In biology, a pigmented area that is sensitive to light.

A second series of lenses that magnifies the primary image, producing the image that is projected to the retina of…

A reflex jerking of the head in infancy in response to light.

Protrusion of the navel.

The instinctive motion of the tongue by which infants push food out of their mouths.

Reward that is received from an external source as the result of a person’s behavior or action.

Extrinsic reward.

The environment outside of the person.

In type theory a person whose personality is oriented outward, requiring continual stimulation from the social environment, introvert.

A pregnancy that occurs outside the uterus.