I've read some memetic algorithms papers, but I never read this one. You did me a favour by pointing to the right section among the 68 pages :)
Now, I don't deny that Moscato and other MA people were inspired by memetics and Dawkins. What I'm saying is the difference between GAs and MAs fails to correspond to the difference between genes and memes. I'm not alone: p. 19 says "The GA community would like to say that MA are only a special kind of GA with local hill-climbing." That is what I said before.
The essential difference between MAs and GAs is the extra local search. This is supposed to be analogous to the ability of a martial arts master to make not random changes to his/her memes (genetic mutations are random), but directed changes. There are two problems with this:
In MAs, the hill-climbing does, in all cases I have seen, boil down to using random mutations and discarding the bad ones. (How else would we do hill-climbing, on a black-box fitness function?) So the changes are not really directed any more than GA mutations are directed, when the GA uses selection.
I think there is a lot more to the idea of memes than just directed changes. What about their non-particulate nature, in Dawkins' phrase? That has no analogue in MAs that is not already in GAs. What about their weird method of combination, which is more like compounding than crossover? That has no analogue in MAs, as far as I know.
Are there some other features that distinguish MAs from GAs? Moscato mentions non-"genetic" representations, meaning non-linear ones. That has been common in GAs for a long time. I use tree-based, grammatical, and real-valued representations all the time. Even if (using the example in the paper) two-dimensional representations were common in MAs and unheard of in GAs, memes are not more accurately represented by matrices of bits than they are by lists of bits. Neither representation is adequate for the almost unrepresentable space occupied by memes.
Any other distinguishing features? Cooperative versus competitive coevolution (p 20)? Common in GAs, and more importantly, common in real-world genetic evolution.
EDIT: added to second-last paragraph.
The essential difference between MAs and GAs is the extra local search. This is supposed to be analogous to the ability of a martial arts master to make not random changes to his/her memes (genetic mutations are random), but directed changes. There are two problems with this:
In MAs, the hill-climbing does, in all cases I have seen, boil down to using random mutations and discarding the bad ones. (How else would we do hill-climbing, on a black-box fitness function?)
That is an easy question. A "black-box fitness function" doesn't mean the funct...
"All models are wrong, but some are useful" — George E. P. Box
As a student of linguistics, I’ve run into the idea of a meme quite a lot. I’ve even looked into some of the proposed mathematical models for how they transmit across generations.
And it certainly is a compelling idea, not least because the potential for modeling cultural evolution alone is incredible. But while I was researching the idea (and admittedly, this was some time ago; I could well be out of date) I never once saw a test of the model. Oh, there were several proposed applications, and a few people were playing around with models borrowed from population genetics, but I saw no proof of concept.
This became more of a problem when I tried to make the idea pay rent. I don’t think anyone disputes that ideas, behaviors, etc. are transmitted across and within generations, or that these ideas, behaviors, etc. change over time. As I understand it, though, memetics argues that these ideas and behaviors change over time in a pattern analogous to the way that genes change.
The most obvious problem with this is that genes can be broken down into discrete units. What’s the fundamental unit of an idea? Of course, in a sense, we could think of the idea as discrete, if we look at the neural pattern it’s being stored as. This exact pattern is not necessarily transmitted through whatever channel(s) you’re using to communicate it — the pattern that forms in someone else’s brain could be different. But having a mechanism of reproduction isn’t so important as showing a pattern to the results of that reproduction: after all, Darwin had no mechanism, and yet we think of him as one of the key figures in discovering evolution.
But I haven’t seen evidence for the assertion that memes change through time like genes. I have seen anecdotes and examples of ideas and behaviors that have spread through a culture, but no evidence that the pattern is the same. I haven’t even seen a clear way of identifying a meme, observing it’s reproduction, or tracking its offspring. Not so much as a study on the change of frequency of memes in an isolated population. Memetics today has less evidence than Darwin did when he started out; at least Darwin could point to discrete entities that were changing.
Without this sort of evidence, all the concept of a meme gives me is that ideas and behaviors can get transmitted, and that they can change. And I don’t need a new concept for that. Every now and then I’ll run a search on memetics just to see if anyone’s tried to address these problems — after all, a model describing how the frequency of ideas change in a population could be extremely useful to me — but so far I’ve seen nothing, and I don’t usually have the time to run a truly thorough search.
If any of you have, and if you know of evidence for the concept, please send me a link.