Dec 10 2015

Delayed Gratification and the Brain

Neuroscientists, both psychologists and neurobiologists, have been studying the phenomenon of delayed gratification. This is the ability to make choices that deny oneself an immediate or short-term benefit in order to garner a greater long term benefit. A recent study looks at the genetics associated with the ability to delay gratification.

Researchers use a study paradigm known as the marshmallow test to study impulsivity and the ability to delay gratification. The first such studies were conducted in the 1960s and 70s by Walter Mischel, then at Stanford University. Children in the study were offered a small treat, such as a marshmallow, immediately, or were told they could have two treats if they were willing to wait 15 minutes, during which time the researcher left the child alone with the marshmallow.

Follow up studies found that children who were able to hold off on eating the marshmallow had numerous better life outcomes – better academic performance, more successful marriages, better careers, and lower BMI.

Not surprisingly, children with ADHD perform worse on the marshmallow test.

A study published in 2013, however, showed how difficult it can be to interpret behavior in contrived laboratory settings. The researchers added a trust element to the test, priming children to either trust or not trust what the researchers promise. Those who were primed to not trust the researchers were more likely to eat the marshmallow – they did not trust that the later reward was coming.

The current set of experiments use money and are studying early and late teenagers:

Anokhin’s team studied 310 adolescent identical or fraternal twin pairs and asked them questions about money. At 12 years of age, and again at age 14, they were given the choice of receiving $7 immediately or $10 in the mail two weeks later. At age 12, 35 percent decided to take $7 right away instead of more money later. That number fell to 27.5 percent when the same kids were presented the scenario at age 14.

They also studied identical and fraternal twin pairs at 16, 18, and 20 years old. They found a general trend of greater delayed gratification with age. This fits with our understanding of the maturing teen-aged brain. They did not control for trust or other variables, and so they can only conclude this “might” have to do with self-control and impulsivity.

So far none of this is terribly new. Because they were studying identical and non-identical twins, however, they were able to also mathematically model correlates with specific genes for brain receptors. The genes that correlated best were for kappa opioid receptors, and to a lesser extent serotonin. These receptors have been previously linked to things like depression and addiction. Now it seems they are also involved in decision-making and self-control.

This one study is not capable of disentangling the likely complex relationship among these various phenomena. Perhaps being a little depressed saps someone of their self-control. It seems likely that decreased self-control or delayed gratification is a risk factor for addiction. It’s also possible that these receptors have different functions in different brain regions and there may be no direct causal link. This is just one piece of a large and complex puzzle.

It’s also important to point out that such studies are looking for general statistical trends pointing the way toward some psychological phenomenon. That does not mean, however, that you can use that knowledge to understand the behavior of an individual in a specific situation. Human behavior is complex, and people do quirky things for quirky reasons.

Psychologists also talk about the “fundamental attribution error,” which is a tendency to assume internal causes for other people’s behavior (while assuming external causes for our own). Ironically, many psychological studies are premised on the assumption of internal causes for behavior – there is nothing more internal than looking for genes that correlate with a specific behavior.

Here is one example. In the current studies, in the older children, the researchers offered variable amounts of money now, like $85, vs a larger amount, $100, to be received in the mail six months later. I can think of lots of reasons why someone would take the $85 that have nothing to do with self control or the ability to delay gratification. Someone may have a genuine need for the smaller sum now.

Some people may also be motivated by closure. I may conclude that $15 is too small a difference to worry about, and I don’t want the loose end of waiting for the larger amount in the mail in six months. Unchecked mental boxes cause variable amounts of anxiety, and it may just not be worth it. There is also, of course, the issue of trust. People are also moody – someone having a bad day or who is mentally exhausted from some prior effort may just want to take the shortest and easiest path.

In other words, there are a host of external and complex internal reasons why a particular person might make a specific decision. That is why researchers need to look for statistical trends, but even then such trends are subject to systematic influences that are not accounted for.

All of this does not mean that psychological research is impossible, just difficult and complex. It means we have to interpret studies with care, and only rely upon robust research that has approached questions from many different angles.

It also means – resist the urge to interpret the specific behavior of an individual with the latest bit of psychological wisdom.


There is a great deal of research suggesting that the ability to make strategic decisions, to defer short term benefits or gratification for longer term goals, is a specific identifiable brain function, which psychologists call executive function. People vary according to their executive function just like people vary with respect to any measurable trait.

Executive function has also been robustly tied to a host of life outcomes, which all plausibly flow from this cognitive ability. There is a great deal of research suggesting that genetics plays a large role, and that people have an inherent executive function ability, just like people have varying amounts of talent for music, math, or language.

Genes are not destiny, however. Research also suggests that executive function can be improved by exercising it. This also fits the general trend – anyone can become good at music, for example, it just may take a lot longer for some than for others.

At the low end of the executive function Bell curve are those who have real difficulty. They are often labeled ADHD. While cognitive and behavior therapy is helpful, they may also benefit from medication to help the executive function part of the brain function more robustly, especially during high demand times like school.

ADHD is no different than dyslexia or delayed language and it should not be stigmatized. It should also not be denied – no, it wasn’t invented by Big Pharma as some claim.

Studies like the current one add one more notch to our understanding of this important and complex neurological function.s

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