If I were the parent of a child who ate the marshmellow too quickly, I would do nothing different, as the whole thing is meaningless and doesn't change anything. It's more like, "Oh, OK, my son is 4% less likely to be in the top 20% of the income distribution (according to this barely coherent theory)." Why do we spend so much money, time, and effort discussing and researching this?
Teaching a child to do basic budgeting with pocket money is likely to have a vastly higher impact than slight delayed gratification with candy.
Further, the result in a recent replication [1] was a correlation of .28 between the time to ring the bell (to get the marshmallow) and academic achievement. That's not exactly the trivial "4% less likely" effect in your caricature.
(You may also wish to double check your spelling of "marshmallow.")
[1]: https://www.jasoncollins.blog/posts/the-marshmallow-test-hel...
You clearly don't know how to interpret correlation. A correlation of .28 is virtually uninformative. https://www.academia.edu/39797871/Fooled_by_Correlation_Comm...
I.e. it's a covert test if parents are rich.
The only thing that children of rich parents share is to have rich parents. One of the parents being over the mean in the "beautiful" trait, is also very common.
Do you have evidence to exclude other possible interpretations, such as the possibility that children resisting the temptation of a marshmallow and their parents being rich are actually the effects of some other underlying single cause?
Stop and think.
If you are rich that marshmallow is probably very bland or you've eaten very well today. So maybe two makes more sense.
If you aren't, that marshmallow is super tasty and you probably didn't eat well today. Plus do you believe that grownup when your mom was lying. Someone might come and eat it.
Then some time passes. Rich kids grow up and are more successful. Delayed gratification is key to success!
https://behavioralscientist.org/try-to-resist-misinterpretin...