A person's ability to resist temptation, tested at age 4 when five hundred children were told they could get two marshmallows if they could wait fifteen minutes before getting the second one, has once again proven to have lifelong predictive power, this time forty years later with 59 of the original subjects, now in their mid-40s.
The middle aged adults were given a new, age appropriate test of impulse control involving refraining from pushing a button in a laboratory test in response to images displayed on a computer screen, and those who had willpower at age 4 also had it in their 40s, while those who did not have it then didn't have it later. Functional MRI scans of half of the subjects showed that resistance to temptation was related to activity in the brain's frontal lobe.
The study is one of the most notable elements of a larger effort to identify stable cognitive traits that are largely independent of IQ that impact a person's life chances in the modern world.
A cluster of traits, with one end of the scale associated with the Big Five personality trait of conscientiousness, and traits such as willpower, self-discipline, grit, initiative, personal organization, and what Steven Hsu has called the "W" factor for work ethic, have found themselves juxtaposed against the mental health condition ADHD, and traits like novelty seeking, impulsivity, and tendency to procrastinate. The way that psychologists define these traits isn't identical, but there seems to be heavy overlap between them. See, for example, prior posts here and here, here, here, here, and here.
The dopamine systems and components of the brain involved in one seem to overlap heavily with those involved in another.
Increasingly, it is becoming clear that these traits are congential or fixed in early childhood, possibly with a strong hereditary component, and are stable throughout life, although the way that they manifest at different points in a person's life varies. Whatever its etiology, the trait seems to be fixed, at least absent concerted and highly exceptional intervention, before kids even start first grade. Early childhood and elementary educators may hope to intervene and change this, but certainly for high school teachers and adults, people pretty much are what they are going to be and it seems likely that it isn't much more possible to change this trait appreciably at that point than it is to change someone's IQ at a comparable age. Indeed, impulsivity seems to be pretty stable at ages 3-4, while children may be twice as old before their tested IQs are really stable.