Bayleyskalaerne

Bayleyskalaerne are a set of standardized developmental assessment scales used to evaluate functioning in young children, typically from 1 month to 42 months. The scales were developed by Nancy Bayley in the 1960s as a means to measure developmental progress across multiple domains and are widely used in clinical, educational, and research settings. The original instrument led to several revisions, notably the Bayley Scales of Infant Development II (Bayley-II) and the Bayley Scales of Infant and Toddler Development III (Bayley-III). In many countries the Bayley-III remains common, with newer Bayley-4 editions introduced in some markets.

The Bayley scales comprise direct assessment tasks and caregiver-reported scales that yield standardized scores. The main scales assess Cognitive, Language (Receptive and Expressive), and Motor (Gross and Fine) development. In the Bayley-III, two additional scales—Social-Emotional and Adaptive Behavior—are completed via caregiver report, providing a broader view of development. Subtest and composite scores are normed to a representative sample, with a mean of 100 and a standard deviation of 15.

Administration and interpretation: Administered one-on-one by trained professionals in a private setting, often taking 30 to 90 minutes depending on age and cooperation. Test results are used to identify delays or deviant development, guide intervention planning, monitor progress, and support eligibility for services. Results should be interpreted in the context of medical history, culture, language exposure, and other assessments.

Limitations and considerations: Requires formal training and licensing for use, may be time-consuming, and normative data may not perfectly match every population, so cultural and linguistic factors should be considered.