VANCOUVER, CANADA — Researchers led by psychologist Gillian Sandstrom recruited 60 people outside a Starbucks in Vancouver, Canada, and randomly assigned them to either avoid small talk with staff or to engage socially with the barista. People who chatted with the barista were in a better mood and felt a greater sense of belonging than those who did not interact much with the staff.

Participants assigned to engage socially were instructed to make eye contact, smile, and have a genuine chat. Sandstrom, who works at the University of Sussex, designed the study to examine the benefits of brief social encounters with strangers, acquaintances, and others outside close social circles.

The Vancouver experiment built on earlier work. In a 2014 study, Sandstrom and colleagues recruited more than 50 participants and gave each two clicker counters to count interactions: one for strong ties and one for weak ties. Participants reported that days with more conversations with weak ties correlated with slightly higher happiness than days with fewer such interactions.

Much research on social connections has focused on people's closest relationships, while casual contacts with strangers and acquaintances can be beneficial to mental health. Social isolation increases the risk of premature death. "I think lots of people, if they think about it, can tell a story like that about a time where someone that they didn't know at all or didn't know well just really made a difference by listening or smiling or saying a couple of words," Sandstrom said.

Before becoming a psychologist, Sandstrom was a computer programmer. She later pursued a degree in psychology at Toronto Metropolitan University, where she was ten years older than her fellow students when she began her studies and initially did not feel like a part of the university community.

On her daily walk between university buildings, Sandstrom passed a hot dog stand and smiled and waved at the vendor, and the vendor smiled and waved back, although Sandstrom never bought a hot dog. She remembers feeling happier on days she saw the hot dog vendor and worse on days she did not see her.