What makes a meme successful? Selection criteria
for cultural evolution
CLEA, Free University of Brussels, Pleinlaan 2, B-1050 Brussels,
To be published in: Proc. 15th Int. Congress on Cybernetics
(Association Internat. de Cybernétique, Namur).
ABSTRACT. 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.
Cultural evolution, including 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 (replicating) units of cultural
information: memes (Dawkins, 1976). A meme can be defined as an
information pattern, held in an individual's memory, which is capable of
being copied to another individual's memory. This includes anything that
can be learned or remembered: ideas, knowledge, habits, beliefs, skills,
images, etc. Memetics can then be defined as the theoretical and empirical
science that studies the replication, spread and evolution of memes (Moritz,
To be replicated, a meme must pass successfully through four subsequent
stages: 1) assimilation by an individual, who thereby becomes a host
of the meme; 2) retention in that individual's 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 by
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
meme relative to its competitors.
The four stages of meme replication
A 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 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 sufficiently salient to attract the host's 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 cognitive 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 unlikely 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.
The second stage of memetic replication is the retention of the meme in
memory. By definition, memes must remain some time in memory, otherwise
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 Dawkins's
(1976) longevity characteristic for replicators.
Just like assimilation, retention is characterized by strong selection,
which few memes will 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 remember 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 memory by frequent reinforcement.
To 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 common 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 expressed, 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 important that it must be
expressed again and again to everybody he or she meets.
To 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 transmit
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 vehicle.
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 multiplication,
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 since 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.
The overall survival rate of a meme m can be expressed as the meme
fitness F(m), which measures the 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, expression 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. E is the number of
times a retained meme is expressed by the host. T is the number
of copies of an expression that is transmitted to a potential new host.
Unlike A and R, E and T do not have an upper
bound, although E is likely to be more restricted than T.
Note that F is zero as soon as one of its components (A, R, E,
T) is zero. This expresses the fact that a meme must successfully pass
through all four stages in order to replicate. Also note that for
a meme to spread (F > 1), you must have E > 1 or T
General Selection Criteria for Memes
Which 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 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 mean 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. 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 using standard social science methodologies, e.g. for
developing test for personality traits.
Objective 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 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 that
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 subject's actions are also more likely to leave
a permanent memory trace.
Subjective criteria represent selection by the subject who assimilates
the meme. The main criteria at the assimilation stage are novelty
(facilitates assimilation by attracting the subject's attention) and simplicity
(requires less processing for the meme to be understood). The criterion
of coherence (connection, consistency and 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 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 making
it more worthwhile for the host to do the effort to assimilate.
Intersubjective 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 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 represent
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 hand, 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,
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.
Finally, 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" (cf. 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 (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 strengthen 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 rates of expression and transmission.
Table 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.
This simple four stage model helps us to analyse the mechanics of 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 selection criteria does produce a range of qualitative predictions,
which can be empirically tested.
Francis Heylighen has been supported during these investigations by the
Fund for Scientific Research - Flanders (FWO) as a Research Associate.
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