The Iceberg—Visible and Hidden Identity

When teaching students about identity, we often begin the class with something called the iceberg exercise. Recall that icebergs typically have only a small portion of their mass above the water where it’s visible. The majority of the iceberg, in whatever form it takes, is below the surface of the water and usually out of sight. If you’re trying to navigate around it, you have to make some guesses and just hope you aren’t wrong.

Personal Identity - Understanding Human Identity

Assumptions vs Reality based on Visible Identity

Professor Satterfield Studies Identity
A photograph of Professor Satterfield

So let’s assume I’m an iceberg. You’ve just met me and really only in one professional context. You have some visual information, but what’s below the surface? Come on. Take a chance; start making some guesses. What are your guesses? So what do students say? They start off safe. I’m male. Check. I’m tall. Yes. 6’5”. I’m Caucasian. Well, not entirely true, but mostly true.

Then they start to make some more inferences. I’m not married. Well, there’s no wedding ring, but that doesn’t mean I’m single. They can’t quite place my accent. Some think I come from the Midwest, some from California, some even say New England. All wrong. I was born and raised in Madison, Tennessee, just outside of Nashville. Now they’re starting to get warmed up. They assume I come from a wealthy family. They assume my parents were doctors. They imagine I went to prep school and never had to work during high school. They guess that my first job was in a research lab and my Dad pulled a few strings so that I could get it.

My first job? Bus boy at the Grand Ole Opry, where I had dreams of one day meeting Dolly Parton.

How accurate were they? Terrible. My Dad was an appliance delivery and repair man for Sears, and my Mom worked all sorts of jobs, including babysitting and cashiering at Walmart. Neither were able to go to college. We probably would have been considered middle or even lower middle class. I went to a public high school where almost no one went out of state to college. In fact, when I told my guidance counselor I wanted to go to MIT he replied, “Well, you’ll like Memphis. It’s right nice.” My first job? Bus boy at the Grand Ole Opry, where I had dreams of one day meeting Dolly Parton. Of course, the point being, appearances can be deceiving. People are immensely complicated and interesting. Your job is to learn how to elicit each person’s story and savor it. What’s your story? What’s your identity?

Personal Identity as a Function of Narrative

We’re going to look at identity, social support, socioeconomic status, work stress, and public health. But what are the elements of identity? How do we perceive, change and build identity? How does identity affect our health? What are the pathways? It is certainly partly science, but you’ll learn that it’s both quantitative and qualitative. We need numeric data, but we also need stories. We also need narratives.

Elements or characteristics of identity would include race, ethnicity, gender, age, sexual orientation, physical attributes, personality, political affiliations, religious beliefs, professional identities, and so on.

So let’s think about some of the basics about individual identity. Identity is simply defined as the characteristics determining who or what a person or thing is. So elements or characteristics of identity would include race, ethnicity, gender, age, sexual orientation, physical attributes, personality, political affiliations, religious beliefs, professional identities, and so on. We belong to multiple groups at the same time. We may hold some traits more central to our identity than others, but not everyone holds that same value system. And in fact, what we value the most might change as we grow older. This overlapping, interconnected aspect of identity is called intersectionality, the intersection of those different elements of our identity. It’s important to keep that in mind as we start digging deeper into how identity affects health.

Changing Identities and Identity Development

We know that our identities are somewhat fluid. Although some characteristics are stable, our height, our skin color, maybe even some personality traits, our identity develops over time. There are a number of different identity development stage theories, mostly concerned with race, that range from starting out saying, denial: I’m color blind, color just doesn’t matter; to immersion, I only want to be around people from the same race; to autonomy, and eventually to integration. In short we try to find our tribe while being able to connect with and to understand others.

Teenage Girls Make a Good Study of Identity
Identities develop over time

Our tribe, of course, shares the same cultures. What is a culture? A culture is the collage of language, beliefs, traditions, codes of conduct, rules, membership, health beliefs that guide our daily lives. Our culture influences our tastes, our food choices, sensations of pain and pleasure, and even how we love. Like identity, we can belong to many cultures at the same time, however, we can’t necessarily be competent in all of them. In fact, belonging to a culture doesn’t mean you’re competent or fully understand that particular culture either.

Lest you think that culture and the study of culture is starting to sound awfully squishy, remember that science itself is a shared system of beliefs, practices, norms, expectations, and maybe even a special language, just like any other culture. It’s slippery to grasp because we are so immersed in it or as a student once told me, a fish doesn’t even know it’s wet.

Research on Culture and Identity

I’d like to share some of the research done on culture and how they can substantially, but often implicitly, influence our behaviors. These were cross cultural studies done with U.S. western individuals, compared to Japanese and Korean individuals, with much of this work done by Nisbett and his colleagues.

How Cultures React is an Indication of Identity
Different cultures will respond to the same stimuli with different actions.

In the first study, westerners and Japanese were told to describe a fish tank. So they look at a fish tank, typical fish tank, rectangular, it has water, it has fish, and so on. Folks from the west talked about the biggest fish that was in the fish tank. The Japanese talked about the context. They talked about the bubbles; they talked about the aquatic plants; and they talked about the other fish.

When he looked at parents, he found that western parents, when teaching language to their kids, they tend to teach nouns first. Koreans, however, tend to teach their kids verbs and especially verbs about relationships. If you were to take someone from the U.S. and someone from Japan and show them a cow, chicken, and grass and tell them to make a pair just with two of those, someone from Japan would pair the cow with the grass. It’s about the function. Someone from the West would pair the cow with the chicken. It’s about the noun. It’s about the category. This may seem trivial, but remember that culture permeates every aspect of who we are. It’s how we piece the world together. It’s how we see ourselves, and it’s how we see each other. It also influences how we develop and shape our identity over time.

Categorizing Identity

So let’s look at identity development, and in order for that to develop, we need three things to happen. First we need some sort of categorization; there needs to be a sorting of some sort. We need identification. And we need comparison. So those three elements, categorization, identification, and comparison. Let’s talk about each of those.

…It’s a natural human inclination to make sense of things, to draw connections, to look for relationships. That’s just how we think.

What do I mean by categorization? Much of what I’d like to share is from Sue Estroff and her social medicine colleagues at the University of North Carolina in Chapel Hill. What they tell us is that it’s a natural human inclination to make sense of things, to draw connections, to look for relationships. That’s just how we think. Part of the process is, essentially, sorting people and places into categories that either we or our cultures have created. This seems deceptively simple, and you think it might be a no-brainer, but let me give you a few examples. Let’s say the category dead or alive. Sounds pretty simple, right? Not really. What about someone who is in a coma with little to no brain activity? Are they dead? Are they alive? What about the category of male versus female? Fairly simple, right? Well, again, not really. What about intersex children that are born with ambiguous genitalia? What about racial categories? Now we’re really in trouble. Can you look at a person walking down the street and accurately put them in a racial category? I dare you to try.

Race as a Category Central to Identity

Race and Identity
Race is a classification system used to categorize humans into large and distinct populations

We know that categories are complex, and some of the most complex categories are often central to our identity, but what are they made of; what are they based on? First, let’s look at race. So what is race? It’s defined as a classification system used to categorize humans into large and distinct populations or groups by anatomical, cultural, ethnic, genetic, geographical, historical, linguistic, religious, or social affiliation. Now that’s a mouthful. Essentially, it’s our attempt to categorize or to sort people into categories based on their skin color and based on a very small set of physical characteristics.

There’s currently a raging debate between geneticists and anthropologists about whether or not race is a biological construct.

If we were to ask the U.S. Census, they’d tell us that we have a rather short list of racial categories. The categories are white, black or African American, American Indian or Alaskan Native, Asian, and Native Hawaiian or other Pacific Islander. Latino or Hispanic is not considered a race, but rather an ethnicity, where an ethnicity is more about a shared language or other cultural practices. There’s currently a raging debate between geneticists and anthropologists about whether or not race is a biological construct. Could you look at someone’s genome, for instance, and determine what their race was without looking at where they’re from or looking at their ancestors? Maybe, maybe not. The anthropologists correctly point out that there’s often more genetic variation within one particular race than between the races with African Americans being a prime example, but if race isn’t a biological construct, what is it?

The American Association of Anthropology, the other triple A, has a terrific collection of materials called “About Race” on their website. It helps us understand how these categories got created and some of the ramifications about using these particular categories. Recall our lecture on cognition and the prevalence of self-serving biases. When we make categories, we open the door to making judgments. How we judge depends on how we self-identify. We tend to positively reappraise people who are in our in-group, and we tend to devalue people in another category, people in the out-group. Identification and comparison are the last two aspects of identity development. Let’s turn to them.

Identification and Comparison – How to Identify or Join a Group

How do we identify or join a group? We’ve talked a lot about the biopsychosocial model and its spheres of influence. There’s a similar model, the social-ecological model, that talks more about social spheres of influence. Really, I think about concentric circles where the individuals in the center, their significant other, maybe their family is in the next circle, then their neighbors, their communities, and so on until we get to their political influences, the country, and the globe. All of those influences may be present at any particular time.

Identity Formation
A little boy in the process of identity formation

In fact, the image that comes to mind for me is the image of President Obama and a little African American boy who reaches up to touch his hair to see if their hair is alike. That little boy is in the process of identity formation. He’s looking for similarities; he’s looking for differences, maybe with profound psychological consequences.

But of course, our identity changes over time. Part of young adulthood is striking out on your own, taking your odyssey, and deciding who’s my tribe. So how do we compare in-groups versus out-groups? Of course, we start noticing, how are we similar? How are we different? We start asking others for feedback. We see which tribe opens the door, which tribe closes the door. We begin to shift our thinking. As we are connecting with a particular group of people, we start to minimize our differences; we start to maximize our similarities. Those cognitive distortions start to kick in. Our in-group is terrific. Our tribe is terrific. The out-group is not so great. We make those generalizations.

How Does Identity Affect You?

So how does identity affect you, and how does it affect those around you? Obviously, it will affect your self-concept, your sense of value, your sense of self-esteem. It will also affect your sense of perceived control. Remember, there’s a hierarchy in society, there’s a ladder of power. Where are you on that ladder based on what your identity is? Sometimes you can choose that; sometimes others choose it for you. There’s a number of social responses to your identity, sometimes known, sometimes implicit and unknown.

If you’re someone who happens to be lucky enough to be considered very physically attractive in a particular culture, then you’re going to get a lot of attention and probably a lot of resources and probably a lot more forgiveness than other people might receive.

An example would be unearned privilege, and usually if you’re the one that’s receiving the privilege, you’re not terribly aware of it. If you’re the one seeing other people privileged over you, you’re very much aware of it. For example, if you’re someone who happens to be lucky enough to be considered very physically attractive in a particular culture, then you’re going to get a lot of attention and probably a lot of resources and probably a lot more forgiveness than other people might receive. We’re also talking about being the recipient of stereotypes, potentially the recipients of bias, discrimination, or prejudice. This may be due to either hidden or visible identity. Visible identity would be an individual who is stereotypically African American, their skin color, their hair. Hidden identity might be someone who’s Jewish. People don’t know they’re Jewish unless they say they’re Jewish, but there may be a cost of hiding if we don’t make that hidden identity visible.

Here’s an example. There was a heartbreaking study originally done in the 1960s and then redone just about 10 years or so ago. The experiment went as follows, They recruited a group of young African American girls, usually aged 3, 4, 5, 6 years old. They bring them into the laboratory room. They put two dolls on the table in front of them. One is a white doll, and one is a black doll. The experimenter asked the little girl could you point to the good baby? She points to the white baby. Could you point to the bad baby? She points to the black doll. These little girls have already internalized those stereotypes, presumably not from their families, but from the culture at large.

Identity Experiments – The Robber’s Cave: Phase One

Muzafer Sherif’s ‘Robber’s Cave Experiments’ studied the behavior of pre-teen boys at a summer camp.

Another seminal experiment on in-group, out-group experiences and distortions comes from Muzafer Sherif, a Turkish social psychologist, who in the 1960s did a number of studies at a summer camp. His most famous series of experiments were called The Robber’s Cave Experiments. They were called Robber’s Cave because that was the name of the state park in Oklahoma. What he did was to recruit 11- and 12-year-old preteen boys, and he brought them into this summer camp for free. Like they do in most summer camps, they were divided into groups. He had the Rattlers, and he had the Eagles. In the initial part of the experiment, they were completely separate. He wanted those groups to develop a cohesive identity. He wanted those in-groups to begin to develop. He wanted those cognitive, positive cognitive distortions to begin to develop.

The Robber’s Cave Experiments: Phase Two

Phase two of the experiment, he brings the Rattlers and the Eagles together, but he puts them in opposition to one another. So he has them compete for prizes; He has them compete for resources; and he begins to see what will happen in terms of cognitive distortions between the in-group and between the out-group. You can probably predict what happened. The Rattlers started making all sorts of assumptions about the Eagles. The Eagles started making all sorts of assumptions about the Rattlers. They made all sorts of generalizations, stereotypes. They’re mean. They’re lazy. They’re no good. They always cheat. They don’t care. They’re underhanded. This is exactly what happens in society all the time.

The Robber’s Cave Experiments: Phase Three

So they put the Rattlers and the Eagles together in this shared task. After a number of these shared tasks, guess what happens? The Rattlers start to get to know the Eagles as individuals, as people, and they actually see that they’re fairly similar.

The most interesting part of this experiment, though, was in phase three. In phase three Sherif engineered all sorts of accidents where he needed the boys help so that they would have to work together in order to correct the problem. So an accident would be something like a tree falls across the road, and in order for them to take the bus out of camp, they have to get the tree off the road, but it’s a big tree, and so they need kids with lots of axes to do lots of work and hauling wood away. So they put the Rattlers and the Eagles together in this shared task. After a number of these shared tasks, guess what happens? The Rattlers start to get to know the Eagles as individuals, as people, and they actually see that they’re fairly similar. Those negative cognitive distortions begin to melt away as they start to cohesively bond with one another. They become one big in-group instead of the in-group and the out-group. In fact, this is still taught in business school. If you have two warring tribes of some sort the best thing that you can do to build group cohesion and have good team work is to have them roll up their sleeves and solve a problem together.

Stereotypes, Stigma and Identity

Next I’d like to move to talk about the impact of stereotypes and stigma, and specifically I would like to talk about a phenomenon called Stereotype Threat. Stereotype Threat refers to being at risk of confirming, as a self characteristic, a negative stereotype about one’s group. So let’s say the stereotype is, if you’re African American, then you’re not going to do very good in school. The individual does not have to believe that stereotype at all, but the fact that they know that stereotype is there, when they sit down to take an exam, it may be taking up a little bit of their head space. They may be worried; what if I don’t do well? Or they may be angry. What if they’re thinking, I’m not going to do well? Regardless, it’s taking up a little bit of cognitive resources, and it may actually create a self-fulfilling prophesy. So that’s the theory, but is the theory actually true?

The Math Test – Gender Identity Studies

I wanted to share a number of different studies, and all of these are referenced in your study guide. The first is from Claude Steel at Columbia University. He did a couple of different versions of this. He wasn’t just interested in race; he was also interested in gender. So there is a stereotype that men are better than women in math, so what he did was to bring men and women in, and he gave them a math test. Only in order to activate stereotype threat, he first had them, essentially, pay attention to whether or not they’re a man or they’re a woman. Simple interview, talking about gender, activates that identity element of men or women. Guess what happens? The men did better than the women on the math test. Condition number two, he brings in men and women. He gives them a math test, but he tells them, he doesn’t prime them about gender, and he tells them this is a new kind of math test, and we found that there are no gender differences between men and between women. They take the test. They perform equally. It was exactly the same math test as in the first part of the experiment.

Understanding Identity with The Achievement Test

Next experiment that he does now he is interested in race, and he’s looking at black, white, and he’s interested in achievement test. So again he brings in students. He gives them an achievement test. Either he primes them first to think about the fact that they’re black or they’re white and gives them the test. When their primed, stereotype threat happens, and he sees a difference in terms of the achievement where the white students do better. If they are told that it’s a special test that isn’t sensitive to differences in gender, isn’t sensitive in differences to race, they actually perform at equally the same level.

Couple of different variants of this experiment, and I think this is true, because many people seem not to believe these findings, but it’s been done a number of different ways, so let me give you two more examples. The next is by Ryan Brown and Eric Day. They use something called the Raven’s progressive matrices. Most of you probably haven’t heard of the Raven’s progressive matrices. It’s actually an old IQ test where instead of having verbal-type questions, it shows you pictures. It’s all visual, and it asks you, out of an array of particular choices, to pick the two that match. Starts off fairly easy, you pick the two circles. You pick the two squares. And then, of course, it gets increasingly complicated and difficult. It’s sort of a fun puzzle to do. The point is, most people don’t know about it, it’s not verbal; it’s not about math, so where would the bias be?

Stereotypes and Identity
A test that plays into stereotypes will often see those stereotypes dramatically affect the outcome of that test.

First part of the experiment, what Ryan Brown and Eric Day do, is they tell black and white students that this is about IQ. When they tell the students it’s about IQ, whites do better than blacks. When they’re told that it’s simply a puzzle, blacks and whites do exactly the same. Next variant of the study, and a really interesting wrinkle, was done by Jeff Stone at the University of Arizona. Again, he’s interested in stereotype threat, and again, he’s looking at black and white students, but Jeff Stone is a sports psychologist, so he’s interested in slightly different kinds of stereotypes. So he has black and white students. He didn’t want to pick, say, football or basketball, where there’s lots of different racial stereotypes. He wanted to pick a fairly neutral sport, if we can call it that, putt-putt golf. So he has black and white students come in and play a game of putt-putt golf. In one condition he tells them that it’s a measure of social IQ, and in that condition the blacks do worse. In the next condition, he tells them that it’s a measure of athletic ability, and in that condition the blacks outperform the whites. Of course, the stereotype is that whites are smarter; blacks are more athletic. Stereotype threat seemed to hold true in this particular instance.

The Obama Effect

photograph of Barack Obama, the American President
Barack Obama, the American President

I want to share one more example of an effect called the Obama Effect, and let me say that when I heard this my eyebrows certainly went up. I went to the literature, read the paper, even emailed the author to make sure that I was understanding the phenomenon that was at hand. I don’t know if the study has been repeated. I hope it has. This was done right around the time of the first time that Obama was elected as president. This was done by Ray Friedman at Vanderbilt University, and the first version was published in a paper, in the Journal of Experimental Psychology in 2009. He called it the Obama Effect. What was it?

He recruited 500 students, again, these were black and white students. He created a 20-item test, mostly about verbal IQ types of items. Before the Obama election, he found the usual performance gap where the white students were outperforming black students. In fact, the difference was about 30 percent. After the election of Obama, he gave another group of students the exact same test, and there were no racial differences whatsoever. It really makes you think, and it really makes you want a replication. But it’s also exciting to think, are there big environmental events that can reach into our psyches and change those stereotypes? And if they do change those stereotypes, do they stay changed and how long? Is there some sort of engineering, some sort of resilience factor that we can build in? Maybe.

Let’s go back and look at some of those cognitive errors. And remember they’re neither good nor bad, but they have consequences. They’re there for a reason, for a function, and sometimes we use them too much, or sometimes we use them too little. So the first cognitive shortcut that we use is, of course, generalizations. And generalizations aren’t necessarily bad; we do them all the time. We look for patterns. We’re trying to save mental processing energy. This is all about that system-one thinking that we’ve talked about before. It’s efficient. It helps us see connections. The second is about positive, or optimistic, bias. Most of us have a self-serving bias where we pretty much see ourselves above average in all sorts of different things. This is probably our psychological defense mechanisms. Of course, if used too much, then we have an unrealistic sense of who we are, what we’re able to accomplish, and maybe don’t see our weaknesses or work to improve ourselves. It does build pride. It gives us a sense of belonging and self-esteem, but it may come at a cost if used too much.

Devaluation of the Out-Group

Another common cognitive bias is the devaluation of the out-group. This happens all the time. We increase our opinions of our in-group. We decrease our opinions and maybe even dehumanize individuals in an out-group. This probably eases guilt from competition between those two groups. In fact, it makes me think about the labels and frames that we use and how they may subtly or not so subtly affect our opinions, our judgments, our generalizations about others. The study that comes to mind is a classic study that was done by van Ryn. And this was a study looking at the impact of racial identifiers at the top of someone’s medical chart. So this is the way it went. In this particular experiment, van Ryn wrote a paragraph description of a patient. So it would be something like, a 45-year-old Caucasian male presents with left-sided chest pain and on, and on, and on, and on. That was given to one group. And the next group got, a 45-year-old male—no race—presents with left-sided chest pain. He then asked those healthcare professionals a number of different questions. What do you think caused the problem? What level of adherence do you think this patient will have? Do you think he’s going to be difficult or easy to get along with? And guess what? If there was a minority racial label at the beginning of that chart, those healthcare professionals made all sorts of negative reactions. This is why now it’s fairly standard, at least in the ID tag of a case, we don’t put the race. Not because race isn’t important, but because oftentimes, unfortunately in our society, that label is a negative label, and it influences that health professional’s judgment.

Another example, in 1995, the Metropolitan Museum of Art had an exhibit that they called Rembrandt/Not Rembrandt. So there were a lot of fake Rembrandts, many of which, I thought, were incredibly beautiful, but one was real, and one wasn’t. If you bring in a group of individuals and you say this is the real one, this is not the real one, could you rate the quality of them? Guess what? Everyone rates the real Rembrandt as much more beautiful. If you actually switch them so that you tell them the real Rembrandt is fake and the fake Rembrandt is real, guess what? People think the fake ones are now much more beautiful than the real ones, but this isn’t just about subjective opinion. They’ve actually shown these same pictures to people while they’re in a functional MRI machine, and you see when people look at fakes, different parts of their brain light up.

Napa Valley

Expensive Wines Taste Better Experiments
People always believe expensive wine tastes better than cheaper wine.

Next example, this happens in Napa Valley all the time. Whenever I go up there and bring friends there, we do this same wine trick at different wineries. They’ll bring out two bottles of wine. One is a very expensive bottle of wine; one is a very cheap bottle of wine. They’ll take the labels off. They’ll pour two wine glasses. They will tell the person, this is the cheap one, this is the expensive one, which do you like better? Guess what? People always believe the expensive one tastes better, even though we’ve switched those wines so the cheap bottle is actually the one that they’re saying tastes better. You can manipulate those judgments fairly easily, because in our culture, money equals value. If it costs more, it must be better. Right?

But what about those labels that we put on people? You label someone as old or young. You label someone as black or white. You label someone as male or female. What are the consequences, and what can we do about it? Well, we can’t get away from cognitive biases and system-one thinking, but we can be explicit and open in reflecting about our identities and the groups that we belong to. We can be careful when we’re evaluating ourselves, and particularly careful when we’re evaluating our out-group. It’s critical that we leave our comfort zones and interact with people that maybe we’re not so drawn to, so that we get to know them as an individual and not as a generalization or a stereotype.

We teach our students the work of William Carlos Williams, who is a physician and also a poet. He tells us to find the poem in every person. Find their music. Listen for their music. Know yourself. Get to know others. We’re not color blind. We all have identities, and we all have biases, or as a mentor once told me, find your enemies and take them to lunch.

We know that diversity in all its many different forms can be vexing, but it can also be quite valuable, and this isn’t coming from an ideological perspective. I’m just talking about the different perspectives, the different ways of thinking, the different life histories. When combined together, we may often see things that we wouldn’t have seen if we only hung around people that are similar to us. In fact, the National Institutes of Health has been pushing a program called Team Scientist, where biologists aren’t just working with biologists, they’re working with psychologists, and sociologists, and many different disciplines, because each bring a particular lens to the question at hand, and that level of diversity helps us find better answers.

Let’s link identity to health, and specifically, to health disparities. And I’m thinking of the 2002 Institute of Medicine report called Unequal Treatment that distinguishes between health disparities, differences in the prevalence or outcomes of disease, and healthcare disparities, or when care is unequally provided to two people even though they have the same disease. Why do these occur? We’ve covered some of these statistics about health disparities with cancer and heart disease. We know that the life expectancy for a black man in the United States is about the same as a poor farmer in Bangladesh. What’s going on? We should be thinking about chronic stress, cardiovascular reactivity, allostatic load, or what Geronimus has called, weathering. We also need to think about those social factors, use that biopsychosocial model, but what about healthcare disparities? Most people that go into medicine or healthcare want to help other people. They don’t want to provide unequal care. It’s about implicit biases and how implicit biases can sometimes be made manifest, particularly if you’re tired, or you’re rushed, or you’re multitasking. So what do we find when we try to measure implicit bias? Well, we find that we all have biases regardless of our background, our race, our gender, our color. Our task is to be aware of them and do what we can to change them.

I’m reminded of the book Outliers by Malcolm Gladwell, who also reminds us it’s not just about implicit biases; it may be about societal biases as well. He noticed an interesting phenomenon that all of the Stanley Cup players, hockey superstars, tended to be born in January, February, or March. Why is that? Is it biology? Is it genetics? Probably not. It’s about how kids are recruited into hockey leagues. To get in the 5-year-old hockey league you have to be born in that particular calendar year. A kid born in January competes with a kid born in December, and when you’re 5-years-old, that makes a huge amount difference. So the kids born in January, February, and March, they make the cut, and the others don’t. It’s like the Matthew Effect, the rich get richer. So we have a number of models to remember: the biopsychosocial model, the life course developmental model—these things change over time, especially our identities—and the social-ecological model.

From the lecture series Mind-Body Medicine: The New Science of Optimal Health
Taught by Professor Jason M. Satterfield, University of California, San Francisco