A mother is breastfeeding her infant son. A ‘let-down reflex’ releases milk from glands in the breast into the ducts from which the infant sucks. At first, the let-down reflex is elicited only when her infant's lips touch the nipple and the baby starts sucking. But the infant often cries just before he nurses. Soon, the mother exhibits the let-down reflex every time her baby cries, even though sometimes he doesn't want to be fed at all. In this example ___