Brain development - decisions, decisions...
This month, we're talking development and decisions. From some of the cellular decisions involved in actually making a brain, to delving into teenage decision making...
In this episode
00:55 - Are online strategy games good for my brain?
Are online strategy games good for my brain?
Duncan Astle, Cambridge University; Helen Keyes, Anglia Ruskin University
We pick apart some of the latest neuroscience news with the help of local experts, cognitive neuroscientist Duncan Astle and perceptual psychologist Helen Keyes. First up, Helen looked at a paper this month about how, she says, playing video games can turn you into a super-perceiver!
Helen - Many millions of us play action, real-time strategy games. People who play these games often play them for quite sustained amounts of time and there's growing evidence really that playing these games can really be very beneficial for your cognitive function. So there are many cognitive benefits associated in general with playing action video games. It improves our hand eye coordination, our visual processing. It makes people better at detecting fast moving objects and identifying stimuli in your peripheral vision. So there's really a wealth of these processing benefits to action video games. But this study wanted to look at the effects of what we call action, real-time strategy games. So these are games that involve a lot of fast-paced action but also involve the player making real-time strategic decisions very quickly. The authors were hypothesizing that this type of gaming would benefit not only your spacial attention skills but what we call your temporal visual attention. So that is the idea that you might be able to perceive and process information more quickly than non video game players. And to do this, the authors used what we call an attentional blink task. So attentional blink happens to us all. If we're processing one thing and we are presented with something else really quickly after that, about 200 to 500 milliseconds after that, you just can't really process it. We call it an attentional blink. Your brain is basically blinking, processing the first thing. So this study was using the attentional blink task to look at whether people who were really masters at playing these action strategy games, whether they suffered less from this attentional blink.
They looked at 19 players who were in the top 7% of players worldwide on the leaderboards. They compared these people to 19 other League of Legends players, video game players, but these were non-experts: so they'd only been playing for less than six months and the rankings weren't very high. They presented all of these people with attentional blink tasks, so a series of numbers or letters where your job as the participant would be to identify when a target letter came up. So the letter D for example, you'd have to respond to that if it came up. They presented you with these tasks. If I was attentionally blinking, I'd miss the second stimulus. And while they were doing that, they recorded EEG. So as we know, EEG records the electrical activity in your brain and is really good at tying down exactly when your brain responds to something. And they found that expert video game players suffered less from attentional blink than non-experts. That is, they recognized more of these second targets: they were blinking less attentionally. And interestingly, this was also reflected in their brain activity. So their response, what we call their P3 response in their brain, which is a response that happens about 200 to 500 milliseconds after you see something, that response to the second target was much quicker in expert video game players and it was stronger as well, it was bigger.
This suggests that not only can expert video players respond more quickly to targets, but that they have more attentional resources available to make decisions in rapid succession. So these expert video game players were able to make a quick decision, identify a target, and then make another decision really quickly after that because they'd practiced this skill quite a lot. During the pandemic lots of us will be playing more video games than usual. So it's good to know that we can do so guilt-free because we are really just developing our cognitive skills. But it's a nice answer to the moral panic that sometimes is associated with this extensive video game playing.
Katie - To hear that there are cognitive benefits to gaming is really exciting. I'm wondering where the catch is in terms of people who do suffer from gaming, do you know if there's any evidence to suggest that people who game too much have any cognitive disadvantages?
Helen - Well you've hit the nail on the head in that most of the downsides associated with extensive game-playing are behavioral kind of social downsides. When, when it comes to the cognitive downsides, there really haven't been many that have been documented. So when we look at large scale meta-analyses of a video game playing and their effects on your cognitive skills, people have either found no effect or a positive effect. So there aren't really any suggestions that this can be bad for your cognitive processing. But of course other types of social scientists would look at this from a different perspective. Looking at, you know, how much time you're spending gaming and how that may be affecting your social skills. That's certainly not my area of psychology, so I wouldn't want to comment on that. But in terms of the cognitive effects, it seems to be pretty much all roses.
As you're listening to someone talking, the theory is that your brain is making moment by moment predictions about what word is coming…. next. But what is the brain making predictions about? Individual words, categories of words? This is precisely the question posed in the paper that Cambridge University's Duncan Astle looked into this month, and he told Katie Haylor about it.
Duncan - So what the authors did is they placed subjects in an MEG scanner or a magnetoencephalography scanner, which is a type of brain imaging that's very quick and rapid. And then they played them different types of sentences. So the sentences could be things like... could have the phrase in them 'such and such they cautioned the...' and then you're expecting a word at the end. And because of the type of verb that it contains, so 'cautions', you expect that the word that's coming is animate in some way. So it could be like a person's title or you know, 'they cautioned the man', 'they cautioned the woman', those sorts of sentences contrasted with sentences like 'they caught the,' it'd be more likely to have something like 'they caught the ball'. And so subjects would be sitting inside the MEG scanner as they heard these different sentences. And in that moment, that split second after the verb, so after 'cautioned' or 'caught' and before the final noun arrives before the final kind of naming word at the end of the sentence, they wanted to see what is the brain predicting. Is it able to predict that the final word is going to be animate like man or woman? Or is it going to able to predict that it's going to be inanimate, like ball? Or does it make no prediction whatsoever? So that's what they really wanted to know. And what they were able to show is that in that split second, the brain is making a prediction that is specific to whether it's an animate word that it's expecting to come next, or an inanimate word that it's expecting to come next. But it's not able to make a prediction about more specifically what word is coming next, which suggests in that moment what's being made is a very course, general prediction that takes into account the kind of semantic properties of the word that it's expecting next, but it's not as specific as an individual lexical item that's coming next.
Katie - Do we know why this might be important?
Duncan - Language is incredibly rapid and dynamic, and if our brain is constantly just reacting to what it hears in a passive way, that's an incredibly inefficient way of doing it. So for instance if your brain makes no predictions and it just waits for words to arrive at it and then it tries to decipher what they mean, every time it's kind of starting an exhaustive search of all the words it knows to see which one matches what you've just heard. Whereas if you can make a prediction about what words are coming next, then in a way you're narrowing down massively the kind of repertoire of words you're going to have to access when that word arrives. And the more you can narrow it down, the better your prediction is, the more quickly and the more rapidly you can process the information. And ultimately that's how you and I are able to kind of maintain rapid conversations because our brains aren't just sort of passively waiting for what's coming next. They're actually making a dynamic prediction about what's coming next and that's how they're able to respond so quickly.
Katie - How significant do you think this is in terms of our understanding of how language works?
Duncan - I think it is significant in the sense that there are various very contentious debates about what the brain is doing in a moment by moment sense. But actually lots of the neuroscience or the neuroimaging measures that we use are super slow, right? So we often talk about FMRI and you see these pictures of people's brains with colourful blobs in them. Those are all usually gathered over the order of seconds, right? And so you've got no way of knowing whether the information that that reflects is something that the brain was predicting, or the brain was responding to, or a combination of the two. And the really nice thing about this study is because they are using magnetoencephalography and then they repeat it again with another technique called electroencephalography - which is electrodes stuck on the side of the head - and they show exactly the same effect, because they are using those sorts of rapid new imaging technologies it really enables them to say actually it's a prediction that the brain is making. I think that's what's really nice about this study.
How cells decide their fate
Afnan Azizi, KCL and The Francis Crick Institute
In order to be here today deciding to listen to this podcast and incredibly complex decision making cascade occurred in your mother's womb before you were even born. And it can be rather difficult to pinpoint exactly when during development in the uterus, the brain is actually formed.
Afnan - I would say a brain is not really a brain until probably the beginning to middle of the third trimester because all the neurons and all the connections of the neurons haven't actually formed until that time.
Katie - That's developmental biologist Afnan Azizi who works at KCL and The Francis Crick Institute trying to understand what's going on in very early mammalian brain development. So what is involved in getting us from a fertilized egg cell to a human being? Well a lot obviously, but what Afnan is particularly interested in is the cellular decisions being made during this very early brain development process. And we're talking from just a few weeks when a woman might not even realise she's pregnant yet.
Afnan - The way I think about it is a series of decision-making from cells of what kind of cells they're going to become, what kind of connections they're going to make with their neighbouring cells and you know, farther off cells, and how these connections are going to be strengthened or weakened. So when you start off from a single cell, this cell divides - at some point, you end up with these three layers. Each of them are going to give rise to different body organs. The outside layer, which we call the ectoderm, that gives rise to the skin and the nervous systems, the middle layer, the mesoderm, that gives rise to the bones and the muscles and cartilage and things like that. And the inside layer, the endoderm, which has the gut and the respiratory system and those things covered.
Katie - Right so if we all start off as these incredible balls of stem cell potential, how do some cells know to turn into a brain cell whereas others will be a lung cell or a heart cell? Afnan explained.
Afnan - You have a large number of molecules, proteins that are made from the genes, and a lot of these are the same across various species and these molecules, at different time points and at different parts of the body, are expressed in a way that they form a location system. Imagine if you had multiple coloured paints and you drew a massive red circle on one side of the street and a very small circle on another side. Then on the second side you drew a really big green circle. Then you actually have now a system that tells you what part of the street you're on and you can point to different addresses based on how much green or red you have. It's a very similar system. The way it works is you go from creating a very generalized area. So like I just said, the three layers, one of them is like skin and neuron cells, which is obviously very different things, but you're slowly restricting the type of cells that they will become. So at the beginning you have a ball of cells that have no identities associated with them, and then you send a signal, say, okay, well the one that's on top is going to become this ectoderm for example, and it's going to become the skin or a neuron cell.
Katie - This amazing system conjures, in my brain at least, a super complex version of those decision tree quizzes I remember from teenage magazines like "what animal's the perfect pet for you!" Remember? You answer yes or no and eventually you funnel down into either dog, cat or hamster... But Afnan imagines it like a family tree with the original ancestor being that fertilized egg cell.
Afnan - It's the one that can make anything. We call those cells totipotent. So they're 'totally potent' to make all kinds of cells within the body and the placenta, in fact.
Katie - So all sorts of things can influence which cells these stem cells and their intermediate go onto become: what signals they're exposed to, when they're exposed to them, and where the cells are in relation to the signal. But back to the brain. How do the neurons and glial cells and everything else needed for a brain - how do they get made? Well Afnan said it's important here to consider brain axes: top to bottom, left to right and back to front.
Afnan - Very early on at least the left-right symmetry is mostly maintained - so you don't get much difference between what's happening on the left side and on the right side, it kind of comes out a bit later. But the bottom-top, and the front-back symmetry breaks quite quickly. So you get this top-bottom asymmetry broken very, very early on. And that allows the different parts of the central nervous system to be defined. So your brain and your spinal cord are different from each other. So one very important aspect of the brain and the way it works is that you need these different regions. You need these different areas to do different computations, to connect various parts of your nervous system together. And these all come from this breaking of symmetry. And then the other symmetry breaking is the front and back. And that also happens really early on and that's a lot more like complicated, but it is really important because that's what forms the difference between your cortex and like other parts like the hippocampus and the hypothalamus. So a lot of these happen from a lot of these different regions that are important for this work. We talk about neurons of different identities. They don't all come from the same stem cells. Like I said earlier, it's kind of a slow breakdown and slow specialization. It's not that you go from like, 'Oh well I have all these stem cells that all are the same and then one of them is going to become cortex, one of them is going to become cerebellum'. You actually start making more specialized stem cells and those end up in their areas, and then those more specialized stem cells make even more specialized stem cells and more intermediate stem cells. And then finally you make a neuron, for example. Even then you end up specializing those neurons even more by like, okay, well out of these 10 neurons that this one very specialist stem cell made, maybe two of them are gonna like have a different neurotransmitter and then one of them is going to die. So there's a lot of dynamics going on all the way up to like the third trimester and after birth.
Katie - Afnan's particularly interested in the signaling molecules which influence what differentiated cells will eventually come from the starter stem cells. And these molecules are very similar across species like humans and mice, but it's how they used that seems to differ. It's our genes that determine when these signals come on, where they come on, and what subsequent genes these signals can then turn on. Studying very early human development is so important in order to understand more about, for instance, disorders of development. But it's very difficult to study these things directly in humans for ethical reasons. So scientists like Afnan work to compare how early brain development happens across species to ultimately better understand how we are made.
20:15 - Decisions and the teenage brain
Decisions and the teenage brain
Professor Sarah-Jayne Blakemore, Cambridge University
Once we’re born into the world, we grow into youngsters and early adults, and as teenagers we start making an awful lot of decisions about the person we’re going to be. Sarah-Jayne Blakemore is a Cambridge University psychology professor and an expert in the teenage brain, and she spoke to Katie Haylor.
Sarah-Jayne - So there's a lot of change across the entire brain throughout adolescence. The cortex, which is the surface of the brain, undergoes very substantial changes in, for example, the volume of grey matter it contains. We know that in childhood gray matter volume increases and then it peaks in late childhood or early adolescence, around 9, 10 years and then it undergoes a really substantial decline throughout the whole of adolescence and only starts to stabilise in the mid twenties. And at the same time, the amount of white matter in the brain increases linearly throughout childhood, adolescence and even into the twenties and thirties.
What we know less about is what cellular processes underlie these structural changes, but we can make educated guesses based on research on animals and also on postmortem human brain tissue. And we know from that research that a whole host of neurodevelopmental processes are going on throughout childhood and adolescence, including the fact that axons - the long fibers that connect up neurons in the brain - grow in diameter and become myelinated. That is they have a fatty substance added to them. And that increases the amount of white matter in the brain. And at the same time it results in a decrease in grey matter. Another neurodevelopmental process that occurs during adolescence is a reorganisation of synapses. That is the connections between neurons. And we know that synapses hugely expand in number during childhood. And then what happens is that the excess synapses get pruned away during adolescence.
And the really interesting thing about synaptic pruning is that synapses that are being used in a particular environment or the synapses that remain and grow stronger. While synapses that are not being used in a particular environment are the synapses that get pruned away. So in that way, brain development is partly dependent on the environment that you're growing up in.
Katie - It sounds like there's a fantastic amount of change that occurs during these years. Do these changes impacts our decision making behaviour?
Sarah-Jayne - Yeah, so at the same time we know for example that the ability to plan actions, to inhibit inappropriate responses, to remember things, also to take other people's perspectives, and certain forms of self-awareness are all undergoing quite a lot of change and development during adolescence as well. What we don't know is how much that's related to the changes in the brain. We assume that these changes in behaviour are related to the changes in the brain, particularly because the brain regions that undergo the most substantial and protracted changes are in areas like the prefrontal cortex and the inferior parietal cortex that are known to be involved in high level cognitive processes like decision making and planning.
Katie - There's a stereotype that teens make risky decisions. Is this just a stereotype or is there developmental stuff going on to back this up?
Sarah-Jayne - Well, is it a bit of a stereotype in that you can't really generalise about teenagers, just like you can't really generalize about humans. On top of that stereotype, there is evidence to suggest that risk-taking is heightened in adolescence and adolescents do show an increased propensity to take risks. We often worry about risks, the risks that adolescents might take, and that's completely justified worry because sometimes those risks can be dangerous. On the other hand, we learn by trial and error. We learn by taking risks, we explore our environment by taking risks and ultimately we become independent adults by forging our own way through our adolescence and making our own decisions and taking risks along the way. Of course it has to be constrained and we have to educate young people about the potential negative consequences of risk taking. But often it's not a negative thing.
Katie - How significant is the social influences of what your friends' are doing, in this conversation?
Sarah-Jayne - Adolescent risk-taking often depends on the context of the decision making, and adolescents are far more likely to take risks when they're with their friends compared to when they're on their own. So if you think about the risks like smoking and drinking and um, taking drugs or even dangerous driving, those are risks that even adolescent takes them, they're much more likely to take them when they're with their peers than when they're by themselves. We know from lots of studies in labs and also from real life data that risk-taking increases in adolescence when they're with their friends compared with when they're on their own.
Katie - When you say "adolescent", in my head, I'm thinking teenager, I'm thinking 13 to 19. Is that what adolescence is?
Sarah-Jayne - Actually, well the definition of adolescence is not clear cut, but the most recent agreed upon definition is the period of life between 10 and 24 years. So really a very long period in humans! And this definition was developed a couple of years ago by adolescent scientists in Australia at Susan Sawyer and George Patton. And it's partly based on the new knowledge about how the brain develops so substantially across that entire period of life between 10 and 24. And that's the definition of adolescence that I now go with and most of my colleagues do.
Katie - Blimey! So as an expert in the teenage brain then, how arbitrary do you feel the decision is that we are legally an adult at 18 then?
Sarah-Jayne - All these age cutoffs like you know, whatever it might be. The age of criminal responsibility, which by the way is 10 in this country in England and Wales - much younger than most other European countries - age of consent, age of legal smoking, drinking and of course voting and legal adulthood, these are all really quite arbitrarily chosen. Most of these age cutoffs have not been based on what we know about brain development, because they were decided way before we knew anything about how the brain develops during adolescence. So what I would say is that those kinds of decisions about age cutoffs should incorporate the new knowledge about brain development during adolescence.
On the other hand, this is a question I'm asked often, I don't think the neuroscience can provide an age for you. We can't say, "Oh, the neuroscience shows that the brain becomes adult at age 18 or 24" or whatever it might be. It's much more complex than that. I mean, first of all, different brain regions develop at different rates and mature at different rates. So there are big individual differences in the speed of brain development and when things start to stabilise. So what I would say is that what we know from neuroscience is the kind of age range, the very broad age range when the brain becomes mature and adult. And that's much later than 18, between 20s and 30s for most people. So of course that cannot generate an age at which you become legally adult.
Brain development is not, you know, the only factor when considering things like rational decision making and adulthood. One area of discussion is should the voting age be reduced to age 16? And actually there, brain development - it’s relevant, but it’s not critical. What is critical is more psychological factors and ethical factors. Actually, there isn't much in the cognitive development literature that I know of that would argue against voting age being reduced to 16.
Katie - Are there significant gender differences in decision making through adolescence? Because from what I understand, boys can develop a little bit later than girls. Does this have an impact?
Sarah-Jayne - Um, yes. Well boys go through puberty later, on average, later than girls, probably about 18 months on average later than girls. And there is some evidence that the big changes in sex hormones and physical maturity that we all go through in our early adolescence is partly responsible for some of the changes in the brain, rather than your chronological age, how many years you've been alive. And so in some ways you might expect boys, especially in early adolescence, to be developing slightly later than girls. However, interestingly, the evidence is really unclear. Although initially when the first studies of brain development during adolescence were published, there seemed to be some evidence that boys' brains developed a little bit later than girls' brains, actually more recent evidence hasn't replicated that finding. More recent studies with more sophisticated analysis that takes into account, for example, overall brain size and overall cranial size. Once that's taken into account, the gender differences between brain development seem to be much reduced. So actually there isn't really clear cut evidence for gender differences in brain development in adolescence.
30:19 - Sure you made the right choice?
Sure you made the right choice?
Dan Bang, UCL
How does decision-making confidence change as we age and gain more experience? Is it always a good thing to be confident in your choices? Katie Haylor spoke to social neuroscientist Dan Bang from UCL...
Dan - So when we talk about decision making and in particular confidence - which is a feature of cognitive control process, you might say - then we often talk about something called metacognition, broadly defined as thinking about thinking. And more specifically it's the set of processes that are involved when you reflect on, evaluate, and control your on-going thought and behaviour. And metacognition has different features which are going to be relevant for understanding how confidence might change over and how decision making might change over the lifespan. So on one hand we have what we call sensitivity or resolution, which is how good you are telling your correct beliefs from your wrong beliefs. And then on the other hand we have something we call calibrational bias, which is a general tendency for over or under confidence if you like. The former is more related to development, the maturation of neural infrastructure, if you like. Whereas the latter is more tied in with social context and the different social roles that confidence plays.
Katie - I guess both of those things change as we grow up. Right?
Dan - Exactly. So if you think about the sensitivity of our confidence, that's likely to depend on different forms of cognitive function that we know are slow to develop, such as cognitive control or executive function. And then on the other hand, this bias side of metacognition is more tied into the current social context if you like. And as we know, the social context changes dramatically across the lifespan. So the different kinds of functions that confidence might fulfill also going to change. And that might lead to what we think of as stereotype behaviour in different periods of time.
Katie - Can I put something to you? Because I've often heard the metaphor of growing up and confidence being a bit like being a fish in a pond. And so when you're a kid, the pond or your area of influence, the area in which you're sure about things is relatively small, but as you grow up, the pond becomes a lot bigger. So you might feel a bit less confident in your decisions. But that's because your context is so much broader. Does that metaphor have relevance to what you're saying?
Dan - I think it does. So in decision neuroscience, we often think of confidence as a mathematical construct. So when we talk about confidence, we talk about some internal estimate of the probability that a belief or a decision is correct. And in order to compute that quantity, that estimate accurately, you need to have access to all the kinds of information that bear on that hypothesis, belief or decision. And naturally as you world sort of grows, as you gain more knowledge about different domains, you'll realise that there are more and more pieces of knowledge or evidence that should bear on your hypothesis or belief, which naturally I think will lead you to feel less confident about that hypothesis because you realise that you can't have full confidence in it in a sense, I mean obviously in broad terms.
Katie - Are there factors that we know tend to influence how confident we might be at making a decision?
Dan - As the decision grows in complexity, the more factors are going to be at play. So if you have simple decisions, your confidence is likely to be based on all the relevant information there because you have that available to you. So you can compute a more accurate sense of confidence. But as you get to more complex things, other factors are going to be in play. And then we stop relying on what we call heuristics or rules of thumb. We have something called confirmation bias. So if you already believe something, we're more likely to accept evidence or supporting that hypothesis rather than another hypothesis. You also have things like ease of processing. So if a hypothesis seems sort of intuitive to us or if it's easy to understand, we're more likely to think that that's correct. So these are sort of rules of thumb we generally hold, but then when you get to more complex problems can probably lead you into trouble.
Katie - I see. So it sounds like actually making a decision objectively can be pretty difficult.
Dan - Exactly. And I think decision neuroscience went through a phase where we thought of humans as quite silly, making silly decisions. But then when we start recognising that we make decisions under huge resource constraints, we don't have infinite computation available, we don't have infinite time available when you make decisions, then you can start thinking about these different biases or heuristics as quite efficient solutions to what's actually a very difficult problem.
Katie - So how do scientists like yourself study confidence in decision making?
Dan - So again, I think it takes different forms. So what I do in my own work is use simple games based on simple perceptual tasks. So you see a cloud of dots on your screen and you have to say "are they moving to the left or to the right?"Then we manipulate the amount of noise, that sensory stimulus, and then we check whether your confidence sort of tracks the accuracy of your choices about that sensory stimulus. So we try to come up with constraints, scenarios where we ask you questions over and over again, and we can sort of quantify how good are your decisions overall, and then how good are you at evaluating your decisions? So you can imagine you might have people that are very bad at making decisions, but they know they're bad. Or you might have people who are very good at making decisions, but they're not able to recognise the times they make mistakes.
Katie - Does that distinction relate in any way to someone making the right decision? I'm wondering if being more confident in your decision making makes you more or less likely to actually make the right choice?
Dan - Again, confidence has many different functions, but I think for you as an individual, the danger of having too high confidence is that you're not going to seek dis-confirming evidence. You're not going to go out and test your hypothesis about the world extensively, because you already believe it to be right. So there can be a sense in which over time, having a miscalibrated sense of confidence is gonna lead you to have more extreme beliefs if you like.
Katie - Do you think there's any sort of interesting social reflections there, because we seem to favour confident people, right? Whether it's in the media or perhaps in politics or something.
Dan - It's true for example, in politics. You can say that the general voter tends to prefer confident people. We want to note that those people who are in charge know what they're doing, but that sort of introduces a different incentive scheme, if you like, for confidence. Such that if you're a politician, you might realise that even though you have a doubt about a certain policy or a certain plan for government, then it's going to be in your interest to have overconfidence in that policy or in that plan. Because you know that that's going to turn into some political currency for you. It just really highlights the social aspect of confidence when you get to this larger political scale.
Katie - Do you think there's anything interesting to say about confidence in decision making and the scientific method?
Dan - Absolutely, because I think confidence in decision making, it's about evaluating the strength of your belief about some hypothesis that you base your decisions on. And what we do in science is that we have hypotheses. We go out to do experiments to test the strength of our belief in those hypotheses. Now you could say that the scientific method is implicitly informed by what we know about biases in confidence in decision making. So we know we have this confirmation bias. We know that there are other factors such as the appealingness, the simplicity of our hypothesis that might sway us in that direction. So we think of experiments, we think of statistical tests that are going to allow us to control for those biases that might drive confidence in decision making and everyday life.