Ideas cause ideas and help evolve new ideas. They interact with each other and with other mental forces in the same brain, in neighboring brains, and thanks to global communication, in far distant, foreign brains.

And they also interact with the external surroundings to produce in toto a burstwise advance in evolution that is far beyond anything to hit the evolutionary scene yet.
—  American neurophysiologist Roger Sperry, quoted by James Gleick, Smithsonian Magazine. What Defines a Meme?