For all its antiquity and constancy, touch is not passive or primitive or stuck in its ways. It is our most active sense, our means of seizing the world and experiencing it, quite literally, first hand. Susan J. Lederman, a professor of psychology at Queen’s University in Canada, pointed out that while we can perceive something visually or acoustically from a distance and without really trying, if we want to learn about something tactilely, we must make a move. We must rub the fabric, pet the cat, squeeze the Charmin. And with every touchy foray, Heisenberg’s Uncertainty Principle looms large. “Contact is a two-way street, and that’s not true for vision or audition,” Dr. Lederman said. “If you have a soft object and you squeeze it, you change its shape. The physical world reacts back.”