CM (F) 42
Sydney, Australia

Response: It really depends on his age.  What you are describing is typical behavior for a 21-34 year old man, or woman in her twenties who has never been married, in both cases without children.  Kids tend to be the great humbler. 

Bravado, arrogance, showboating, bragging, acting tough, speaking in absolutes, being a know-it-all, these are usually signs of insecurity. It is a defense mechanism, a way of keeping people from getting too close and cloaking fears by portraying the opposite of what the person is feeling.  This is one reason women in their twenties have trouble allowing men to treat them like a lady, opening doors, paying for dinner, etc...They do not want to be seen as dependent.  Once they become comfortable with who they are, usually by their mid-thirties if single or upon motherhood, this need to be seen in control disappears.

Men do this to appear bigger, smarter, richer or more powerful than they are.  Some call it posturing. Picture a rooster ruffling his feathers to look bigger and all poofed-out as he struts around.  This is a visual of what your co-worker is doing when he goes from sweet to smarmy. The secret is he does care what people think or he would not feel the need to act tough disproportionate to the threat.  It is appropriate if let's say five gang members corner him in a dark ally; but I'm guessing there are no gang members or dark allies in your office.

If he's in his late thirties or forties and still acting like this, he probably is dealing with uncertainty in his personal or professional life and over-compensating in an effort to protect himself. The behavior will diminish with the level of perceived threat and eventually disappear.  Perceived being the key word.

Yet the office isn't the only place you will find this type of behavior. You see this in politics as well.  The euphemism or spin used to describe and dismiss it is "determined, steadfast, resolute". But there is a difference between being focused and goal oriented with the flexibility to change direction based upon new information and just plane stubborn and refusing to admit a mistake or reverse coarse.  Goal oriented and flexible is maturity.  Stubborn and inflexibility is immaturity.  The difference between an adult and a child is the ability to understand cause and effect and redirect your energy based upon situational dynamics with paramount concern for what is in the best interest of all, instead of what is best for your own ego.

Bravado, arrogance, the need to always be right, the inability to compromise or engage in diplomacy, confrontational attitudes this usually disappears with maturity, sooner in women than in men.  Of course, there are always exceptions to the rule.  I'm sure you can think of at least one high profile poofed-out rooster strutting around the world stage, crowing and acting like God. Your poofed-out rooster doesn't have nuclear weapons at his disposal and will likely grow up and out of his brusque and abruptness...ours on the other hand is poofed on steroids and fully loaded....and as he's well into middle age, it is doubtful he will ever grow up.  Not to mention our's pretends he's a cowboy but is afraid of horses. Your office got the better deal.  Want to trade?:)  -LDL