Humans have ____pairs of chromosones.

An issue with longitudinal research is 

Operant conditioning focuses on ____ or ____ behavior.

____ refers to the minimum amount of stimulus energy required to be detected 50% of the time.

____ are sequences of DNA.

____ refers to the way sensory information is organized and interpreted.

Associative learning refers to connections between ____ and ____.

____ reinforcement occurs every time there is a desired response.

The ____ is the opening in the eye that allows light to pass through. 

A menstrual cycle is a ____