Babys/Toddlers spend 50% of their sleep in REM sleep compared to adults 20%. This is when their brain grows. In this case, your child is as “smart” as the amount of sleep they get. They learn when their brain is the most active. At 3 months Legend was sitting up and posing, I didn’t know why and how.
This explains why children have a mass growth spurt before the age of 5. Legend is Autistic so he slept initially 15-17hrs & now 12-15hrs consistently. His brain requires more rounds of REM; Need I say, All Kids Need Sleep, putting them to bed is very essential 🙏🏾
To add, We all transition from REM to NonREM sleep (which is where our bodies heal). Children bodies does not require as much tissue growth needed, body repairs, building of immune system, etc. As to why the older you get, the lighter you’ll sleep.