But if we are talking any real sort of confidence, the main way it develops is through success, which requires manifesting attractive behaviors in the first place.
Exactly. But in the version of the experiment I proposed, both groups are composed of (initially) inexperienced geeks, as opposed to pjeby's protocol, which involved an untrained newbie and a PUA trainer (who, despite having trained on, IMHO, potentially invalid methods, has likely acquired a great deal of real confidence via experience).
Which is why, now that I've had some time to think about it, I now predict that if this experiment were performed, both trainee groups would "go barreling into interactions and just as easily alienate people as engage them". For it to mean much, you would have to iterate the experiment over a period of weeks or months and see which group improves faster. I remain agnostic on what the outcome of that would be.
I was thinking along our lines, where both groups involve newbies. I predict that the confidence will collapse in whichever groups lack some actual practical knowledge that can achieve success to keep the confidence boosted.
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: