Conversation so far:
What is multivariate research?
Raymond Cattell pioneered the use of multivariate experimental psychology (the analysis of several variables simultaneously).
What else can you tell me about multivariate research?
The multivariate approach allowed psychologists to study the whole and their unique combination of traits within a natural environmental context.
What approach was being used before the multivariate?
Univariate and bivariate research approaches were more commonly used before the multivariate approach.
How did the multivariate research approach help research?
Multivariate experimental research designs and multivariate statistical analyses allowed for the study of real-life situations that could not be manipulated in an artificial laboratory environment.
Rather than pursue a univariate research approach to psychology, studying the effect that a single variable might have on another what?
Rather than pursue a univariate research approach to psychology, studying the effect that a single variable might have on another variable, Cattell pioneered the use of multivariate experimental psychology.
How is multivariate research different from other methods?
Instead of focusing on just one variant or two, the new approach allowed its user to focus on multiple variants simultaneously.
Has the multivariate research been applied?
Raymond Cattell applied multivariate research methods across several intrapersonal psychological domains: the trait constructs of personality, motivational or dynamic traits, mood states, as well as the diverse array of cognitive abilities.

Question: What types of domains?
Self-contained rewrite: What types of domains has the multivariate approach been applied to?