I did read "Blink" and found that while he provided lots of anecdotes to support his premise, there was no mechanism, no measurement, and no way to verify it. In fact, he provided a number of other anecdotes that showed just the opposite.
What he did in that book, I think, was to state a premise that we'd like to believe, that our gut instincts are right, and tell stories to reinforce that, but never go so far as to make a claim that could be verified. I'm not alone in this view.
Based on what I've read so far, "Outliers" seems like more of the same.
You might be interested in Antonio Damasio's book "Descarte's Error" in which Damasio scientifically presents evidence that the majority of our reasoning is in fact mediated by emotion and "gut feeling" linked to situational stimulus. Damage to the pre-frontal cortex of the brain (see: Phineas Gage) impairs this "secondary" emotional system and causes quantifiable decision-making deficits. Gladwell is referring to just this system in Blink, and although he does occaisionally lapse into pop-sci there is a significant body of work that supports his main conclusions.
As another interesting aside, this is why teenagers have such a poor time making good long-term decisions. The pre-frontal cortex is one the last places in the brain to fully mylleinate (develop), and so their emotion-based reasoning system does not fully come on line until they are 18-22. As the insurance commercial goes: Why do teenagers driver like they're missing a part of their brain? Because they are.