A range of techniques are used to recruit families for studies in developmental psychology. Table 1 provides some examples. In developmental psychology, it is important to acknowledge that there are many differences in the families in which children are raised. Often samples do not include families from more unusual circumstances unless they are the specific population of interest. For example,  older couples, single parents (where children do and do not see both parents regularly), children of imprisoned parents or those from travelling families with no fixed address. When children from these groups are under-studied, psychology fails to understand their differing needs.