Azi, Dan -- I think you're simplifying too much. The Israeli method does not rely so much on detecting involuntary physical behaviors, as these are very weak indicators; the more important indicators are people's stories as to where, why and how they're traveling, and this requires having a conversation with every passenger. Of course, it's impractical to give each passenger a 5-minute interview, and this is where profiling comes in, where passengers who fit a low-risk profile get a very short interview (perhaps 1 or 2 sentences), while others are interviewed more extensively.
Israeli screeners do work by a book, and while the criteria for determining risk are not published (for security and other reasons), it's not hard to figure out what some of these are. Some of the criteria for profiling would be illegal in the USA, other parts of the world, and even in Israel, which regularly creates funny exchanges (e.g. when screeners try to determine your ethnic or religious background without asking about it directly). Other criteria for profiling, however, are perfectly legal (e.g. asking who owns the laptop you're carrying).
As for Dan's claim that everyone is trained, I can say from my own experience as a semi-frequent traveler to Israel who (probably) fits a medium-risk profile that it's very easy to spot newly-minted screeners and their awkward behavior when they try to apply their training to slightly complex situations. One thing they are trained for, though, is to very quickly call an experienced supervisor when they feel they're not sure how to handle a particular situation.