The Block and Block Longitudinal Study examined personality and cognitive development from childhood to early adulthood for a sample of 128 children. In particular, the study sought to investigate the concepts of ego-control and ego-resiliency. Ego control refers to the delaying of behavioral impulses; undercontrollers tend to act more spontaneously, while overcontrollers are more constrained. Ego resiliency refers to a person's ability to moderate their level of ego control to fit a particular situation. Children were assessed at ages 3, 4, 5, 7, 11, 14, 18, 23, and 32; data collection began in 1969 and concluded in 1999. A wide variety of data were collected, including school and demographic information; evaluations by teachers, parents, and observers; standardized psychological tests; and self-report questionnaires.
Participants were selected from two consecutive cohorts at two nursery schools in Berkeley, California. Although not selected to be representative of a national population, the sample was varied in terms of social class and parent educational level. Upper- and middle-class children are somewhat over-represented.