__________ is the most common reason young infants cry

An organized system of assumptions and principles that purports to explain a specified set of phenomena and their interrelationships is called a(n) __________

a. hypothesis. b. operational definition. c. research design. d. theory.

The fundamental biological process underlying dark adaptation and light adaptation

is (a) opening and closing of the pupil (b) flattening and bulging of the lens (c) the breakdown and restoration of light-sensitive chemicals on the retina (d) neural processes in the brain