A team of European scientists is using arithmetic problems to give conscious but paralyzed people a way to respond to yes-or-no questions.
The key is that exertion of mental effort causes pupils to dilate. A patient is shown a problem—45 x 34, say—and instructed to attempt to calculate the product only when the answer to the question posed—"Are you 20 years old?" perhaps—is "yes."
Communication via math-induced pupil dilation is cheaper and easier than the alternatives currently available, researchers say.
Read New Scientist's coverage.