Pets have all the qualities necessary to be a virus of the mind:

- Pets penetrate our minds by attracting our attention. The quality they have that gets them attention is something like "cuteness" or "adorability."

- Pets actually program us to take care of them in several ways. The animals themselves take advantage of the instincts we have to care for our young. The pet industry, part of the pet virus, programs us through television and advertising to spend more and more money on expensive pet foods and veterinary bills.

- Pets are faithfully reproduced, with the help, of course, of their own DNA and of the resources we devote to caring for them. But there's also a tradition meme working for many pet species in the form of pet shows and kennel clubs. People are rewarded for reproducing a breed faithfully.

- And of course pets spread in the natural way. They do this so effectively that we've noticed the problem and started campaigns to neuter animals to prevent unwanted offspring. Of course, eliminating unwanted offspring also increases the value of the faithfully bred animals sold by the pet industry.

Pets evolved to be cuter and cuter. How? The ones that weren't cute-that weren't able to command our resources, to enslave us into taking care of them-they died! It's natural selection in action: the cute ones bred with each other until we reached the point we're at today ... infected with the pet virus.

Effective memes will be those that cause high fidelity, long-lasting memory. Memes may be successful at spreading largely because they are memorable rather than because they are important or useful. Wrong theories in science may spread simply because they are comprehensible and fit easilty with existing theories, and bad books may sell more copies because you can remember the title when you get to the bookshop -- though, of course, we do have strategies for overcoming these biases. An important task of memetics will be to integrate the psychology of memory with an understanding of memetic selection.

Some people argue that memes are not digital (Maynard Smith 1996) and that only digital systems can support evolution. Certainly genes are digital and certainly digital storage is far preferable to analogue. We all know that digital video- and audio-recordings look and sound better than their analogue predecessors; a digital system allows information to be stored and transmitted with far less loss of information even over noisy channels. However, there is no law that says that evolution has to be digitaly based -- the issue is really one of the quality of replication.

What, then, makes for a good quality replicator? Dawkins (1976) sums it up in three words -- fidelity, fecundity, and longevity. This means that a replicator has to be copied accurately, many copies must be made, and the copies must last a long time -- although there may be trade-offs between the three. Genes do well on all three counts, and being digital gives them high fidelity copying. So what about brains?