What’s in a smile? Encouragement? A friendly hello? A threat? It turns out that humans are fairly good at parsing the subtle signals sent in expressions like smiles, and those expressions and our perceptions of them can impact our body chemistry. In our March 15 show, Producer Will Cushman talks to Justin Martin, a graduate student in the UW-Madison Department of Psychology who conducts research in the Niedenthal Emotions Lab. Martin coauthored a paper that recently appeared in the journal Nature Scientific Reports that shows that different types of smiles can affect heart rates and the hormone cortisol. In their conversation, Martin explains the findings and describes the scientific study of emotions.