[grabbalacious]

One of the issues is that humans don't reason what the current situation is prior to emotional response and action. Rather their emotions about the situation are inputs into the reasoning process.

e.g. The fear elicited upon perceiving a particular person causes the conclusion that he is dangerous, not vice versa.

The multifarious causes of emotions are notoriously difficult to trace, and can indeed be somewhat noisy. Thus most people are effectively just rationalising when asked why they behaved as they did.