Critical thinking
Article: Cronbach (1957)
The two disciplines of scientific psychology

The separation of the disciplines

The experimental method, where the scientists changes conditions in order to observe their consequences, is much the more coherent of our two disciplines.

Correlational psychology was slower to mature.
It qualifies equally as a discipline, because it asks a distinctive type of question and has technical methods of examining whether the question has been properly put and the data properly interpreted.

The well-known virtue of the experimental method is that it brings situational variables under tight control. It thus permits rigorous tests of hypotheses and confident statements about causation.

The correlational method can study what man has not learned to control or can never hope to control.

Characterization of the disciplines

In the beginning, experimental psychology was a substitute for purely naturalistic observation of man-in-habitat.

The experiment came to be concerned with between-treatment variance.
And, today the majority of experimenters derive their hypotheses explicitly from theoretical premises and try to nail their results into a theoretical structure.
The goal in the experimental tradition is to get differential variables out of sight.

The correlational psychologists loves those variables the experimenter left home to forget.

Factor analysis is rapidly being perfected into a rigorous method of clarifying multivariate relationships.
The correlational psychologists is a mere observer of a play where Nature pulls a thousand strings: but his multivariate methods make him equally and expert, an expert in figuring out where to look for the hidden strings.

The shape of a united discipline

It is not enough for each discipline to borrow from the other.
Correlational psychologists studies only variance among organisms; experimental psychology studies only variance among treatments.
A united discipline will study both of these, but it will also be concerned with the otherwise neglected interactions between organismic and treatment variables.
Our job is to invent constructions and to from a network of laws which permits prediction.

From observations we must infer a psychological description of the situation and of the present state of the organism.
Our laws should permit us to predict, from this description, the behaviour of organism-in-situation.

Methodologies for a joint discipline have already been proposed.