“Can you hear me now?” “Is this you?” “Are you there?” If you’re asked a question like this in a normal conversation, it’s polite to let the other person know that you hear them loud and clear. But if ...

You pick up a call from a number you don’t recognize. The voice on the other end sounds a little garbled, a little uncertain. “Hello?” it says. “Can you hear me?” Your brain has already started ...