This sense is important to the development of other brain functions because the earlier babies can explore the world, the quicker they will learn. Smell is a primitive sense, and it is extremely important to other mammals. In humans, it is mature at birth. Fetuses can smell in the womb during the last trimester. This promotes bonding of the infant to the mother after birth.
Infants also recognize the smell of their mother's breast.
Fetuses are also capable of tasting in the womb. Taste preference is malleable, but all babies prefer sugar since it satisfies their taste abilities at birth. Eating sweet foods releases endogenous opiates in the brain that induce a sense of pleasure and well-being. Sour-preferring cells in the tongue are the last to develop. Vision, on the other hand, is poor in humans at birth.