While Skinner (1953) had suggested we all might display multiple personalities, Kohlenberg (1973) first proposed a learning theory account for multiple personality (Phelps, 2000). It can be argued and observed that each of us has differing amounts of variance in our personality repertoires to the point that a common question may arise: "How many personalities do we actually have?" The question isn't how many personalities do we have, but how many behavioral repertoires are each of us capable of performing or exhibiting?
Viewing personality this way, it is obvious that we all execute multiple personalities, with differing grades of behavioral excesses and deficits, beyond what is "normal." These behavioral variations are due to our unique histories of differential stimulus control, reinforcement and punishment contingencies and observational learning experiences (Phelps, 2000). That is to say, we may behave very differently in a lecture hall than when in a church, synagogue or mosque. Any individual no doubt behaves very differently when with one's mother than when with friends at a convention. Despite the variability, an observer would still see "It's still Joe" or that there was enough stability or generalization in Joe's personalities across all contexts for Joe to be recognized as the same person.