Public speaking vs. interpersonal speaking

Okay keyboard psychologists, help me with this one.

A lot of people are petrified when it comes to public speaking, but have no problems talking interpersonally.

I’m just the opposite. I have few problems public speaking, but speaking interpersonally I come across as mildly retarded.

Is there a plausible psychological reason for that?

I’ve considered a few things: With public speaking, you’re speaking AT people, with personal speaking, you’re speaking TO people. Or, with public speaking, you’re not playing the role of yourself, you’re playing the role of presenter; with personal speaking, you have to play the role of yourself. Stuff like that.

I don’t know.

Diagnose me with something.

They have names for every foible nowadays.

Public speaking just involves a different set of skills from private conversation, and it’s certainly possible to be naturally good at, or have developed skill in, one more than the other.

Public speaking…

…is something you can prepare for ahead of time. You can plan, in as much detail as necessary, what you’re going to say and how you’re going to say it.

…leaves the speaker in control. You don’t have to respond to what the other person says, or worry about the protocol of relinquishing and regaining the speaking role in the conversation.

…usually involves speaking on subject matter that you know something about (or at least have the ability to study up on). Interpersonal communication is often more nebulous, involving feelings, personal experiences, small talk.