I made the observation to my husband the other day that when our eldest was around 1-1/2 years old, people would frequently comment that it was “such a fun age.” Funny, now that he’s 3-1/2, people aren’t saying that anymore.

This age, if I had to characterize it, I would say is one of extremes. It brings amazing demonstrations of imagination, insight and sophistication coupled with bouts of exasperating lack of self-control and flat-out cruelty. An example of the latter: his younger brother will be happily toddling along en route to something that has caught his attention and his brother, unprovoked, will give him a full-on, two-armed shove that will send him hurdling floorward. The cry this elicits when the younger connects with said floor is one of heart-wrenching woe and incomprehension. “But why?” it asks. It seems the more blithely oblivious the younger is, the more the older feels compelled to wreck his happy sanctuary. Because he can.

It’s hard as a parent not to watch and wonder what demon has come to possess my little angel, who just yesterday was himself the giddy, grinning toddler. But as quickly as I think it, he’s another self, spinning some outlandish tale that includes scraps of vocabulary that he has collected like shells on the beach but can’t quite marshal into proper usage (i.e. “olfactory instrument,” which he heard in the movie “Babe” and uses as an adjective to describe “truck”).

What’s going on in his rapidly developing brain may not be as warm and fuzzy to witness as watching him learn to walk was, but it’s every bit as important. What he’s learning is self-control and experts have become increasingly aware that mastering this skill is of fundamental importance to children’s success in life. I read a fascinating article about this in May in the New Yorker, which interviewed a researcher famous for his “marshmallow test.” Over decades, he was able to show that children who were able to delay eating a marshmallow based on the promise of a greater reward if they waited were consistantly found to be more successful in life. This is an excerpt:

Psychologists have focused on raw intelligence as the most important variable when it comes to predicting success in life. (Stanford professor Walter) Mischel argues that intelligence is largely at the mercy of self-control: even the smartest kids still need to do their homework. “What we’re really measuring with the marshmallows isn’t will power or self-control,” Mischel says. “It’s much more important than that. This task forces kids to find a way to make the situation work for them. They want the second marshmallow, but how can they get it? We can’t control the world, but we can control how we think about it.”

Similarly, preschools are increasingly focusing on “executive function” — children’s ability to order their thoughts, process information and avoid distractions. A New York Times article in September looked at a couple schools that are at the forefront in forming curriculum to help develop this fundamental ability.

But it’s so hard. Even we adults struggle mightly with delayed gratification. While writing this post, I ate a chocolate chip cookie I intended to save for my after-lunch sweet craving. So I can forgive my 3-year-old for falling prey to an impulse or two. And tempting as it is, I won’t be trying any home marshmallow test. As the song goes, “Que sera, sera.”