Developmental psychology is concerned with the changes that occur as humans move from infancy, to childhood, through adolescence, and on to adulthood. These changes include the development of thought processes, emotion, and social interactions. The National Institute of Child Health and Human Development study considered the issue and found that when the effects of home environment was controlled the influence of day care on peer relations was very small but was associated with less social competence. It is quite possible that children with an easy-going temperament are less likely to show behavioural problems, are socially competent, and get on better with other children. The behaviour of the main caregiver determines whether children are securely or insecurely attached. The hypothesis states that children have an innate need for a warm, continuous relationship. Controlled observations are particularly useful when researchers want to compare how different children respond in an identical situation.