If Carl Sagan had been a neuroscientist instead of an astronomer, he might have mused wondrously about the “billions and billions” of neurons that make up the human brain. Approximately one hundred billion neurons with each neuron wired to communicate with thousands of neighbors. This massive mesh of computation gives rise to the impressive spectrum of human cognitive capabilities. To date, most HCI researchers have focused on readily observable behavioral metrics (e.g., the speed of a keystroke or the accuracy of a mouse click) rather than on the mental machinery operating under the surface. Modern neuroscience offers HCI researchers a way to “lift the veil” on user cognition, greatly expanding the available tool kit for both research and design…