Dr. Tomás Lejarraga: How Birth Order Influences Risk Taking Among Siblings

Show Notes for Episode #2 of Unraveling Behavior

In this episode, I am joined by Dr. Tomás Lejarraga, a behavioral scientist working at the intersection of economics and psychology. We explore how birth order influences siblings' willingness to take risks. Our discussion begins by examining the long-held hypothesis that younger, laterborn children are more prone to taking risks than their older siblings. Dr. Lejarraga shares insights from a study on risk-taking behavior in adulthood, revealing surprising findings that challenge this belief. We also discuss a second study suggesting that while birth order effects cannot be entirely dismissed, they are primarily observable in younger ages and may not persist throughout life. Additionally, we delve into the various methods scientists use to assess individuals' willingness to take risks, the competitive dynamics among siblings, the implications of null results, and the influence of environment and culture on birth order effects. The episode will help listeners understand the complexities of sibling differences and how family environments shape our behavior.

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Links 

• Connect with Dr. Tomás Lejarraga and explore his work: Homepage, Google Scholar
• The scientific studies discussed in this episode: Lejarraga et al. (2019); Lejarraga et al. (2024)
• Other scientific studies mentioned: Arslan et al. (2020); Frey et al. (2017); Rohrer et al. (2017); Sulloway & Zweigenhaft (2010)
• German Socioeconomic Panel

Timestamps

• 01:33 How risk preferences form and develop
• 03:37 Family dynamics and their impact on personality traits and risk taking
• 08:42 Defining laterborns
• 10:40 Past research on birth order effects on personality and risk taking
• 16:25 Methodology used to study birth order effects in adulthood
• 19:51 Self-reported risk taking and exploring personal assessments
• 26:01 Lab experiments and analyzing risky choices in controlled settings
• 30:49 Real-life risks and the choices of notable explorers and revolutionaries
• 33:47 Interpreting null results and what they mean for birth order research
• 36:20 Could birth order effects be confined to family environments?
• 39:27 Investigating birth-order effects across different age groups
• 45:18 Parental strategies on whether to counteract or embrace the influence of birth order
• 48:09 Focus on Western samples in birth order research and the need for cross-cultural studies
• 50:13 Understanding common perceptions about birth order effects
• 51:25 Learning pathways with instruction vs. experience depending on birth order
• 53:10 The environment's influence in shaping risk-taking behavior

Transcript (edited)

Sofia Morais: I’m very honored to have you on the podcast.

Tomás Lejarraga: Thank you for having me, Sofia.

Sofia Morais: To kick things off, what drew you to study the link between birth order and risk taking? Was there a specific moment or a scientific finding that really sparked your interest?

Tomás Lejarraga: Well, I’m generally interested in how people make decisions under risk and under uncertainty. And so one question you can ask is: Is there such a thing as a “risk preference” and, if there is, where does it come from? And so, at the time when I was considering these questions, there was a study that came out by Renato Frey and other people at the University of Basel and the Institute here, the Max Planck Institute for Human Development, in which they had studied risk taking exhaustively. They had a very large sample and they measured risk taking in a variety of ways. And they made several important observations. One of the observations they made is that risk taking has the properties of a personality trait. And so if you’re interested in the origins of risk-taking propensity or risk preference, and risk taking is similar to a personality trait, then you can ask where does personality come from. And part of the answer is hereditary. The other part is from the environment. And the family environment is a good candidate to explain how personality is formed or shaped. At the time, this was what led me to be interested in how birth order influences risk taking.

Sofia Morais: It’s not entirely obvious for the general public, how birth order might actually influence aspects of our personality. I mean, the connection is not entirely obvious. Could you explain the family dynamics, the mechanisms behind why birth order might influence risk taking.

Tomás Lejarraga: Yes. So the family dynamics model, by Frank Sulloway proposes the following: That siblings within the family compete for parental resources, for parental investment, such as, care, attention, love, or even material resources. And so children compete, siblings compete, and they do so, according to the family dynamics model, they do so in a similar way that organisms compete for resources in the natural environment. And, how is this so? Well, the principle that applies to the competition for resources, according to Darwin’s evolutionary theory, is the principle of divergence. So individuals, when they compete for the same resources, they will try to do so by differentiating themselves from one another. And, by doing so, they reduce rivalry. And so according to the family dynamics model, children within the family compete for parental resources. According to the principle of divergence, they will differentiate themselves from one another gradually, occupying different niches within the family. For example, one of the siblings may compete for academic achievement and gradually become the smart one. And another sibling, to reduce direct competition, may choose or deploy a different strategy—may become the entertainer, for example. And maybe another sibling may find that those two niches are occupied and then explore, perhaps rebel, become the rebel of the family. And so the idea is that growing up under these family dynamics, slowly and gradually, shapes personality. This is the idea of the family dynamics model.

Sofia Morais: And what role does risk taking play in these dynamics?

Tomás Lejarraga: The idea is that firstborns enjoy a time alone with his or her parents, and have easy access to parental resources, have no competition. And so when, when another sibling comes along, another sibling enters a family, there is competition for resources. So the firstborn will tend to develop strategies that would be directed at securing the status quo. Strategies that safeguard the resources that this sibling already controls. Also, the firstborn is physically and intellectually more developed than the laterborn. When the laterborn comes along, and that niche is occupied, this secondborn will have to explore alternative ways of acquiring parental resources. And through this exploration, this secondborn will be more inclined to take risks.

Sofia Morais: If I understand you correctly, the hypothesis that one can derive from this model is that laterborns will tend to take more risk, be inclined to take more risks, than their older siblings.

Tomás Lejarraga: Yes, that’s the hypothesis. Firstborns tend to develop more conservative strategies, and laterborns tend to develop riskier strategies. And the more competition there is, the more it pays off to take risks, according to the family dynamics model.

Sofia Morais: To clarify the terms before we proceed: We’ve been talking about “laterborns”. We haven’t said lastborns. So my question for you is: Who are considered to be the laterborns? Could you clarify the use of the term laterborn?

Tomás Lejarraga: The way I’m using it now and I’ve used it in my work, laterborns are non-firstborns. We draw the distinction between being the first sibling in the family compared to any sibling that comes afterwards.

Sofia Morais: In the context of this model, are there any specific predictions about the role of middleborns?

Tomás Lejarraga: Yes, according to Sulloway, middleborns are special. As I said in the beginning, the strategies that siblings deploy to compete depend on parental investment. And there’s evidence that shows that middleborns receive fewer parental resources compared to firstborns or lastborns. Middleborns face slightly more scarce resources than their first- and lastborn counterparts. So they are expected to be slightly more prone or particularly more prone to taking risks.

Sofia Morais: In your work, you treat middleborns and lastborns within the same category and you call them “laterborns”, right? So that’s how we will use the term for the rest of our conversation.

Tomás Lejarraga: Yes.

Sofia Morais: Let’s turn our attention to the study that you coauthored with Renato Frey, Daniel Schnitzlein, and Ralph Hertwig, which was published in the Proceedings of the National Academy of Sciences in 2019. When you started this project, what was the state of the evidence concerning the effects of birth order on personality and risk taking?

Tomás Lejarraga: There was an interest in birth order effects on personality. There was a long tradition of looking at how birth order influences personality. But at the time, in 2019, there had been a series of articles that had shown that birth order effects on a variety of personality traits were nonexistent. There were no birth order effects on personality traits and a very small effect on intelligence, with firstborns scoring only slightly higher than laterborns on intelligence. But according to the authors of that paper, the effect was so small that we should not pay attention to it. So this was the growing consensus for personality traits.

Sofia Morais: And that was about 2015, if I’m not mistaken.

Tomás Lejarraga: 2015, 2016, yes.

Sofia Morais: But this was already contradicting earlier evidence.

Tomás Lejarraga: Yes, the early evidence showed support for the family dynamics model. The growing consensus around 2015 emerged after addressing a number of methodological weaknesses that were present in previous studies. And the new evidence pointed in the direction of no effects on personality traits. This was the consensus in 2015, with respect to personality traits, generally. With respect to risk taking, the evidence was mixed. There was one article that had shown in a meta-analysis, an analysis of several articles published, that laterborns tend to choose sports that were considered riskier than firstborns. And this study also showed that if you take siblings that play baseball, laterborns tend to play the game in a riskier way.

Sofia Morais: And this is real data.

Tomás Lejarraga: This is real data. And so, there is this evidence favoring birth order effects on risk taking, in line with the family dynamics model, with laterborns taking more risk than firstborns. And there was another study, mostly based on personality traits, that also included a measure of risk taking. And this other study, based on a very large sample, found no birth order effect on a measure of risk taking that was self-reported. So in this study, people report how much of a risk taker they think they are. They answer a question, on a scale from 0 to 10. And so the evidence was mixed. One study showing strong support for the family dynamics model, the other study showing no support and using different measures, suggesting that perhaps the measure has an influence on whether we observe birth order effects or not.

Sofia Morais: In one case you have actual choice, of sports, right? And in the other case, you have answers to questions.

Tomás Lejarraga: To a question, yeah.

Sofia Morais: These mixed findings provided the starting point for your study. And what I would like to ask you is: Were you, from the beginning, committed to a certain outcome? Did you have an expectation about what you were going to find?

Tomás Lejarraga: For us, it was more of an open question because there were results coming from the meta-analysis clearly showing birth order effects for risk taking, and there were other results that were inconsistent. So, it was more of an open question. And so we tried to address the problem in the best way we could to see what the data was going to say about that question.

Sofia Morais: You didn’t have a specific intuition as to whether you would observe an effect or not?

Tomás Lejarraga: Well, there was a strong tradition of birth order effects. So I think even though it was an open question, there was some expectation that we would observe birth order effects.

Sofia Morais: Could you walk us through the methodological approach that you used in the study, and also define the different measures of risk taking that you used? And I’ll suggest that we define them briefly and then go more into detail later.

Tomás Lejarraga: One strength of this research is that we looked at three different sources of data. We looked at a large survey in Germany, we also looked at data from the Basel-Berlin Risk Study that used a variety of up to 39 measures of risk taking, including behavioral measures. And that means, we will go into detail later, but these were choices with monetary consequences for the participants. And then we also looked at real life choices of risky activities.

Sofia Morais: And the third measure was?

Tomás Lejarraga: So those three: (1) survey data, the several answers that were self-reports; (2) the Basel-Berlin risk study that included self-report measures, but also behavioral measures; (3) and data from risky real-life activities.

Sofia Morais: And these were adult samples?

Tomás Lejarraga: These were adult samples.

Sofia Morais: Your analysis used, besides these measures of risk taking, an indicator of whether an individual is a firstborn or a laterborn.

Tomás Lejarraga: Exactly. For each data, we knew whether the respondent or the participant was a firstborn or a laterborn.

Sofia Morais: And were there any other variables that you also entered in your analysis?

Tomás Lejarraga: Yes. And this is important because we had important control variables such as age, gender, socioeconomic status of the family... We had an important variable, which is the sibship size, the number of siblings within the family, and other variables as well, such as the spacing between siblings, and so on.

Sofia Morais: And were you comparing siblings within families or across families?

Tomás Lejarraga: In the survey, we did both between and within family analyses. For the Berlin-Basel Risk Study, these were between family analyses. And for the study of real-life risky activities, it was between families.

Sofia Morais: Let’s then talk about the first class of measures: the self-reports that came from the surveys. What sort of questions were used to elicit individuals’ own assessment of their propensity to take risks?

Tomás Lejarraga: This data came from the German Socioeconomic Panel. This is a very large survey in Germany, household survey in Germany, with a long tradition. And, in this survey, many questions are asked, of course. The question we used asks the respondent how much of a risk taker the person is. I think the exact wording is: “How do you see yourself? Are you generally a person who avoids risks or do you like to take risks?” And then respondents use a scale that goes from zero, that is labeled as “risk averse”, to ten, that is labeled as “fully prepared to take risks.” And so participants tick some point in that scale. And this was the general risk item. There were also self-reports about risk in particular domains of life, such as risk regarding financial activities, driving, leisure activities, and social activities.

Sofia Morais: And health as well, right? It’s also health.

Tomás Lejarraga: And this is the data... And, of course, we knew whether the person was a firstborn or a laterborn.

Sofia Morais: And did you also, I know there are some studies that have done this, did you also assess the frequency with which people engage in certain risky activities, like how many cigarettes per day they smoke, for instance?

Tomás Lejarraga: Yes, this was part of the Basel-Berlin Risk Study. There some questions were directed at, getting at the frequency of engaging in risky activities, such as smoking, gambling, encounter with risky activities in general. Yeah, so there were frequency measures that were... Essentially asked: In the last 12 months, how many times did you engage in a risky activity?

Sofia Morais: Now, this is very rich dataset because we’ve called them like self-reports, we’ve call them survey data, but even within this category you have a variety of answers, right? You mentioned the general risk-taking question, assessing risks in specific domains of life, and then the frequency with which people engage in different risky activities. So this is a very rich data set. I’m very curious. What did the responses reveal?

Tomás Lejarraga: We observed no differences in the answers between firstborns and laterborns. There was no difference in risk taking between firstborns and laterborns. We found no birth order effects on risk taking.

Sofia Morais: For none of these questions that you just described?

Tomás Lejarraga: No.

Sofia Morais: People might say, “Well, these are just questions, people can answer whatever they like.” Could it be that you didn’t find birth order effects because people didn’t answer accurately? Do scientists know how people address these types of questions?

Tomás Lejarraga: That’s possible. We know that some people find answering these questions difficult. We know that responses tend to avoid extremes, maybe cluster at the middle. Even so, for example, the general risk item from the German Socioeconomic Panel has been shown to be a very good and reliable measure of risk taking. It gives us a signal. Maybe it is not a perfect measurement, but it carries information.

Sofia Morais: Have scientists ever asked people what they are thinking when they answer these questions? How do they come up with a number?

Tomás Lejarraga: One reason why this measure is useful and reliable is because, apparently, what people do to answer these questions is look into their memory and, essentially, retrieve the instances of their previous risk-taking activities, and report based on that information. And that makes the measure relatively stable because those memories are unlikely to change drastically from one year to another. This recent study, conducted by people from this institute, was very interesting in exploring why such a simple measure can be so useful.

Sofia Morais: It draws on people’s experiences, right?

Tomás Lejarraga: Exactly, yes.

Sofia Morais: Let’s now turn to the second class of measures: The actual choices that people make in lab experiments. I’d like to ask you how to these experiments work and what they reveal about risk taking.

Tomás Lejarraga: These experiments were conducted in the Basel-Berlin Risk Study. The authors of that study tried to measure risk taking in the most encompassing way that was possible at the time. It was the largest study known to me, at the time. And so they used a variety of measures of risk taking that were validated, and that were used by other researchers. The measures had a tradition. And so these were known, well-validated measures of risk taking. To give you an example, one of them is the balloon analog risk task. This is a task in which the participant sits in front of the computer screen and sees a balloon. By clicking on a button, the balloon inflates. The more the participant inflates the balloon, the more money accumulates in a temporary account. And whenever the participant wants to stop, can stop, and cash the money he has accumulated by clicking. The thing is, the more you click, the more likely it is that the balloon bursts. And if the balloon explodes, the participant loses the money…

Sofia Morais: Sounds like fun.

Tomás Lejarraga: … that accumulated in the temporary account. The point is that the more a person inflates the balloon, the greater their risk-taking propensity is revealed. This is one task. Other tasks involved choosing between gambles. For example: Do you prefer €3 for sure, or do you prefer to play a gamble in which you might win €4 with 80% chance or nothing otherwise? And so participants would choose. If they chose three, they were paid €3, but if they chose the gamble, a gamble was played. And if the if the outcome of the gamble was four, then this person would take €4 home or if it was zero this person would not get anything. What is interesting about these measures of risk taking is that they have consequences. Participants do not just answer questions like in the other study. These are choices with consequences.

Sofia Morais: And just to clarify for our audience: There’s no right or wrong here, right? There are no right or wrong answers. Your performance will determine your payoff when you leave the lab and go home, but this is determined by a chance component and not by the accuracy of your choices, correct?

Tomás Lejarraga: Exactly. This is not about accuracy. It’s about preference.

Sofia Morais: And you examined people’s risky choices in nine experiments that are part of the Basel-Berlin Study. Did laterborns make riskier choices than firstborns?

Tomás Lejarraga: No. Essentially, the answer is no. There was no difference between firstborns and laterborns in those behavioral tasks.

Sofia Morais: In your analysis of the self-reported data and in your analysis of the behavioral measures, you included additional variables. You mentioned age, gender, the number of siblings, the spacing between siblings. Did any of these variables play a role?

Tomás Lejarraga: Essentially, we did not observe any birth order effects in these two studies. So none of these variables were related to whether we would observe birth order effects or not.

Sofia Morais: So overall, we can summarize the result as: Laterborns take as much risk as firstborns in the behavioral measures and report as much willingness to take risks as their older siblings.

Tomás Lejarraga: Yes, in adults.

Sofia Morais: Those are the samples we are talking about. There is still a third measure of risk taking that you used, which concerned risky life choices. You analyzed a data set of historical figures who took significant risks. Who are these individuals?

Tomás Lejarraga: These are famous explorers and revolutionaries. We looked at exploration and joining a revolution, or starting a revolution, as two risky life decisions. We took a bibliometric approach. Instead of choosing which explorers to look at by recalling from memory which explorers are important to look at, what we did was: We took three encyclopedias that listed explorers and then we looked at the explorers that appeared in the three sources. That is, we looked at the intersection of explorers from these three sources. And when we had this subset of explorers that we were going to look at, we started a search of their birth order and their sibship size, i.e., the number of siblings in the family. So we collected these two pieces of data: The number of siblings in the family and the rank of the person in that sibship. And we did the same analysis for revolutionaries. So, for example, some explorers are... Alexander von Humboldt appears there. And then, Hillary, the first person to summit Everest. Yuri Gagarin, for example. These are among the explorers. And among the revolutionaries we have Rosa Luxemburg, Mao, Che Guevara, Pancho Villa. All very interesting characters. And we had to go into, essentially biographies, and try to get these two pieces of information.

Sofia Morais: And were explorers and revolutionaries more likely to be laterborns than firstborns?

Tomás Lejarraga: What we observed was that explorers and revolutionaries are not more likely to be laterborns. They showed the birth rank that you would expect if there are no birth order effects. So, overall, we didn’t observe birth order effects across the three analyses that we conducted.

Sofia Morais: At this point perhaps our audience will start wondering... Here we have a podcast episode that so far has only covered null results. I think it might be a good moment to explain why null results are so important in scientific research.

Tomás Lejarraga: This is a good question. Results, whether they are null or not, they never stand alone, I think. They always speak to our expectations. Whether a result is interesting or has more or less scientific value depends on how it aligns with the expectations. So I often tell my students, if you go out and take a representative sample of world population and you measure heights and you observe that men are not taller, that there’s no significant difference between men and women, or men’s and women’s heights, then this is a very interesting outcome because the expectation is that men are taller than women. There you have a null result that may lead you to reconsider the selection pressures on physiological development, for example. And so, in the context of birth order effects, as I said in the beginning, for us, the question was a little bit open. But there was interest in the community due to a tradition of birth order effects, of effects for which there was evidence… The more recent consensus was, however, that those effects were nonexistent. So when we conducted this study, there were high expectations about what we were going to observe. And so we observe a pattern of results that speaks in favor for no birth order effects. But again, we’re looking at an adult sample.

Sofia Morais: So when you find mostly null results with no significant effects, this triggered a deeper inquiry. How did you proceed from there?

Tomás Lejarraga: One question you can ask is, after you see no birth order effects, is why some people do, why some studies show birth order effects on risk taking and why didn’t we.

Sofia Morais: We were talking about the study on the choice of sports.

Tomás Lejarraga: For example. When you look at that study, the choice of sports was moderated by age, showing stronger effects of birth order on sports choice for younger respondents than for older respondents. So age had something to do with the matter. And so, we hypothesized that, perhaps, what happens is that siblings engage in the family dynamics hypothesized by Sulloway... They behave in accordance to the theory while they are subject to the competitive pressures of their family. But an element of the family dynamics model is that these dynamics shape personality. And since personalities are a relatively stable construct, according to the theory, you should expect to see differences in adulthood. Our hypothesis was that, well, perhaps these dynamics occur in the household, but children don’t carry those strategies once they leave the home environment, and they behave differently in a different environment. And there was some evidence by Harris suggesting this, what we call “context specific learning hypothesis”. What Harris had shown was that children behave differently at home than in school. Reports from parents and reports from teachers tend to differ. So here we have children that are able to adapt their behavior to the particular domain they’re in. Our hypothesis was that, maybe that’s happening for risk taking as well, so that children exhibit birth order effects when they are subject to the family dynamics, but they stop showing those or deploying those strategies when they leave the family environment. And so the hypothesis was, if age is a proxy for whether the respondents are within the family environment or not, then we should expect to see birth effects among young respondents, among children, and expect that those effects start to fade as they transition out of the home, eventually disappearing in adulthood, as we observed in the study that we just discussed.

Sofia Morais: This was the hypothesis that you tested in an article that you published earlier this year, an article you coauthored with Daniel Schnitzlein, Sarah Dahmann, and Ralph Hertwig. And this is a study that was published in the Annals of the New York Academy of Sciences. Could you guide us through the methodological approach that you used in the study?

Tomás Lejarraga: What we did after posing this hypothesis—that birth order effects emerge at home but disappear when siblings transition out of the family environment—is that we went back to the data from the German Socioeconomic Panel, and we looked at whether there was data available for younger cohorts, for respondents that were in an age range that we could consider being at home. And we noticed that this data was available. And so we were able to replicate the original analysis, but for different age samples. We have data for respondents starting at age 13, and then on to several other samples until they match the age of the respondents in the original study. This was one source of data. Maybe I tell you what we observed there, and then we move to the other source of data. What we observed there was that, indeed, birth order effects appeared, as we expected, for the youngest respondents.

Sofia Morais: And these are answers to questions?

Tomás Lejarraga: These are, again, self-reported measures, to the general risk item from the Socioeconomic Panel. So, this was an answer to the question, “How do you see yourself, are you a person that likes to avoid risks or to take risks?” And, by the way, it is important that these are children self-reporting, because there are studies of children, of birth order effects in children, but it’s often the parents judging the risk-taking propensity or the personality of their children. We specifically sought data where the children themselves were providing the answers. Essentially, what we observed was that the effects emerged very clearly in the young samples and disappeared as siblings transitioned out of the home. And for the samples that were as old as the adult sample that we examined before, then the effect disappeared. So essentially, we found support for the context specific learning hypothesis, the idea that there are birth order effects when siblings are in an age that are subject to the family dynamics, but the effects disappear when they are at an age suggestive that they have left the home. That was data from the German Socioeconomic Panel. But we said: Let’s look for some other data to see if we can validate...

Sofia Morais: Thinking that there might also be differences between different data sets or even between countries.

Tomás Lejarraga: Exactly. We looked for a data set that met these criteria that we had: Children in the sample, that it was the children themselves giving the responses, that there were samples of different ages from childhood into adulthood. And we found a longitudinal survey from the United States that met these criteria. And we did the same analysis and observed the same pattern of results. Here the sample started at age 10. And, what we observed was that birth order effects were very clear at young ages and slowly vanished as siblings transitioned out of the home environment.

Sofia Morais: Do these results imply that birth order effects are in some sense a response to children’s current circumstances?

Tomás Lejarraga: Yes. That’s one way of putting it. We observed that children are responding to the competitive dynamics within the home; when competition and rivalry decrease, it no longer pays for laterborns to continue taking risks. So, yes, I think this is evidence for how much the environment influences risk taking.

Sofia Morais: The parents watching or listening to this episode may now be wondering, “But wait, my children have different willingness to take risks and that is because they’re competing for my attention, for my resources?” Could you, Tomás, speculate what you think parents should do in light of these findings? Should they try to counteract birth order effects on risk taking, or should they instead leverage those effects in their children?

Tomás Lejarraga: This is a difficult question that you’re asking me. I think parents cannot make an environment that is equivalent for all their children because there are differences that will always exist. So, for example, when the firstborn comes and joins the family, parents are first-time parents and they have very little experience. They have a lot of time to devote to their firstborn child. And this changes when the secondborn comes along. So now attention is divided. Parents have more experience. Parents are older. It would be very difficult for parents to try to minimize the differences between the environments in which their children grow up. That’s one reason I find it difficult for parents try to undo birth order effects by equalizing the environment. The other idea that comes to mind is that the home is a good environment to learn to compete. And outside the home, there is competition in many domains of life, not in every domain of life, but in many significant domains of life. And so, learning to compete relatively safely at home provides a good learning environment, it’s a kind learning environment. So I think parents do what they can. And I think my suggestion is not to intervene regarding birth order effects.

Sofia Morais: Going back to your research on birth order effects on risk taking, does your work have any methodological limitations that you think our audience should know of?

Tomás Lejarraga: This is a good point. Our research focused mainly, actually it used, a Western sample of respondents. And there is some indication that birth order effects could also be influenced by culture. To have a better understanding of how birth order effects, how birth order influences risk taking and also other personality traits, it’s important to look at different cultures, not only at Western, industrialized, cultures. So that is one of the limitations. And another way to see it is: This is first evidence of the context specific learning hypothesis applied to risk taking. It is interesting to continue to examine this pattern of results and see to what extent it is observed in other samples.

Sofia Morais: Maybe this episode will bring your research to scientists in different cultures and potentially foster collaborations…

Tomás Lejarraga: That would be great.

Sofia Morais: …and create opportunities for looking at cross-cultural differences. Are there still unresolved questions about birth order effects on risk taking that you would be interested in examining in the future, beyond this idea of the cross-cultural comparisons?

Tomás Lejarraga: What we learned in this last maybe eight years studying this problem is that there are strong intuitions in the adult population about birth order effects. Although we observed no birth order effects in adulthood, people have strong intuitions. And this is one reason why these two papers attracted a lot of attention. For many, the observation that there were no birth order effects in adulthood was a bit counterintuitive. By talking to laypeople about our research, we sensed that there are strong intuitions about how birth order influences personality. One aspect of the problem that we would like to document is whether those intuitions indeed exist, whether people do indeed have strong intuitions about birth order effects. That’s one interesting aspect. Another is that this research suggests the extent to which the environment influences behavior, how much the environment influences risk taking. If we think about the environment that the firstborn and the secondborn sibling encounter, it is possible that firstborns and secondborns learn about the world in slightly different ways. Firstborns, because they have their parents' undivided attention, tend to receive more instruction from their parents—this is the hypothesis—while secondborns and laterborns grow up in a home where parents have less time, making them more likely to learn from experience and receive less instruction, at least from their parents. So here we have a possibly distinct way of acquiring knowledge about the world that is a function of birth order. This is another interesting aspect that I think about.

Sofia Morais: Very interesting, I think you should pursue that. To conclude our conversation, Tomás, what impact do you hope to make in your field as you continue to progress in your career?

Tomás Lejarraga: What this research shows and also other research that I have conducted based on how people learn from experience is how much the environment influences the extent to which people take risks. I hope this research contributes to that view, to the view that the environment is critical to how people learn and behave. We often, as we study risk taking, we tend to look at determinants of risk-taking behavior within the mind. And we often do not give enough credit to how much the environment, the structure of the environment, or the conditions in the environment, influence how people behave. I think this work prompts us to consider how much the environment influences siblings’ risk taking. Risk taking is often a response to the learning conditions and to the environments that people find themselves in. That’s the impact I would like this work to have.

Sofia Morais: Tomás, as we conclude, I want to thank you for taking the time to share your expertise. It’s been a pleasure having you. I’d like to wish you all the best for your future research, for your career, and beyond.

Tomás Lejarraga: Thank you very much, Sofia.

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