Child Study Center, School of Medicine, Yale University, records concerning the longitudinal study

The Yale longitudinal study was planned as an ambitious exploratory study of personality (ego) development in the first years of life. The research team was composed of pediatricians, child psychologists, nursery-school teachers, psychiatric social workers and psychoanalysts, specialists in early childhood development. The initial investigators, including Ernst Kris, Sally Provence, then-director Milton Senn, Charlotte del Solar and Katherine Wolf, began to recruit families and pilot the data collecting apparatus in early 1950.

Potential subjects were approached after their first obstetrical contact at the Yale-New Haven Hospital. Mothers were recruited if they were white, married, between eigthteen and thirty-five years, expecting their first child, presenting no severe physical or mental health complaints, expecting to reside in the vicinity of New Haven for several years, and if they expressed interest in participation.

Twenty-two families were initially recruited. Eventually ten families were followed completely, and there are also records for another six discontinued subjects. The collection of data for the study proper began in 1950. In its original conception the children were to be followed from birth through their first five years of life, but as the study progressed some subjects continued to be followed well into their teenage years.