[3] Prior to the first official scale by Nancy Bayley, research was conducted to determine which important variables should be included in a cumulative developmental test for infants.
In 1965, Nancy Bayley conducted an experiment examining mental and motor test scores for infants aged 1 to 15 months, comparing sex, birth order, race, geographical location, and parental education.
[7] Researchers assessed the predictive validity of the BSID-II Mental Development Index (MDI) for cognitive function at school age for infants born with extremely low birth weight (ELBW).
[8] It was found that the predictive validity of a subnormal MDI for cognitive function at school age is poor but better for ELBW children who have neurosensory impairments.
[8] This brought on concern that decisions to provide intensive care for ELBW infants in the delivery room might be biased because of reported high rates of cognitive impairments.
[2] Considering that the primary intent of the Bayley-III is to identify children experiencing developmental delay and not to specifically diagnose a disorder, the floor and ceiling of the subtest and total test appear to be adequate.
[10] 1477 preterm infants born at <26 weeks gestation completed an 18-month neurodevelopmental follow-up assessment including the Receptive and Expressive Language Subscales of the BSID-III.
[10] Another more recent study focused on how the application of the BSID-III was useful in recommending treatments for infants in a Neo-natal Intensive Care Unit follow-up clinic.