I recently finished reading Blink: The power of thinking without thinking, a wonderfully written book by Malcolm Gladwell which goes into the details of intuition, first impressions, subconscious judgements, involuntary prejudices; the snap-judgements we make within seconds of seeing something.

He illustrates his points with a myriad of fascinating examples and experiments which make this book a captivating read.

More to whet your appetite for this, and his other books, here