Which researcher argued that as much as 80 percent of intelligence is a result of heredity?

The ____ method uses independent and dependent variables to reveal cause-and-effect relationship.

a) correlational b) descriptive c) experimental d) observational

In Skinner's experiments, a rat pressed a lever and received food. This process strengthened lever pressing. The food is a(n) __________. The lever pressing is a(n)__________. The process is called ______________

Fill in the blank(s) with correct word