When my son was six months old, he couldn't crawl. I mentioned it casually on the phone with my aunt. She's a retired pediatrician. That weekend, she took the high-speed rail from Jiangsu to my place.
She didn't sit around explaining theories. She got on the floor herself, held my son's limbs, guided him through the motions. By evening, he was crawling β genuinely coordinated, moving forward.
She stood up and said: "There's nothing wrong with the kid. Nobody's seriously taught him how."
It stung a little, but she was right. I thought I was waiting for him to develop naturally, but there was something I could have been doing.
Crawling trains the corpus callosum β the bridge between the brain hemispheres. It's not training the legs. It's training the brain.