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1、What makes a meme successful? Selection criteria for cultural evolutionFrancis HEYLIGHENCLEA, Free University of Brussels, Pleinlaan 2, B-1050 Brussels, BelgiumE-mail: fheylighvub.ac.be,To be published in: Proc. 15th Int. Congress on Cybernetics (Association Internat. de Cyberntique, Namur). ABSTRAC
2、T. Meme replication is described as a 4-stage process, consisting of assimilation, retention, expression and transmission. The effect of different objective, subjective, intersubjective and meme-centered selection criteria on these different stages is discussed. IntroductionCultural evolution, inclu
3、ding the evolution of knowledge, can be modelled through the same basic principles of variation and selection that underlie biological evolution (Boyd & Richerson, 1985; Cavalli-Sforza & Feldman, 1981). This implies a shift from genes as (replicating) units of biological information to a new type of
4、 (replicating) units of cultural information: memes (Dawkins, 1976). A meme can be defined as an information pattern, held in an individuals memory, which is capable of being copied to another individuals memory. This includes anything that can be learned or remembered: ideas, knowledge, habits, bel
5、iefs, skills, images, etc. Memetics can then be defined as the theoretical and empirical science that studies the replication, spread and evolution of memes (Moritz, 1990). To be replicated, a meme must pass successfully through four subsequent stages: 1) assimilation by an individual, who thereby b
6、ecomes a host of the meme; 2) retention in that individuals memory; 3) expression by the individual in language, behavior or another form that can be perceived by others; 4) transmission of the thus created message or meme vehicle to one or more other individuals. This last stage is followed again b
7、y stage 1, thus closing the replication loop. At each stage there is selection, meaning that some memes will be eliminated. The present paper will look in more detail at the mechanisms governing these four stages, and present a list of selection criteria that allow us to estimate the fitness of a me
8、me relative to its competitors. The four stages of meme replicationAssimilationA successful meme must be able to infect a new host, that is, enter into its memory. Let us assume that a meme is presented to a potential new host. Presented means either that the individual encounters a meme vehicle, or
9、 that he or she independently discovers it, by observation of outside phenomena or by thought, i.e. recombination of existing cognitive elements. To be assimilated, the presented meme must be respectively noticed, understood and accepted by the host. Noticing requires that the meme vehicle be suffic
10、iently salient to attract the hosts attention. Understanding means that the host recognizes the meme as something that can be represented in his or her cognitive system. The mind is not a blank slate on which any idea can be impressed. To be understood, a new idea or phenomenon must connect to cogni
11、tive structures that are already available to the individual. Finally, a host that has understood a new idea must also be willing to believe it or to take it serious. For example, although you are likely to understand the proposition that your car was built by little green men from Mars, you are unl
12、ikely to accept that proposition without very strong evidence. Therefore, you will in general not memorize it, and the meme will not manage to infect you. RetentionThe second stage of memetic replication is the retention of the meme in memory. By definition, memes must remain some time in memory, ot
13、herwise they cannot be called memes. The longer the meme stays, the more opportunities it will have to spread further by infecting other hosts. This is Dawkinss (1976) longevity characteristic for replicators. Just like assimilation, retention is characterized by strong selection, which few memes wi
14、ll survive. Indeed, most of the things we hear, see or understand during the day are not stored in memory for longer than a few hours. Although you may have very clearly assimilated the news that the progressive liberal party won the Swaziland elections with 54% of the votes, you are unlikely to rem
15、ember anything of this a week later-unless you live in Swaziland, perhaps. Retention will depend on how important the idea is to you, and how often it is repeated, either by recurrent perception or by internal rehearsal. All learning paradigms agree that experiences are encoded more strongly into me
16、mory by frequent reinforcement. ExpressionTo be communicated to other individuals, a meme must emerge from its storage as memory pattern and enter into a physical shape that can be perceived by others. This process may be called expression. The most obvious means of expression is speech. Other commo
17、n means for meme expression are text, pictures, and behavior. Expression does not require the conscious decision of the host to communicate the meme. A meme can be expressed simply by the way somebody walks or manipulates an object, or by what he or she wears. Some retained memes will never be expre
18、ssed, for example because the host does not consider the meme interesting enough for others to know, uses it unconsciously without it showing up in his or her behavior, does not know how to express it, or wants to keep it secret. On the other hand, the host may be convinced that the meme is so impor
19、tant that it must be expressed again and again to everybody he or she meets. TransmissionTo reach another individual, an expression needs a physical carrier or medium which is sufficiently stable to transmit the expression without too much loss or deformation. Speech, for example, uses sound to tran
20、smit an expression, while text will be transmitted through ink on paper or electrical impulses in a wire. The expression will take the form of a physical signal, modulating the carrier into a specific shape from which the original meme can be re-derived. This physical shape may be called the meme ve
21、hicle. For example, meme vehicles can be books, photographs, artefacts or CD-ROMs. Selection at the transmission stage happens through either elimination of certain memes, when the vehicle is destroyed or gets corrupted before it is perceived by another individual, or through differential multiplica
22、tion, when the vehicle is reproduced into many copies. For example, a manuscript may be put into the shredder or it may be turned into a book which is printed in thousands of copies. A radio communication may get lost because of noise, or it may be broadcasted to millions of listeners. Especially si
23、nce the emergence of mass media, the transmission stage is the one where the contrast between successful and unsuccessful memes is largest, and where selection may have the largest impact. Meme fitnessThe overall survival rate of a meme m can be expressed as the meme fitness F(m), which measures the
24、 average number of memes at moment t divided by the average number of memes at the previous time step or generation t - 1. This fitness can be expressed in a simplified model as the product of the fitnesses or survival rates for each of the four stages, respectively assimilation A, retention R, expr
25、ession E and transmission T: F(m) = A(m) . R(m) . E(m) . T(m) A denotes the proportion of memes vehicles encountered (or memes independently discovered) by the host that are assimilated. R represents the proportion of these assimilated memes that are retained in memory. Therefore, A = 1, R 1), you m
26、ust have E 1 or T 1. General Selection Criteria for MemesWhich memes will most successfully pass all these stages can be modelled by a series of selection criteria. These criteria are discussed in more detail in earlier papers (Heylighen, 1993, 1997). I will here basically situate them with respect
27、to the four replication stages. The criteria can be grouped into different families, distinguished by the system responsible for the selection. At present, we have no method to derive the value of the fitness components from the degree to which a meme fulfils the different criteria. This does not me
28、an that no predictions can be made, though. All other things being equal, a meme that scores better on one of these criteria is predicted to become more numerous in the population than a meme that scores worse. This is a falsifiable hypothesis, which can be tested through experiments or observations
29、. For that, it suffices to operationalize the tested criterion. This has already been done for criteria such as invariance (Van Overwalle & Heylighen, 1995), formality (Heylighen & Dewaele, 1998) or conformity (cf. Boyd & Richerson, 1985), and seems relatively easy to do for the others as well by us
30、ing standard social science methodologies, e.g. for developing test for personality traits. Objective CriteriaObjective criteria denote selection by phenomena or objects independent of the hosts and memes involved in the process. The distinctiveness criterion functions mainly during the assimilation
31、 stage. It states that phenomena that are distinct, detailed or contrasted are more likely to be noticed and understood, and therefore assimilated. The invariance and controllability criteria, on the other hand, apply mainly to the retention stage. According to the invariance criterion, phenomena th
32、at recur, independently of the way in which they are perceived, are more likely to be maintained in memory. Controllability notes that phenomena which react differentially to the subjects actions are also more likely to leave a permanent memory trace. Subjective CriteriaSubjective criteria represent
33、 selection by the subject who assimilates the meme. The main criteria at the assimilation stage are novelty (facilitates assimilation by attracting the subjects attention) and simplicity (requires less processing for the meme to be understood). The criterion of coherence (connection, consistency and
34、 support between new perception and existing memory trace) facilitates the understanding and acceptance parts of the assimilation stage, since it represents the ease with which the new meme can fit in with the memory that is already there. It also facilitates the retention stage since memories that
35、cohere are more easy to retrieve and use and are therefore less likely to be forgotten. The criterion of utility, like controllability, functions mainly at the retention stage, since useful memes are more likely to be effectively used and thus reinforced, although it will also help assimilation, by
36、making it more worthwhile for the host to do the effort to assimilate. Intersubjective CriteriaIntersubjective criteria represent selection through the interactions between different subjects. Group utility is an emergent criterion, that is implicit in all four stages: a memes that is useful to the
37、group of all its hosts is more likely to survive because it helps the group itself to survive and grow, and thus to absorb other individuals. Authority functions mainly at the assimilation stage: memes from authoritative sources, i.e. hosts or vehicles that are held in high regard or considered to r
38、epresent expertise in the domain, will be more easily noticed and accepted. Formality (i.e. precise, unambiguous expression) too helps assimilation, at least of the original memetic content of the expression. It will contribute basically to what Dawkins (1976) calls copying-fidelity. (On the other h
39、and, informal expression, because it tends to be simpler, may facilitate assimilation, but of an idea different from the one initially expressed). Conformity, the reinforcement of the same meme by different hosts belonging to the same group, will boost acceptance and retention (cf. Boyd & Richerson,
40、 1985). Expressivity, the ease with which the meme can be expressed in an intersubjective medium, will obviously contribute to the expression stage. Publicity, finally, the effort put by the host(s) into the broad distribution of the message, will maximize transmission. Meme-centered CriteriaFinally
41、, the meme-centered criteria represent selection on the level of the meme itself. They depend only on the internal structure of the meme, not on its fit to external selectors, such as subjects, objects, or groups. These criteria will typically select for selfish (cf. Heylighen, 1992) or parasitic (c
42、f. Cullen, 1998) memes, whose only goal is to spread themselves, infecting a maximum of hosts without regard for their hosts well-being. This does not imply that the same meme cannot satisfy both selfish and non-selfish criteria. Religions often have this mixture of parasitic and beneficial traits (
43、cf. Cullen, 1998) Self-justification, the degree to which the components of a meme mutually support each other, will facilitate understanding and acceptance. Self-reinforcement, the degree to which the meme stimulates its host to rehearse itself, e.g. by repetition, meditation, prayer, etc., will st
44、rengthen retention. Intolerance, the degree to which a meme excludes rival memes from being assimilated or retained, will also help the meme to retain a stable position in memory. Proselytism, the degree to which the meme urges its host to maximally spread the meme to other hosts, will increase the
45、rates of expression and transmission. stagesselectorsObjectiveSubjectiveInter-subjectiveMeme-centeredAssimilationdistinctivenessnovelty simplicity coherenceauthority formalityself-justificationRetentioninvariance controllabilitycoherence utilityconformityself-reinforcement intoleranceExpressionexpre
46、ssivityproselytismTransmissionpublicityproselytismTable 1: a summary of the main selection criteria for memes, classified according to the stage during which they are most active, and the system responsible for the selection. ConclusionThis simple four stage model helps us to analyse the mechanics o
47、f meme replication, and the different requirements a meme must satisfy to spread successfully. It moreover helps us to situate and to systematize a more intuitively developed list of objective, subjective, intersubjective and meme-centered selection criteria. Although the four stage model suggests a formula for calculating memetic fitness, the theory is as yet insufficiently developed to unambiguously determine the parameters of the equation. However, the list of selec
