One of the first tests was devised by the pioneering pediatrician and child psychologist Arnold L. Gesell (1880-1961). Gesell founded the Clinic of Child Development at Yale in 1911 and directed it for many years. He observed infants and young children, filmed them, analyzed their functioning frame-by-frame, and learned the normal stages in early human behavioral development. His test is formally called "the Gesell developmental schedule." Since his studies, a number of other behavioral assessments have been established for children. These include:
- The Neonatal Behavioral Assessment Scale (NBAS), better known as "the Brazelton" (because it was devised by the Harvard pediatrician T. Berry Brazelton);
- The Denver Developmental Screening Test (DDST) for children 0-6 years of age;
- The ELM (Early Language Milestone) scale for children 0-3 years of age;
- The CAT (Clinical Adaptive Test) and CLAMS (Clinical Linguistic and Auditory Milestone Scale) for children 0-3 years of age;
- The Infant Monitoring System for children aged 4-36 months;
- The Early Screening Inventory for children 3-6 years of age; and
- The Peabody Picture Vocabulary Test ("the Peabody") for testing children 2 1/2 to 4 years of age.
The purposes of developmental assessment depend on the age of the child. For a newborn, testing may detect neurologic problems, such as cerebral palsy. For an infant, testing often serves to reassure parents or to identify the nature of problems early enough hopefully to treat them. Later in childhood, testing can help delineate academic and social problems, again, hopefully in time to remedy them.