This article is about the neural conundrum behind the slowness of human<br>behavior. The information throughput of a human being is about 10 bits/s. In<br>comparison, our sensory systems gather data at ~10^9 bits/s. The stark contrast<br>between these numbers remains unexplained and touches on fundamental aspects of<br>brain function: What neural substrate sets this speed limit on the pace of our<br>existence? Why does the brain need billions of neurons to process 10 bits/s?<br>Why can we only think about one thing at a time? The brain seems to operate in<br>two distinct modes: the "outer" brain handles fast high-dimensional sensory and<br>motor signals, whereas the "inner" brain processes the reduced few bits needed<br>to control behavior. Plausible explanations exist for the large neuron numbers<br>in the outer brain, but not for the inner brain, and we propose new research<br>directions to remedy this.