Nature, Nurture, and Identical Twins (with David Bessis)

The debate over the role of genetics versus environment in determining intelligence and other traits has been a long-standing one in the field of psychology and genetics. The idea that genetics play a significant role in determining an individual’s intelligence has been supported by studies of twins reared apart, which have found that identical twins raised in different environments still have similar IQ scores.

However, mathematician and author David Bessis challenges this idea in his essay “Twins Reared Apart Do Not Exist: The Shaky Science of Genetic Determinism.” Bessis argues that the studies of twins reared apart may not be as conclusive as they seem, and that the role of genetics in determining intelligence is not as straightforward as some may believe.

Bessis points out that the studies of twins reared apart were conducted in the 1950s, 1960s, 1970s, and 1980s, and may not accurately reflect the complex interplay between genetics and environment. He notes that while genetics do play a role in determining intelligence, there are many other factors at play, such as upbringing, education, and life experiences.

Bessis also challenges the idea that great mathematicians and thinkers are simply born with a special talent, arguing instead that their success is the result of hard work, practice, and a unique approach to problem-solving. He believes that almost anyone can excel in mathematics if they approach it correctly and put in the necessary effort.

Overall, Bessis’s essay raises important questions about the role of genetics in determining intelligence and other traits. While genetics certainly play a role, it is clear that there are many other factors at play, and that the nature versus nurture debate is far more complex than many may believe. The conversation between Russ Roberts and David Bessis delves into the complex relationship between innate abilities and the journey one takes to achieve greatness. Bessis, a mathematician, challenges the notion of innate genius, suggesting that it is the unique experiences and challenges one faces that ultimately shape their abilities.

Bessis uses the example of Bill Thurston, a renowned geometer who overcame a physical challenge in childhood to develop a unique perspective on the world. Thurston’s journey, filled with perseverance and dedication, led him to become one of the most famous geometers of the 20th century. Bessis argues that Thurston’s story highlights the importance of individual experiences in shaping one’s abilities, rather than relying solely on innate talent.

The conversation also touches on the concept of genetic determinism, particularly in relation to intelligence. Bessis challenges the idea that IQ is solely determined by genetics, suggesting that there is still room for individual agency and choice in shaping one’s destiny. He emphasizes the importance of looking beyond simplistic percentages and considering the complexity of human development.

Overall, the discussion between Roberts and Bessis sheds light on the nuanced interplay between genetics, personal experiences, and achievement. By challenging traditional notions of genius and intelligence, Bessis encourages a more holistic understanding of human potential and the factors that contribute to success. In a simple graphic representation, the X-axis represents a person’s polygenic score, while the Y-axis represents their actual phenotype or outcome, such as IQ. The correlation between these two factors is known as heritability, with a 50% correlation coefficient indicating a weak relationship. Despite this, individuals with an average polygenic score still have a chance of achieving exceptional outcomes, such as being in the top 1%.

However, the question remains: what factors account for the remaining variability in outcomes? While genetics play a significant role, there are other non-genetic parameters at play that are not easily categorized into simple socioeconomic criteria. Factors such as family dynamics, individual experiences, and personal idiosyncrasies also play a crucial role in shaping an individual’s development and outcomes.

Eric Turkheimer, a behavioral geneticist, proposed three laws that shed light on the complex interplay between genetics, family, and individual experiences. The first law states that everything is heritable to a certain degree, highlighting the role of genetics in shaping traits and outcomes. The second law emphasizes that the family you are born into may matter less than your genetic makeup, challenging traditional views of social determinism.

However, it is the third law that offers a unique perspective on individual variability. This law suggests that a significant amount of variability in outcomes is neither genetic nor familial but rather a result of individual experiences and life events. From chance encounters to personal interests and relationships, these unique factors shape who we are and play a crucial role in determining our outcomes.

When studying siblings, researchers have found that the correlation between siblings is not as high as between identical twins raised together. This variability in outcomes among siblings underscores the complex interplay of genetic, familial, and individual factors in shaping an individual’s development. While family dynamics certainly play a role, the unique experiences and idiosyncrasies of each individual also contribute to their outcomes.

Ultimately, the interaction between genetics, family, and individual experiences is a complex and dynamic process that shapes who we are and what we become. By recognizing the multifaceted nature of human development, we can gain a deeper understanding of the factors that influence our outcomes and appreciate the unique journey of each individual. The debate over nature versus nurture has been a long-standing one in the field of psychology and genetics. How much of who we are is determined by our genes, and how much is influenced by our environment and upbringing? It’s a complex question that has fascinated researchers for decades.

When we consider this question from a developmental perspective, we must acknowledge the complexity of the human brain. It is a non-linear machine that develops over decades, making it a dynamic and multidimensional problem. The brain is stochastic, meaning that outcomes are not always deterministic. This instability adds another layer of complexity to the nature versus nurture debate.

One example often used to illustrate the genetic component of traits is height. Height is largely determined by genetics, with factors like nutrition and healthcare playing a role in reaching one’s potential height. In modern societies, there is a strong correlation between an individual’s genome and their height. However, not all traits are as easily quantifiable as height.

Intelligence, for example, is a much more complex trait that is not as easily determined by genetics. Studies on twins raised in different homes have attempted to shed light on the nature versus nurture debate, but the sample sizes are often small due to the rarity of such situations. The most famous study by Bouchard had around 56 pairs of identical twins, a relatively small sample size considering the billions of people in the world.

The allure of these studies lies in their ability to provide a definitive answer to the nature versus nurture question. The idea of a natural experiment, where nature has done the work for researchers, is enticing. However, we must be cautious in drawing broad conclusions from such limited data.

Humans have a natural tendency to seek patterns and explanations for complex phenomena, even when the evidence is limited. The nature versus nurture debate is no exception, as researchers continue to grapple with the intricate interplay between genetics and environment in shaping who we are. The brain remains a mysterious and complex organ, and our understanding of its development is still evolving. The documentary “Three Identical Strangers” tells the fascinating story of triplets who were separated at birth and reunited later in life. The triplets, who were identical in appearance, shared many similarities despite being raised apart. They all married women with the same name, they all had a pet dog, and they all shared a love for basketball. The story is both mysterious and magical, raising questions about nature versus nurture.

This story of separated triplets is not the only case of its kind. The Jim Twins, who were separated at birth and reunited in 1979, also shared uncanny similarities. Both twins were named Jim, both married women with the same name, and they even had a pet dog with the same name. The similarities between the two sets of twins raise questions about the influence of genetics and environment on personality and behavior.

However, when we take a closer look at these stories, we begin to see potential flaws in the research. The Jim Twins were both placed in suburban Ohio families, suggesting that there may have been similarities in the social backgrounds of the families that adopted them. This raises questions about the randomness of the separation and reunification of the twins, and how much of their similarities can be attributed to genetics versus shared environment.

The Bouchard study, which focused on twins reared apart, also faced challenges in its design and interpretation. Twins share nine months in the womb, which can influence their development and behavior. Additionally, the twins in the study were not separated at birth, but rather later in life, which could have influenced their experiences and similarities. The study’s reliance on statistical significance and the replication crisis in psychology also cast doubt on the validity of its findings.

Overall, while stories of separated twins and triplets are intriguing and captivating, they also raise important questions about the nature of genetics, environment, and the complexity of human behavior. It is essential to critically examine these stories and studies to understand the true impact of genetics and environment on personality and behavior. The issue of bias in scientific studies is a critical one, as it can greatly impact the validity and reliability of the results. In the case of the famous twins-reared-apart and twins-reared-together studies, conducted by geneticist and statistician Falconer, the issue of bias was addressed by using a control group of fraternal twins. This control group served as a comparison to the identical twins, allowing researchers to account for any correlations that may exist between twins, whether they are identical or fraternal.

However, in a surprising turn of events, the researchers involved in the study decided not to publish the results of the control group of fraternal twins. They cited reasons such as space constraints and a small sample size, which raised red flags among those in the scientific community. These excuses were deemed implausible and unacceptable, as the inclusion of the control group data was crucial in ensuring the accuracy and credibility of the study.

The decision to withhold the data of the control group was met with skepticism and criticism, as it goes against the principles of transparency and rigor in scientific research. The researchers’ reluctance to share this important piece of information raised doubts about the integrity of the study and called into question the validity of the conclusions drawn from it.

In the world of experimental science, where data is the foundation of knowledge and discovery, the withholding of crucial information such as the results of a control group is simply unacceptable. It undermines the credibility of the study and casts doubt on the motives and intentions of the researchers involved.

Moving forward, it is imperative that researchers adhere to the highest standards of transparency and integrity in their work. The sharing of data, especially when it comes to control groups and potential sources of bias, is essential in ensuring the validity and reliability of scientific studies. By upholding these principles, we can maintain the trust and confidence of the scientific community and the public in the pursuit of knowledge and understanding. The debate surrounding twin studies and their implications on genetic and environmental factors continues to be a topic of discussion in the scientific community. One particular study published in 1990 has raised some eyebrows due to its questionable methodology and lack of transparency.

The study in question focused on the IQ correlation between identical twins and fraternal twins who were raised apart. The researchers argued that fraternal twins could serve as a control group for genetic factors, as they only share 50% of their DNA compared to identical twins who share 100%.

However, the study’s critics have raised concerns about the validity of the data and the conclusions drawn from it. They argue that the methodology used in the study is flawed and does not provide a clear picture of the relationship between genetics and IQ.

One of the main criticisms of the study is the lack of transparency in sharing the data. The researchers did not provide detailed information on how they arrived at their conclusions, making it difficult for other scientists to replicate the results.

Furthermore, the study’s reliance on simplifying assumptions has been called into question. While the researchers attempted to estimate heritability based on the correlation between IQ scores of identical and fraternal twins, the accuracy of these estimates has been debated.

Overall, the study’s findings have been met with skepticism by the scientific community. Many believe that more rigorous studies are needed to fully understand the complex interplay between genetics and environment on cognitive abilities.

In conclusion, the study on twin correlations published in 1990 has sparked a heated debate among scientists. The lack of transparency, flawed methodology, and questionable assumptions have led many to question the validity of the findings. Moving forward, it is essential for researchers to conduct more thorough and transparent studies to shed light on the intricate relationship between genetics and IQ. David Bessis makes an important point about the debate surrounding the impact of genetics and environment on a child’s development. As a parent himself, he understands the desire to believe that our actions as parents have a meaningful impact on our children’s outcomes. The idea that our efforts to instill values, discipline, and guidance in our children may be ultimately irrelevant due to genetic factors can be disheartening.

But, as Bessis points out, parenting does matter. While the debate may focus on the degree of influence that genetics and environment have on a child’s development, it is crucial to remember that parents play a significant role in shaping their children’s lives. From making healthy choices during pregnancy to providing a loving and supportive environment for their children to grow and thrive, parents have a profound impact on their children’s well-being.

Bessis also highlights the importance of recognizing the limitations of studies like the Bouchard study, which may not provide definitive answers due to small sample sizes and other methodological issues. It is essential to approach scientific research with a critical eye and consider the broader implications of the findings.

Ultimately, the debate over nature versus nurture is a complex and nuanced one that touches on fundamental questions about human development and the role of parents in shaping the next generation. While the scientific evidence may continue to evolve, one thing remains clear: parenting matters, and the love, care, and guidance that parents provide can have a lasting impact on their children’s lives. The debate over nature versus nurture has long been a contentious one, with experts and laypeople alike weighing in on the factors that shape our abilities and outcomes in life. While some argue that genetics and inherent traits play a significant role in determining our fate, others believe that environmental factors and personal experiences have a greater impact.

In a recent conversation between David Bessis and Russ Roberts, the two delved into the complexities of this debate, highlighting the nuances and intricacies that often get overlooked in discussions of this nature. Bessis, a mathematician, emphasized the importance of individual journeys and inner experiences in shaping our abilities and successes. He stressed that while external factors may play a role in our development, it is ultimately our internal processes and mindset that determine our trajectory.

Bessis also touched on the idea of scalability in education and parenting, pointing out that interventions often fail to have a lasting impact when applied on a larger scale. He highlighted the importance of personal experiences and individual journeys in shaping our understanding of complex issues, such as mathematics and intelligence. Bessis argued that while external factors may influence our abilities to some extent, it is ultimately our internal processes and mindset that drive our success.

Roberts added to the conversation by discussing the inherent complexity of the world and the limitations of data in capturing the full scope of human experiences. He highlighted the importance of personal narratives and inner journeys in shaping our perceptions and beliefs, noting that our passion for understanding the nature versus nurture debate speaks to our fundamental desire to understand ourselves and our place in the world.

In the end, Bessis and Roberts agreed that while the debate over nature versus nurture may never be fully resolved, it is important to recognize the role that personal experiences and internal processes play in shaping our abilities and outcomes. While external factors may influence our development to some extent, it is ultimately our inner journey and mindset that determine our path in life. By acknowledging the complexity of the world and the limitations of data, we can gain a deeper understanding of ourselves and our place in the world. Understanding the factors that contribute to a person’s abilities and talents has long been a topic of debate. Some attribute these differences to societal influences, while others point to genetics as the determining factor. In a recent interview, David Bessis shared his own experiences and insights on this complex issue.

Bessis recalled a time when he was 17 and enrolled in an advanced math program. Surrounded by exceptionally gifted individuals, he was in awe of their abilities. One classmate, in particular, went on to win a gold medal at the International Math Olympiad, leaving Bessis baffled by his seemingly innate talent. Despite his own efforts, he could not match his peer’s proficiency in solving complex math problems. This experience led Bessis to believe that such exceptional abilities must be genetic in nature.

However, as we fast forward to 2025, advancements in neuroscience and technology have shed new light on the workings of the brain. With a better understanding of how the brain functions and the development of artificial intelligence that can mimic certain brain functions, the mystery surrounding talent and intelligence is beginning to unravel.

Bessis emphasizes the importance of looking beyond ideological beliefs when exploring the origins of talent and intelligence. By dismissing preconceived notions and embracing new discoveries, we can gain valuable insights into the complex interplay between genetics, environment, and individual abilities.

In conclusion, the debate over nature versus nurture continues to evolve as we uncover new insights into the human brain and its capabilities. Rather than attributing talent solely to genetics or environment, it is essential to consider the intricate relationship between these factors. By remaining open-minded and willing to explore new possibilities, we can deepen our understanding of what makes each individual unique.