In younger children these neural connections are still budding (these brain circuits don’t finally finish maturing until the mid-twenties), which explains kids’ zany, sometimes maddening antics, where their whims drive their actions. But between ages five and eight, children’s brains have a growth spurt in their impulse control circuits. The ability to think about their impulses and just say “no” to them makes third graders less wild than those boisterous first graders down the hall.
— Focus: The Hidden Driver of Excellence (Daniel Goleman), Loc. 2561–4