Hum, I'm not certain how experts tell the difference. Robin Williams I think is an example of histrionic behavior....it's like over the top and flamboyant lots of physical gesticulation. I sort of think about NPD as being conniving without all of the exaggerations.
There is cross over you know. People don't fit neatly into a category sometimes.
Also the "experts" get together and rewrite this stuff from time to time and even they can't always agree on how to organize these things or if they should even exist.
I would say there is a difference though. My mother seems more Narcissistic without a lot of Histrionic traits. There would be some Narcissistic people though who would have histrionic type traits possibly. There could also be Histrionic people who had Narcissistic traits. That's why people get PhD's in this stuff.
You know the Narcissists think they are better than other people.
Histrionics want to show you that..... they have something to show you. Hey look!! Hey I'm crying!!! Now I'm laughing!!! Now I'm jumping. Wait no go away...no I was just kidding...no really go away....but I'm going to stand right in front of you while you are walking away....because I'm walking away faster than you...what you are going home?....okay, not before I cry first.
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ICD-10
F60.4 Histrionic Personality Disorder
Personality disorder characterized by at least 3 of the following:
(a) self-dramatization, theatricality, exaggerated expression of emotions;
(b) suggestibility, easily influenced by others or by circumstances;
(c) shallow and labile affectivity;
(d) continual seeking for excitement, appreciation by others, and activities in which the patient is the centre of attention;
(e) inappropriate seductiveness in appearance or behaviour;
(f) over-concern with physical attractiveness.
Associated features may include egocentricity, self-indulgence, continuous longing for appreciation, feelings that are easily hurt, and persistent manipulative behaviour to achieve own needs.
Includes:
* hysterical and psychoinfantile personality (disorder)
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Miss Piggy might be a histrionic. She might be antisocial also. Maybe a Narcissist
Kermit might be normal.
Animal would definitely be antisocial.
So Narcissism defined by Hotchkiss:
1) Bad boundaries
2) Exploitation
3) Entitlement
4) Envy
5) Arrogance
6) Magical thinking
7) Shamelessness