Of the main topics presented in a course on organizational psychology (communication, decision making, emotions/personality, and diversity), which ones are the most important in the work place?
Organizational psychology, when associated with the work place, is known as Industrial Organizational Psychology (or I/O Psychology). I/O Psychology is broken into two specific branches (per the name): industrial and organizational.
The industrial branch examines the matching of personnel to specific job placement. For example, an extrovert would perform well in jobs which allow them to work with the public. Introverts, on the other hand, would not be well suited to work in the same positions.
The organizational branch examines the functioning of personnel within a company. For example, the organizational branch would examine the effects defending criminals upon the lawyer's mental and physical well-being. This branch also examines the different management styles, expectations of the position, and the structure of the company on the individual.
In this sense, communication, decision-making, emotions/personality, and diversity all play a part in I/O psychology. Communication, emotions/personality, and diversity are all important on the industrial side, while decision making and communication are important on the organizational side. One does not necessarily have more importance over another given the whole of the environment is studied.