There's some interesting research around. More than 50% of all women in the UK admit they fake orgasms on a routine basis. Yet only 10% of men think they get the occasional fake orgasm from their partner.
This clearly indicates most men cannot spot fake orgasms.
This is a brain thing, connected to similar research about recognizing smiles and generating lies.
-psychologists know that most people are bad at lying; there is only about 10% of the population that can formulate a good lie, without giving away subconscious signals (such as facial micro-expressions).
-psychologists also know that most people are not capable of recognizing fake from real smiles; the same area in the brain is at work; the same 10% of the population can spot *all* fake smiles from a list, consistently.
You can test your skills here: BBC - Science & Nature - Human Body and Mind - Spot The Fake Smile
The test takes about 10 minutes, is science-based and teaches you a lot about yourself.
Let us know your score. And be honest.
Note: the group making up this 10% of people capable of spotting fake human expressions and emotions flawlessly, contains a disproportionally large number of psychopaths. Apparently psychopaths are very good at spotting other people's emotions and at defining them precisely (which explains why they're such successful manipulators), but they are incapable of having such emotions themselves.