Psychology of the Dominant. Great subject, I wrote the psychology of a chicken and got it published, so I may have a stab at this (there has to be some correlation).
The OK Dom
Your average Bloke in day to day life: For some, as others have said, it's about the need to be in control of others because of a lack of control of some aspect of their life. I wouldn't necessarily call this person a Dominant person, but someone who "enacts" Dominant behavioural traits (as they see it) as a panacea to some aspect of life which they're unhappy with. D/s is used as a "stress" release and a way to maintain their own self worth. Through D/s they achieve some balance in their life. They'll be pretty normal, and a relationship will mostly work well, more than anything, they're human beings.
The Unbalanced
Affective or Personality Disorders: At the extreme end, you sometimes find disorders such as Borderline Personality Disorder and Bi-Polar, who take the role of Dominant due to a lack of control of their own emotions. Characteristic of these disorders will be mood swings. Loving at some points, angry and demanding at others, and there will be times when nothing you do pleases them. These people have over-riding self worth problems, and no matter how much you devote yourself to them, you won't alter their self perception (it's about their thoughts, not your actions). NPDs or people with Narcissistic Personality Disorder. These one's don't consider the effect of their behaviour on others, all of their actions are focussed purely on their own needs, and often a-moral views on life. Big warning and danger sign with these people. They are the ones most likely to rage, and pay no attention to limits. Your wants aren't a factor in their life, neither are your emotions. Humiliation will be a big player for both of these groups of people. They need you to seem less worthy than they are. True Sadists are likely to have NPD traits. The submissive which best suits them is also someone with negative self worth (who wants someone to tell them they are worthless and beat them because they believe they are worthless). This type of a relationship is a co-dependent one. An alternative "partner" for them, is someone who has something called a maladaptive self sacrifice schema, who see's their beloved Master's underlying unhappiness, and wants to devote themself to making them happy. They won't.
Wannabe's
Your HNG/Troll Dominant: They see BDSM as an easy way to get sex. You don't find them under bridges curiously enough. Most likely they will have had little sexual experience, few long term relationships, and not be good at relating to other people's emotions, possibly even be intimidated by women, and have the false perception that a submissive is easier to get into bed because they only say "yes Master". They see a submissive as a less complex person with fewer needs. They want their submissive to be Pamela Anderson. Airhead submissives, or those desperate for a shag apply here.
The Self Centered Male: Fetch my pizza slut. Let me watch the football while you blow me. Need I really say more. In some ways, they want the submissive to be a cross between their Mom and Pamela Anderson. Doormat submissive... the perfect match.
Balanced Doms
A "Modern" Master: They are a Dominant personality because they are in control of themselves, which allows them the stability to guide, teach, and care for others. They'll normally come across as pretty relaxed in day to day life, because they are pretty happy with themselves. Their role will extend further than the bedroom, and be focussed on protection, and care. Pain play, if used, will be linked to stimulation and attaining sub-space - not so much a Sadist as a Sensate. Less likely to use humiliation in scenes as their focus is building self esteem. They also want to continue to learn. They will want a submissive who is intelligent and vibrant.
The Traditional Master: Believes that traditional roles of the Male of the household wearing the trousers is the correct one. Where a submissive shares this view, they will find a mutually fulfilling relationship. His duty, to decision make, provide, direct, and hers is to nurture and to serve. BDSM scening is an extension of this relationship. Not one for the emancipated submissive, but fulfilling for those who want this.
A Kinky Dom: Pretty well balanced with a love of the trappings of BDSM for play and sexual stimulation. For any submissive who wants to scene in the bedroom, but a vanilla life outside.
Got to be a few dozen more, but this may get you started.
Joe
