I attended a Siebel Institute seminar on off flavors like 15 years ago and it was an eye opening experience. What they do is take a very bland beer like Miller and present you with 6 samples of it, if I remember right, that are each spiked with one of the major off flavors and one sample that is unadulterated.
It was one of those moments when I realized that a lot of the beer I'd been drinking were not being produced the way they should be.
It also teaches you that everyone's palate is different and most people have one or two off flavors that they have trouble perceiving and one or two that they are hyper sensitive to. Mine were the solvent like flavors which I really can't detect at all and Diacetyl (buttery) and Aldehyde (green apple) which I swear I can sometimes smell from the glass of the person standing next to me.
I've got to tell you that being able to recognize off flavors can be a bit of a curse because of how many beers have some type of flaw. It also makes you really appreciate a well crafted beer where there is balance between the various flavors and no off flavors.