Don’t forget to smile…” were the words I heard as I left the house each day growing up. Maybe that’s why I’m a perennial optimist — or maybe it stems from how my frontal cortex works. Maybe optimism is a strength — maybe it’s a weakness. It’s one of many subjective lenses through which people view the world. These lenses have always fascinated me in literature, in life, and in psychological research. I explore these along with the lenses of stereotypes, prejudices, and self-concept. I’ve explored how these lenses develop and change, how they differ among people, how they underlie cooperation and conflict. They impact whether and how we care for each other and the rest of nature. They impact our own and others’ present and future well-being. They affect how we choose presidents and partners, how we are influenced by media, how we communicate… and whether we smile.