In grad school, my adviser insisted that they could be used interchangeably in the context of our field (in the humanities). I know that in psychology, affect is the correct spelling for the emotional expression of a patient, and I always use effect when it is a verb (to effect change, etc.). But what about the regular old "effect of this issue on the whatever" or "has the effect of polarizing" or "how this may effect popular views of ... etc." Right now all of these look wrong to me using EITHER spelling but I have to say this word a lot in what I am writing right now, and it is driving me a little crazy. Today I am in an affect state of mind but usually I am in an effect state of mind. What about you guise?