#3: What twins studies tell us about self-motivation
Nature + nurture + common-sense tips
TL;DR
Intrinsic motivation differs from one child to another. According to twins studies, the difference is partly down to genes and largely to individual environments.
Genes aren’t fortune tellers: just because you have a certain genetic background doesn’t mean you’ll come out a certain way.
Responding to each child’s interests and abilities is one key to help nurture motivation.
I did not expect that having twins would help me chill out as a mother. Sure, when the ob/gyn announced that we were going from one child to three, my anxiety initially went through the roof. But now that they’re here, some of the mum-guilt has evaporated.
With our eldest, I read all the parenting books, tried to do everything just so, and often felt responsible if something didn’t quite pan out. Now, seeing his twin sisters grow up side by side helps me to relax about the extent of my parental influence.
For instance: we offer them the same foods, at the same times of the day, sitting at similar high chairs. One baby would be content living off nothing but milk and grapes, while the other wolfs down everything on her plate. I don’t blame myself for raising a raisin fiend, just like I don’t take credit for her sister being an adventurous, voracious eater.
That doesn’t mean I will start offering them junk food at every meal; I still take my role seriously and try to do my best. I just stress less about it, and delight in getting to know them and their individual quirks.
Twin drives
Like my kids’ appetites, intrinsic motivation often varies between siblings.
I asked Charlie Chamberlain, a twin mother and research funding consultant in Norwich, UK, about the differences she observes in the motivation of her 6-year-old boy and girl. She says her son will often develop deep passions (“at the moment, he’s really into Russian history”) and set himself elaborate challenges. Meanwhile, his sister tends to “dip in and out of things”.
On the other hand, Chamberlain’s daughter will doggedly practice physical skills, while her son “just doesn’t bother” with a physical skill if he doesn’t find it easy straight away.
Of course, our families are anecdotal, miniature samples. Some researchers use data from hundreds or thousands of twins to tease out the role of genetics and the environment in certain human traits or behaviours, including motivation. In particular, the classical twin study design compares groups of monozygotic twins (who have mostly the same genes, because they come from the same egg and sperm) with dizygotic twins like Chamberlain’s and mine (siblings that just happened to share a womb).
Decades of twin research have shown that “nearly every aspect of human individual differences”—risk tolerance, physical health, income, etc. etc.— is partly heritable1: a mix of nature and nurture.
“Twins studies are not just for twins. They’re a model” that helps understand the general population, says Nancy Segal, a professor of psychology at the California State University-Fullerton.
But if we already know that genetics play a role in pretty much everything, why does this kind of research still matter?
“To be able to intervene, we need first to understand the origins [of certain traits], and the complex interplay of all these origins,” says Margherita Malanchini, a developmental psychologist at Queen Mary University of London.2
Focus on motivation
Some researchers have used twin data to understand why children differ in their motivation to learn at school. This includes a 2015 study led by Yulia Kovas, a professor of genetics and psychology at Goldsmiths University in London, United Kingdom, using data from about 13,000 twins in six countries3.
It found that genetic factors explained about 40% of the difference in academic motivation between children. Neither trivial, nor huge.
The remaining 60% were down largely to children’s individual perceptions and experiences, like a specific peer group or teacher, rather than shared environmental factors like their family’s socio-economic status.
In a later study, Malanchini (who did her PhD under Kovas’s supervision) used the same twins sample to search for the chicken and egg between reading motivation and reading achievement in school, for children between 9-10 years old and 12. Are children interested in reading because they’re good at it, or vice versa?
Malanchini found that the relationship goes both ways.
“The two influence each other pretty much to the same extent. We didn’t expect that,” she says. Previous studies in younger children had found that reading achievement tends to drive motivation rather than the other way around.4
Both of Chamberlain’s kids are keen on reading; her son started recognising written words before he turned two. (“Yellow Submarine!”, he’d say, pointing at the—unillustrated—sheet music of the songs his mum played on the piano.) “He quickly got pleasure from recognising words and taught himself a lot just by staring at books for a long time. I did all the same things with his sister, but it wasn’t until she started school that she picked up reading at about the same pace as her peers.”
“When I see [their motivation], I think, Where does that come from? I don’t want to kill that off,” Chamberlain says. “I think if you know for yourself what you want to be, what you want to do, that’s worth so much.”
Here are Malanchini's (*) and Segal’s (^) suggestions.
Follow their cues
“Really listen to every child and to what they might want and need.” *
“How do I tailor my treatment to each child? That’s the take-home message, for twins and non-twins. Try and be attuned to children’s interests and abilities, and to nurture them.” ^
Don’t expect the same from everyone
“For some children it’s easier to be motivated than for others, and it’s not because they are lazy or unwilling.” *
“We want everybody to be able to reach their full potential.” *
Your role does matter
“Heritability doesn’t mean destiny. Most traits are to some extent heritable, but this doesn't mean that we can’t intervene […]. For example, myopia might be nearly 100% heritable, but you can use eyeglasses.” *
Provide rich experiences outside the home, too
“I don’t mean to dump as many activities as possible on children! For some children, it might be just one thing, while other children will need more stimulation.” *
Watch this space
“We need more research to know what environmental factors can support the development of non-cognitive skills [like motivation]. We’ll have more clear-cut answers in the future.” *
Bonus ideas
Nancy Segal’s latest book: Deliberately Divided. Inside the Controversial Study of Twins and Triplets Adopted Apart, was published just a few days ago by Rowman & Littlefield.
If you find twins studies fascinating, you’ll love the documentary Three Identical Strangers. I won’t spoil it for you—trust me and watch it.
Segal and Malanchini are both speaking at the International Congress on Twin Studies, an academic conference taking place right now and until 14 November 2021 in Budapest, Hungary (and online).
Harden, K.P., Koellinger, P.D. Using genetics for social science. Nat Hum Behav 4, 567–576 (2020).
In this detailed review article, Koellinger and Harden (the author of the recent book The Genetic Lottery: Why DNA Matters for Social Equality) write about using modern genetics for stronger social science, and ultimately for a fairer society:
- “the current workhorses of statistical genetics […] are useful for social scientists whose primary interests lie in understanding effects of environments, such as parenting, policies, or interventions, that might lead to or entrench inequalities.”
- “the realization that success in life is partly the result of a genetic lottery raises new questions not only about underlying mechanisms, but also about fairness and what a desirable distribution of wealth in a society should look like.”
Not everyone loves twin research and behaviour genetics. Some critics say twin studies are crude; they question the assumption that mono- and dizygotic twins are raised in “equal environments”, point out that monozygotic twins don’t have exactly the same genes.
Others worry that adding statistical genetics to the social scientists’ toolbox is a slippery slope that can be used to justify eugenist or racist ideas. To which Malanchini says: “I’m very aware of the bad history that genetic research has, and I think this encourages us to be even more careful in how we conduct studies and interpret our results.”
The sample included twins aged 9 to 16 years old, from registries in Canada, Germany, Japan, Russia, the United Kingdom, and the United States. (The estimates were consistent across different school subjects, ages, and cultures.)
One possible reason, Malanchini says, is that measures of motivation rely on imperfect self-reports, and younger children may not assess their motivation as accurately as older children.
**I’ve updated these footnotes on 12 November 2021 at 8pm CET to add a reference to Harden’s book, and quotes from her review article with Koellinger.**
**I’ve added the twins’ photo on 19 November 2021 at 1pm CET.**