A meme is "an idea, behavior or style that spreads from person to person within a culture." A meme acts as a unit for carrying cultural ideas, symbols or practices, which can be transmitted from one mind to another through writing, speech, gestures, rituals or other imitable phenomena. Supporters of the concept regard memes as cultural analogues to genes in that they self-replicate, mutate and respond to selective pressures. The word meme is a shortening of mimeme and it was coined by the British evolutionary biologist Richard Dawkins in The Selfish Gene as a concept for discussion of evolutionary principles in explaining the spread of ideas and cultural phenomena.
Examples of memes given in the book included melodies, catch-phrases, fashion and the technology of building arches. Proponents theorize that memes may evolve by natural selection in a manner analogous to that of biological evolution. Memes do this through the processes of variation, mutation, competition and inheritance, each of which influences a meme's reproductive success. Memes spread through the behavior that they generate in their hosts. Memes that propagate less prolifically may become extinct, while others may survive, spread and mutate.
Memes that replicate most effectively enjoy more success, and some may replicate effectively even when they prove to be detrimental to the welfare of their hosts. A field of study called memetics arose in the 1990s to explore the concepts and transmission of memes in terms of an evolutionary model. Criticism from a variety of fronts has challenged the notion that academic study can examine memes empirically. However, developments in neuroimaging may make empirical study possible. Some commentators in the social sciences question the idea that one can meaningfully categorize culture in terms of discrete units, and are especially critical of the biological nature of the theory's underpinnings others, including Dawkins himself, have argued that this usage of the term is the result of a misunderstanding of the original proposal.