If a story is spread by being told from person to person, the final version will be very different from the original one. That makes it difficult to define or delimit memes. There are several selection criteria which determine in how far a particular meme will be successful. Objective criteria determine whether the knowledge conveyed by a meme can reliably predict events in the outside world. Subjective criteria determine in how far an individual is willing to assimilate a particular meme.
Intersubjective criteria determine how easily memes travel from subject to subject.
The information in the genes of an organism constitutes its genotype. Its body, developed through the interaction of genotype with environment, constitutes its phenotype. The equivalent of a phenotype for memes is the sociotype , the concrete organization of the group of people carrying a collection of memes or memotype . For example, if the memotype is the whole of Mormon beliefs, then the sociotype is the group of all Mormons. The above review sketches the properties of memes in general, be they scientific theories, religions, musical styles or the use of gadgets.