Romantics everywhere may be happy to hear why the adage, “Smile and the whole world smiles with you,” holds true—at least according to a psychological study which proved just seeing a smile activates the muscles in our face that make that expression, even if we’re unaware of it. The psychologists further discovered that positive emotion words, such as “laugh” or “funny,” also influence our facial muscle activity, as well as our judgement.

In the experiment, volunteers were subliminally shown emotion verbs and adjectives while watching cartoons. Half of the participants held a pen to their lips to prevent them from smiling, while the remaining group did not have their facial muscles blocked. The results revealed that volunteers found cartoons to be funnier when they were preceded by smiling-related verbs rather than frowning-related verbs. More, those who had been free to smile while watching the cartoons judged them more positively.

Association for Psychological Science, 2009