In the new experiment, roosters made fewer alarm calls, meant to warn peers of predators, when placed in front a mirror versus when standing near another rooster. Stefano Spaziani / picture alliance ...

In a hall of mirrors, you can see yourself stretched, squashed and multiplied thanks to the reflective physics of mirrors. One mirror reflects onto another, which reflects onto another, and so on. It ...

Daniel Povinelli was in high school when he first read about a clever experiment, published in 1970, that showed chimpanzees—but not monkeys--can recognize themselves in mirrors. "I bought into the ...