There is a great cliché that says that we are all the same. And another one that says that each person is unique. But what does biology say about this? If we take as an example the genome, which is the set of DNA in our whole organism, we can understand these statements a little better. If you compare the genome of two individuals of our species, you will find that they are 99.6% identical and 0.4% different. With these figures, it is not unreasonable to say that we are all the same. But what about the 0.4%? This percentage is not insignificant on the scale of 3,000,000,000,000 nucleotides and more than two tens of thousands of genes. This genetic variability - along with many other factors such as lifestyle, social context, and diet - is what makes us unique.
And does all this have an impact on our lives? How do these genetic similarities and differences manifest? The truth is that many of the genomic variations have no known effect on the functioning of the genome. However, a small subset of these variations is sufficient to give rise to some of our differences. From the more noticeable ones, such as the color of our eyes, to the less obvious ones such as our cognition.
But let’s not be reductionist. Genes are not everything. In fact, some studies suggest that the influence of genes on our cognition is more important the higher the socioeconomic status. It is becoming increasingly clear that understanding biology should not involve taking sides in the hereditary versus acquired stupid war. Let’s accept reality as it is: something extremely complex. In the end, the final message is the same: we are what we think, and our thinking is what unites us as human beings. But it is also what separates us. Cognition is both a common denominator and a dividing line.
I would like to tell you much more about the development of our cognition. But it turns out that, unlike Silvia Bunge, I do not specialize in high-level cognitive functions. Nor do I devote my life to understanding how educational experiences and our family environment can modulate our cognition. Luckily, I had the pleasure of interviewing her. Who is Silvia Bunge? This renowned researcher was born in Montreal, Canada. She completed a bachelor’s degree in biology at Yale University. Then she went to grad school at Stanford, where she started doing cognitive neuroscience research. Then she went to MIT for a postdoc and had her first faculty position in psychology at University of California Davis. Her current position in psychology and neuroscience is at UC Berkeley. She runs a cognition lab where she studies higher level cognitive functions like reasoning and goal directed behavior, as well as memory. She does this in both healthy typically developing adults, as well as in children and adolescents. She is also interested in brain plasticity and in how home and educational experiences can modulate our behavior.
Juan García Ruiz: What goes first, the brain or the cognition?
Silvia Bunge: My father was a philosopher of science, and he wrote about the mind body problem. So exactly this, how does the brain support cognition, and I very much subscribe to his ideas. He was a monist, so he thought that the brain is what supports cognition and there’s nothing else. But in his conception, he considered that there are levels of complexity that come to play at those different levels. So you cannot reduce cognition down to molecular interactions. But from molecular interactions you get the emergence of more complex systems at the cellular level, then at the system level, and then you have the final level of complexity that is cognition. The same way the gut produces digestion, the brain produces cognition.
JGR: If I had no access to education at all, how different would my brain be?
SB: There’s been very little research on non-weird populations. Most of the research is based on the population of Western, educated, industrialized, rich, democratic countries. What we do know from behavioral research, is that we see the same behavioral functions that are appearing during development. Numeracy is a good example of that. Kids acquire number systems in the same way regardless of their number knowledge. In a society where people don’t even talk about numbers, you still can see some understanding of number concepts that increase in the same way but maybe just develop on a different timeframe. And the same goes for motor development and language. There are some cultures where people don’t speak to you directly as a child and you learn maybe more slowly. But you ultimately get there. Our brains are very similar. Whatever experiences we are getting, we are slightly tweaking the basic template.
JGR: So even if I hadn’t access to education, my cognition in general terms wouldn’t be that different from that of someone who did have an education.
SB: Absolutely. But you would not develop other features. There’s research on, for example, people who never learned to read. The brain area involved in the transformation of visual words to sounds is not as developed as in someone who did learn to read, even though language is developed anyway.
JGR: But cognition is also constituted of building blocks, so if we don’t acquire certain cognitive abilities, we could lack other skills consequently, right? I guess there’s even some degree of emergence in cognition in a way that a few more simple skills can give rise to a complex cognitive ability.
SB: Yes, of course. If you don’t learn to read, for instance, everything is going to snowball from there: you are not going to read advanced texts, you are not going to develop critical thinking skills and other high-level mental processes.
JGR: Just to be on the same page: what do we consider high level mental processes?
SB: Abilities that allow us to tackle new information, reasoning and problem solving are absolutely at the highest level. Equally important are the ability to focus on relevant information, being able to keep and manipulate information in working memory, and the ability to draw on the past richly detailed episodic memories.
JGR: You conduct a study involving children and teenagers from 6 to 19 years old to track the changes in their brain that allow the emergence of high-level mental processes high level. What are the conclusions of this study so far?
SB: Some of our most recent findings suggest that there are individual differences in anatomy that are going to influence the trajectory of the brain. Lately, we’ve been looking at the sulci, so the wrinkles in the brain. These form quite late in development, and we think that they’re fairly sensitive to the environment. We found that whether you do or don’t have specific sulci, or what they look like, does predict the growth of your reasoning over time. There are some anatomical differences between people that influence what is or what isn’t possible for the developing brain.
Beyond that, one thing we’ve looked at closely is the development of the very front of the brain, the rostral lateral prefrontal cortex, and its connections to parietal cortex. We’ve found that strengthening of these connections in terms of white matter and in terms of functional coupling are both good predictors of reasoning development.
JGR: Can you tell me more about this relationship between the sulci and cognition with an example?
SB: I’ve been obsessed with a sulcus located in the rostral lateral prefrontal cortex for 15 years. Some people have this sulcus, and some people don’t. It turns out that the people who do have it have around 30% higher reasoning ability. We found this in kids and adolescents and we published that. And now we just found it in a separate sample of adults as well. We think that there are probably bidirectional relationships between sulci formation and white matter development. The sulci form when the white matter tracts are forming and that creates physical tension in the brain. In addition, in some sulci the white matter is inserted into the cortex, and those short-range connections could reflect more local processing of information.
Beyond that, the depth of different sulci in the prefrontal cortex is associated with reasoning as well. And concerning the cortical gray matter thickness within the sulci we do find changes associated with the development of reasoning.
JGR: Concerning higher cognition, what are the most exciting findings you have found?
SB: We did a series of studies looking at whether reasoning ability could be trained. We were interested in looking at a real-world example of that. We went with this course, that’s very common here in the United States, to prepare you to get to law school. The reason we picked this is because it’s all focused on critical thinking and abstract reasoning. We wanted to know whether studying for this exam over a period of time like three months, could strengthen this reasoning network in the brain. And if this improvement could be transferred to other tests.
We published a series of papers showing improvements on completely different reasoning tasks. In the law school admission tests the problems to solve are all verbal. But then we also found improvements in nonverbal visual reasoning tests. We also showed increases in white matter in prefrontal and parietal cortices and increased functional coupling between these regions. With fMRI, we showed decreased activation of a region of the prefrontal cortex that is associated with difficult decision making.
JGR: What do we know about home environment and the development of higher condition?
SB: A lot of people have been looking at this in the context of poverty. If you look at the papers closely, on average, people who live in poverty have lower cognitive skills. But there’s a huge variability across the socio-economic spectrum. In our work, we found something that was unexpected: we have seen in typically developing kids an interesting brain – behavior relationship. By typically developing I mean, the typical samples who come into the laboratory, which are usually middle – upper class and normal schooling because they are more prone to participate in this kind of research. So most of what we know about brain development comes from these kids. In that work, there’s a pattern of connectivity between two brain networks, that is associated with better cognitive ability. One of the brain networks is involved in focused task performance, and we call this the executive function network. The other one is related with internally guided thought, which is involved in introspection about yourself, like when you are thinking about the past or the future and you are distracted from a goal. What we have found over and over is that the more dissociated these networks are, the better the cognition. This makes sense because the more you are focused on a goal, the more you want to suppress any kind of internal distraction.
But what is really surprising is that kids in poverty show almost the opposite relationship. It’s really interesting, because in these cases there seems to be an environmental pressure that leads the brain to develop in a slightly different way that confers resilience in these kids. Somehow, they get to the same cognitive outcomes through a different mechanism. We don’t know the underlying mechanism. We think it relates to vigilance. And we have some evidence of this. There’s this other brain network that’s involved in heightened awareness. And there’s a dissociation of this network from the other two networks in kids in poverty that could maybe explain the previous finding.
JGR: What are the networks you just referred to?
SB: The one involved in task goals is the lateral frontal parietal network. The one involved in the introspection, we call it the default mode network, and it involves regions located in the middle of the brain. Finally, the regions involved in alerting to some sort of threat or challenge, which are part of the so-called singular particular network, include the anterior cingulate and the anterior insula.
JGR: What other environmental factors could have an impact on cognition apart from the economic level?
SB: In one of our studies, we were looking at various environmental variables. Some of the ones that came into play were the danger level in the neighborhood in terms of crime rate, the type and the quality of school they go to, etc. To take the example of the danger level, we showed that the higher the crime rate, the more different these high performing kids were from the typical sample. These relationships are not only present for abstract cognitive abilities, but also for grades and for attention problems that are reported by parents.
JGR: Could some factors account for positive effects on brain and cognitive development?
SB: Of course. First of all, kids in poverty are learning other things. And there may not be things that we are valuing, or even studying. They may be learning to be more self-reliant or creative, or to process more information. There are some ideas around that.
Then more generally, better schooling has been associated with better reasoning ability. We have a review paper on that. Then there is also caregiving, which can be a very important buffer against early adversity.
JGR: Considering the relevance of a proper schooling for adequate cognitive development, are there things that could be implemented to improve the schooling conditions of kids in poverty?
SB: I think the most important thing is to pay teachers a good wage so that most educated teachers work in these schools where kids in poverty are studying. Any kind of quick fixes like a cognitive intervention is not going to have a long-term impact. In the US, they have invested a lot in early childhood. And that’s great, but you can’t stop there. The brain continues to change and is still sensitive to input, so what we need is high quality education at all stages.
Beyond schooling, at an individual level, there are three other important factors that are related to physical health. We can contribute to our cognitive health if we take good care of our sleep, nutrition and exercise. Kids in poverty have access to worse nutrition and get less sleep. And I think sleep especially can make a great difference.
JGR: Is there a book you would like to recommend to the readers?
SB: The book that really got me started on neuroscience was The man who mistook his wife for a hat, by Oliver Sacks. It was the most influential for me. My mind kind of exploded when I read it as an 18-year-old.
JGR: Do you have a final message for the readers?
SB: Your brain is in your hands. What you do repeatedly is going to influence your outcomes. You shouldn’t be afraid to try new things. Your brain is plastic, and you can do things you didn’t think you could do. It’s important to maintain your cognitive ability with new challenges, without forgetting to maintain your physical health as well.