Raymond Cattell expanded on Spearman's idea of a two-factor theory of intelligence after performing his own tests and factor analysis.

This is known as Spearman's two-factor theory.

They contrasted the modern hierarchical theory of g with Spearman's original two-factor theory which was readily falsifiable (and indeed was falsified).

The misattribution of arousal study tested the two-factor theory of emotion.

This theory has helped support Schachter & Singer's concept of the two-factor theory.

Though the authors expected the two-factor theory to be the most effective, it actually proved to be deleterious in outcome.

The authors note two-factor theory involves stark disapproval of the clients' "irrational behavior" (p. 350); this notably negative outlook could explain the results.

There are many theories of motivation which include, Abraham Maslow's hierarchy of needs, Herzberg's two-factor theory.

A two-factor theory of love was developed by Barnes and Sternberg.

Both of these models drew upon Herzberg's two-factor theory of motivation.