Bayley Scales of Infant and Toddler Development

The Bayley Scales of Infant and Toddler Development are a series of standardised tests designed to assess the developmental functioning of children from 1 to 42 months of age. Since the 1970s, they have been widely used by doctors and allied health professionals to identify infants and young children with developmental delays, to target and plan early intervention services, and to monitor a child’s progress. The Bayley Scales are also widely used as an outcome measure in epidemiological studies of the health and development of infants and young children and in clinical trials assessing the efficacy of early interventions. This entry describes the development of the Bayley Scales since their inception in the 1960s and the structure and content of the most recent editions of the test.