The Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4) is a gold-standard tool used by early childhood professionals to assess the developmental progress of young children. It provides a detailed picture of a child’s strengths and areas for support across five key domains:

Cognitive – problem-solving, attention, and memory

Language – receptive and expressive communication

Motor – fine and gross motor skills

Social–Emotional – social engagement and emotional regulation

Adaptive Behavior – practical, everyday skills for independence

How Is It Used?

The Bayley-4 is typically administered in a one-on-one setting by a trained professional such as a developmental specialist, psychologist, or early interventionist. It takes approximately 30 to 70 minutes, depending on the child’s age. The assessment uses engaging, play-based tasks and caregiver input to gather a well-rounded view of the child’s development. Results are scored using standardized norms and include: Scaled scores and composite scores Percentile ranks Developmental age equivalents Growth scale values These insights help guide early intervention planning, monitor developmental progress, and support families in understanding their child’s unique profile.

Who Created the Bayley-4?

The Bayley-4 was developed by Nancy Bayley, PhD, a pioneering psychologist in child development, and Glen P. Aylward, PhD, ABPP, a clinical psychologist with expertise in pediatric neurodevelopment.

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