In a recent interview of
David Brooks by Charlie Rose, Brooks recounts experiments done by
Walter Mischel. Mischel, starting several decades ago, presented 3- and 4-year old kids with the choice of eating a marshmallow now or receiving another one 10 minutes later if they could resist eating that marshmallow in front of them. Mischel noticed by following these kids as they grew up that those who resisted the temptation of instant gratification were more likely to be successful later on. He posits that there might be something genetic going on. It certainly has some deterministic overtones if we can predict a person’s life success based on their consumption of a marshmallow when they weren’t even in kindergarten. And it is bothersome that other factors don’t seem to have an impact even though Mischel is cited in a
New Yorker article as saying that
“In general, trying to separate nature and nurture makes about as much sense as trying to separate personality and situation. [...] The two influences are completely interrelated.”
Is this experiment valid? Can we really conclude from it that kids who have mastered self-control at age 4 will be more successful?
Considering the validity of research within psychology, I usually look at three things:
- Sample size
- Length of study
- Presence of a control group
Exploratory research often has small sample sizes. We can make some inferences based on that research but they are on shaky ground. What holds for 20 people might not hold for 1000s. I suspect that the sample sizes in these experiments were small.
Study length varies from point-in-time to longitudinal, sometimes over decades. As Bella DePaulo has pointed out eloquently, using point-in-time studies for psychological research doesn’t give us results to stand on. Mischel’s study is clearly longitudinal, which gives it more credibility.
I think Mischel’s study falls apart with the lack of control groups. Control groups are important if we want to ensure that there aren’t other variables that might be impacting the outcome – suggesting that what we think is the cause (self-control) is really just another symptom of something else. It is plausible that the same environmental factors that increased the self-control in 4-year olds also contributed to their increased success. Maybe they had more involved parents; maybe they had access to better education. Or maybe – something suggested by the researchers themselves – these kids had developed skills that helped them distract themselves from the marshmallow. That might not have anything to do with self-control. It could simply be cunning calculation: Two marshmallows are better than one, after all.
There certainly is something to be said for self-control but I caution to jump to conclusions based on these experiments. Clearly, they are not investigating systemic impacts but are solely looking at personal responsibility.
Addendum:A new British report on health inequalities also seems to underscore factors beyond genes in things like health inequalities. As the latest Too Much newsletter summarizes:
But British health inequalities go far beyond this contrast between rich and poor. The rich live longer and healthier lives than the near rich, the near rich longer and healthier than the middle-income. Health in the UK follows, in other words, a “social gradient.” The lower a person’s social status, the worse a person’s health.
[...]
We typically blame poor health on unhealthy behaviors. Or bad genes. Or a lack of access to health care. None of these factors, as important as they may be, turn out to statistically explain why some among us live lives so much longer and healthier than others. What does?
Says the Marmot Review: “Social and economic differences in health status reflect, and are caused by, social and economic inequalities in society.”
If we truly want to tackle health inequalities, advises the Marmot commission, we need to address “inequalities in the conditions of daily life and the fundamental drivers that give rise to them: inequities in power, money, and resources.”
I wonder if such inequalities also impact our ability to delay eating a marshmallow…
). 
