"Putting paint on your face isn't always practical," he said. "This is just the way that I wanted to test this. But if you wanted to be covert, you could try we

"Putting paint on your face isn't always practical," he said. "This is just the way that I wanted to test this. But if you wanted to be covert, you could try wearing different styles of make-up or accessories. You could position a Band-aid on the right spot on your face. The power of this idea is that people can interpret it in their own way."