The Medical Research Council National Survey of Health and Development (NSHD) is Britain’s longest-running birth cohort study. From their birth in 1946 until the present day, its research participants, or study members, have filled out questionnaires and completed cognitive or physical examinations every few years. Among other outcomes, the findings of these studies have framed how we understand health inequalities. Throughout the decades and multiple follow-up studies, each year the study members have received a birthday card from the survey staff. (...) Although the birthday cards were originally produced in 1962 as a method to record changes of address at a time when the adolescent study members were potentially leaving school and home, they have become more than that with time. The cards mark, and have helped create, an ongoing evolving relationship between the NSHD and the surveyed study members, eventually coming to represent a relationship between the study members themselves. This article uses the birthday cards alongside archival material from the NSHD and oral history interviews with survey staff to trace the history of the growing awareness of importance of emotion within British social science research communities over the course of the 20th and early 21st centuries. It documents changing attitudes to science’s dependence on research participants, their well-being, and the collaborative nature of scientific research. The article deploys an intertextual approach to reading these texts alongside an attention to emotional communities drawing on the work of Barbara Rosenwein. (shrink)