Woman Smiling in Field of Sunflowers (IMAGE) University of South Australia Caption When your muscles say you're happy, you're more likely to see the world around you in a positive way. Credit Unsplash Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.