were young, so the results may not necessarily generalize to children or older adults.
The study, “Deciphering the Human Brain During Intelligence Tests,” was authored by Jonas A. Thiele, Joshua Faskowitz, Olaf Spons, Adam Chudarsky, Rex Jung, and Kirsten Hilger.
