What do we know to be true about infant physical development? The infant's brain develops from 100 billion neurons to 500 billion in a very short period of time.
The infant's brain starts with about 100 billion neurons and over time the connections between these neurons dramatically increase.
The only reflex the infant is born with is the rooting reflex, which is essential for feeding.
Motor development (e. g., sitting up, crawling) unfolds exclusively as part of a genetic plan.
The infant is able to reach for objects early because it is such a simple motor skill.