Studies of consciousness often run into a common conundrum of science — it’s hard to measure a system without the measurement affecting the system. Researchers assessing consciousness, for instance as volunteers receive anesthesia, typically use spoken commands to see if subjects can still respond, but that sound might keep them awake longer or wake them up sooner than normal. A new study not only validates a way to assess consciousness without external stimulation, it also finds that it may be more precise. “We want to measure when people make the…