In a recent study from Beijing Normal University, researchers have demonstrated that certain cognitive abilities, particularly those related to metacognition and mentalizing, are significantly influenced by environmental factors, potentially more so than by genetics. The study, published in Cell Reports00388-7), utilized a twin-based experimental model to explore how both genetic and environmental factors contribute to cognitive processing, revealing surprising insights into how we think and understand our own and others’ mental states.
Research has shown that general intelligence, often measured as Intelligence Quotient (IQ), has a significant heritable component, suggesting that genetics plays a substantial role in cognitive capabilities. However, these findings predominantly apply to basic cognitive functions like memory, perception, and attention, which collectively underpin general intelligence.
In contrast, less is known about more nuanced cognitive functions such as metacognition and mentalizing. Metacognition refers to the awareness and management of one’s own cognitive processes, such as learning and problem-solving, while mentalizing involves understanding and interpreting the mental states of oneself and others, crucial for effective social interaction.
These abilities are fundamental to personal and academic success, making them critical areas of study. However, the extent to which these abilities are influenced by genetic versus environmental factors had not been thoroughly explored.
“Past research has suggested that general intelligence—often referred to as intelligence quotient or IQ—has a heritability ranging from 50% to 80%,” said senior and corresponding author Xiaohong Wan of Beijing Normal University in China. “Our study may be the first to demonstrate that a different kind of cognitive ability, known as metacognition and mentalizing, might be much more influenced by environment.”
The study involved 251 healthy right-handed participants, including 65 pairs of monozygotic twins (who share nearly 100% of their genes) and 55 pairs of dizygotic twins (who share about 50% of their genetic variation), all recruited from the BeTwiSt twin database at the Institute of Psychology, Chinese Academy of Sciences. The researchers assessed the participants’ socioeconomic backgrounds, including education levels and monthly income, to control for these variables in their analysis.
By examining the similarities and differences in traits and behaviors between monozygotic and dizygotic twins, researchers can effectively dissect the contributions of inherited (genetic) factors and environmental factors. If identical twins show more similarity in a trait compared to fraternal twins, it suggests a genetic influence. If both types of twins show similar levels of similarity, it indicates a stronger role for environmental factors.
To assess cognitive functions, each participant underwent two distinct tasks: one for metacognition and another for mentalizing. The metacognition task involved participants observing a visual display of moving dots (random-dot-kinematogram) and determining the overall direction of motion. Participants then rated their confidence in their decision, without receiving feedback on their accuracy. This task evaluated their ability to assess and report their own cognitive processes.
The mentalizing task required participants to estimate the confidence that another twin, either their sibling or another participant, had in their decision on a similar task. This was challenging as participants did not have direct information about the other’s choices or confidence levels; they could only rely on observing the response time.
Contrary to the traditionally high heritability observed in general cognitive abilities like intelligence, the researchers found that metacognition and mentalizing are more strongly influenced by environmental factors than by genetic ones.
Specifically, the researchers observed that for tasks involving metacognitive processes, the similarity in performance between twins could be attributed more to their common upbringing and shared experiences than to their genetic makeup. Similarly, in tasks that required participants to assess the confidence levels of others without direct communication (mentalizing tasks), the results suggested that environmental factors were again predominant over genetic factors.
“Our findings were outside our expectations,” Wan said. “Decades of extensive research utilizing the classical twin paradigm have consistently demonstrated the heritability of nearly all cognitive abilities so far investigated. Our findings emphasize that these shared family environmental factors, such as parental nurturing and the transmission of cultural values, likely play a significant role in shaping the mental state representations in metacognition and mentalizing.”
Despite the robust design and significant findings of the study, the researchers acknowledge several limitations. The tasks used to measure metacognition and mentalizing are complex and may not cover all aspects of these cognitive abilities across different contexts. Furthermore, the effect sizes and statistical powers were modest, suggesting that larger studies might be needed to confirm these findings.
Future research is encouraged to explore these cognitive functions using different tasks and larger, more diverse samples. Additionally, integrating genetic data through genome-wide association studies could further elucidate the genetic underpinnings of these cognitive abilities.
The study, “Distinct genetic and environmental origins of hierarchical cognitive abilities in adult humans,” was authored by Shaohan Jiang, Fanru Sun, Peijun Yuan, Yi Jiang, and Xiaohong Wan.
