Validity and cross-cultural differences of the Bayley Scales of Infant and Toddler Development, Third Edition in typically developing infants

Background: The Dutch translation of Bayley Scales of Infant and Toddler Development, Third Edition (BayleyIII-NL) is a comprehensive tool assessing cognitive, language and motor development in children up to 42 months. Aims: The first aim of this study was to evaluate concurrent validity of the Bayley-III-NL Gross Motor Scale (GMS) in relation to the Alberta Infant Motor Scale (AIMS). Secondly, divergent validity between the other subscales mutually and the AIMS was investigated. Finally, the importance of population-specific reference values was examined. Methods and procedures: A sample of 122 healthy, typically developing Flemish children (mean age: 9 months 7 days), born full term was assessed with the Bayley-III-NL and the AIMS. Outcomes and results: Concurrent validity of the Bayley-III-NL GMS and the AIMS was moderate to high (0.59-0.98; p < 0.001). In addition, weak correlations (-0.10-0.27) between the non-motor-Bayley-III-NL subscales and the AIMS were found. Finally, significant differences were found between Bayley-III scores based on Flemish and American norms (p < 0.001), except for fine motor skills (p = 0.11). Conclusions and Implications: This study provides support for the concurrent validity of the Bayley-III-NL GMS and divergent validity of the different Bayley-III-NL subscales. Secondly, population-specific reference values should be used to avoid over- and under estimation of infant's development.