Mediation and technologies of mediation, whether the sign (Vygotsky), the symbol (Piaget), or the mirror or signifier (Lacan), all play central roles in accounts of human development and activity. They are not simply metaphors enabling, say, a particular conception of memory, perception or language -- as is the case for Plato's wax tablet, Descartes' camera obscura or Chomsky's computational "language organ." Instead, media form the organizing principles for the psyche and its functions overall; they provide the pivotal moment for maturation and humanization -- the point where human development allegedly diverges decisively from the animal to the human. But in these contexts, media are not simply the basis, cause or source of psychological phenomena; they are inextricable from and in a sense even constitutive of them.

In the wake of the controversy that greeted his paper, Everett encouraged scholars to come to the Amazon and observe the Pirahã for themselves. The first person to take him up on the offer was a forty-three-year-old American evolutionary biologist named Tecumseh Fitch, who in 2002 co-authored an important paper with Chomsky and Marc Hauser, an evolutionary psychologist and biologist at Harvard, on recursion. Fitch and his cousin Bill, a sommelier based in Paris, were due to arrive by floatplane in the Pirahã village a couple of hours after Everett and I did. As the plane landed on the water, the Pirahã, who had gathered at the river, began to cheer. The two men stepped from the cockpit, Fitch toting a laptop computer into which he had programmed a week’s worth of linguistic experiments that he intended to perform on the Pirahã. They were quickly surrounded by curious tribe members. The Fitch cousins, having travelled widely together to remote parts of the world, believed that they knew