Dr Emmerson was the first to detail Ego State techniques for Addiction, Depression, Couples Work, and Obsessive Compulsive Disorder. He developed the ‘Expression, Removal, Relief’ method of trauma resolution, and was the first to present ego states as either surface or underlying, and as being in one of four conditions, Normal, Vaded, Conflicted, or Retro. He has presented an integrated theory of personality and therapy based on his concept of ego states, providing therapists with a directional flowchart of techniques depending on the presenting problem. He has devised diagnostic criteria to inform ego state therapists about the preferred course of therapy.

He currently conducts Research and Statistics workshops for ACSPRI in Australia and NZSSN in New Zealand, and trains therapists in Resource Therapy (Ego State Therapy) in Australia and overseas.

He has held the positions of Professor at Kansas State University and Honorary Fellow at Victoria University, Melbourne.

He has served as Victorian State President of the Australian Society of Clinical Hypnotherapists and Vice President of Ego State Therapy International (ESTI).

He has authored five books, Ego State Therapy, 2003, 2007, 2010; Advanced Skill and Techniques in therapeutic Counselling, 2006; Healthy Parts Happy Self, 2012; Resource Therapy - Primer, 2014; Resource Therapy, 2014, Resource Therapy Trainer's Manual, 2014 and has published experimental studies and theoretical papers in numerous refereed journals, has acted as the associate editor of the Australian Journal of Clinical and Experimental Hypnosis, and is a registered psychological examiner and psychologist. He has conducted over 200 workshops in Australia, Middle East, South Africa, New Zealand, the UK, Europe, the US and Indonesia.