Final answer:
An infant turning its head towards a sensory stimulus is exhibiting an orienting response, which is one of several reflexive behaviors that aid survival.
Step-by-step explanation:
When an infant turns its head toward a sight or sound, the infant is engaging in an orienting response. This is a reflex action where an infant automatically turns their head and eyes in the direction of a sensory stimulus. Reflexes like this are important as they help the infant survive by responding to changes in the environment. For example, the rooting reflex is another instinctive action where a baby will turn their head toward something that strokes their cheek, in an attempt to find food, which usually would be the mother's nipple.
Newborn reflexes such as crying, sucking, and the Moro reflex are all part of an infant's rapid motor responses to ensure survival. These actions are innate and do not require the involvement of the brain but instead travel through an arc that includes the spinal cord. Newborns are biologically programmed with these reflexes to respond to the world around them, even though their sensory systems are not yet fully matured.