Good metaphors can help understanding complex systems. The brain-computer metaphor arguably started when McCulloch and Pitts (1943) put together the idea of an artificial computational neuron with multiple inputs, either inhibitory or excitatory, a single branching output and a threshold for firing, proving that in principle a neural network made of these logical neurons could carry out very general computations. This meant that the brain could be treated as a computer and the neuron as its basic switching element. Research in cognitive neuroscience has ever since revealed many important differences between brains and computers, so that the brain-computer metaphor has gone through difficult days.