According to the lecture and textbook reading, psychology is a broad, diverse field of professionals with varied interests. What, if anything, unites the field of psychology per your textbook author?

As per textbook author, the thing that unites the field of psychology is the responsibility and urge to understand, use, or apply the scientific method.

Explanation:

Psychology:

It is defined as the branch of science that deals with the study of behavior and mind of individuals.

In Psychology, we do researches that are beneficial in many fields of life like human development, personal growth, sports, etc.