Bayley Scales of Infant Development

The Bayley Scales of Infant Development is a standard series of measurements, first developed by Nancy Bayley, used to assess the fine and gross motor skills, receptive and expressive language, and cognitive development in infants and toddlers to the age of three. Now in its third edition (Bayley III), the Bayley Scales of Infant Development (BSID) describes the developmental function of infants, and is generally used to assist in the diagnosis and treatment of those identified as having developmental delays or disabilities.

The test must be administered individually, and generally takes between 45 and 60 minutes for completion. Only individuals who are experienced clinicians, with specialized training in the Bayley Scales of Infant Development should administer the test. Together, there are three separate scales: mental, motor, and behavior.

The mental scale evaluates sensory/perceptual acuities, discriminations, the acquisition of object constancy, problem solving, verbal communication and mathematical concept formulation. The motor scale portion assesses the degree of bodily control, muscle coordination, fine motor skills, and the ability to recognize objects through the sense of touch. The behavior portion rates the child's relevant behaviors, such as emotional regulation. Overall, the Bayley Scales of Infant Development is known to be a highly reliable test.