Scientists in Sweden have figured out why it’s so difficult to keep a straight face if others around you are grinning away. It’s your unconscious mind taking control. The researchers at Uppsala University had volunteers look at pictures of expressionless, happy, and angry faces. In return they were told to adopt blank, happy, or angry expressions. When they had to meet a smile with a frown, or a frown with a smile, they had trouble. Twitching in the subjects’ faces — measured with electronic equipment — indicated they simply didn’t have control of their muscles. It’s believed that there’s a shortcut to the part of the brain that recognizes faces and expressions that bypasses the area responsible for conscious processing.