OK, here's a few ways of expressing observable anger off the top of me head:

sarcasm

defensive whining

condescension

belligerence

indignation

hostility

stubbornness or intransigence

sneering

Any of the above observable behaviors can be explained as observable manifestations of an angry person.

The study of personality, behavior, and especially of addiction, is nearly all hypothetical--with virtually NO theoretical base right not. Brain research is very much in it's infancy--scientists are still mapping the brain!

Now, it is quite fascinating that MRI has been used to further identify where in the brain things happen under a wide variety of circumstances, it is all still quite baffling and unknowable.

For instance, one part of the brain often associated with emotional expression is the amygdala. However, studies into emotional behaviors of that particular part of the brain are also contradictory, because emotional responses routinely show up also in the hippocampus, pallidum, and caudate nucleus regions of the brain.

While it may be fascinating that some studies done on bipolar disorder in children shows up in the amygdula (just as one example), that doesn't "prove" anything in a scientific sense. At least not yet. Why? Because the difference seems to be the in the stimuli used in the study, not in the anatomy of the brain itself.

So to make these sweeping statements like "anger is addictive" or "love is addictive" is akin to saying "rice pudding is addictive".