1) Yes, presumably; your brain is a vast store of (evolved)(wetware)(non-serial)(ad-hoc)(etc.)algorithms that has so far been difficult for neuroscientists to document.

2) Just plain empirical? There's nothing stopping you from learning your own source code, in principle, it's just that we don't AFAIK have scanners that can view "many" nearby neurons, in real time, individually (as opposed an fMRI).

3) Well that's much more difficult. Not sure why Mark_Friedenbach's comment was downvoted though, except maybe snarkiness; heuristics and biases is a small step towards understanding some of the algorithms you are (and correcting for their systematic errors in a principled way).