Every year in March, Brain Awareness Week champions the global campaign to celebrate and publicise the progress and benefits of brain research. Are you lying? Do you have a racial bias? Is your moral compass intact? To find out what you think or feel, we usually have to take your word for it. But questionnaires and other explicit measures to reveal what’s on your mind are imperfect: you may choose to hide your true beliefs or you may not even be aware of them.