Page Last Updated: May 15, 2026

Bayley-4🔗

Bayley Scales of Infant and Toddler Development, Fourth Edition

Table Name	`ncl_ch_bayley`
Construct	Child Development (Cognitive, Language, and Motor)
Study Visits	V04
Administration	Child-specific: Yes Respondent: Child Method: HBCD Study staff in person (60-90 min estimated duration)
Quality Control	HBCD Study staff were trained and certified by experienced Bayley administrators to ensure adherence to standardized procedures. During testing, responses were entered into QGlobal (Pearson’s official scoring platform for the Bayley Scales), which automatically applied scoring rules and generated standardized scores. Data underwent quality checks at both the individual and cohort levels, including range and consistency checks, to identify potential errors or deviations. Completion rates were monitored across sites, with additional training provided when needed.

Performance of the Bayley Scales of Infant and Toddler Development, Fourth Edition, reflects the child's developmental status, but various factors might influence the results of the assessment that should be taken into account.

The test was given in the context of a battery of tests and procedures administered to the child and his/her caregiver during the course of an extended visit. Some children may experience fatigue from this and this may have adversely impacted their performance. Ratings of arousal level of the child before and after the assessment may help in identifying situations where the child may have under-performed.

The child's exposure to different languages may also impact their performance. The Multilingual Language Development questionnaire was used to screen for parental preference for the test to be administered in Spanish or English (Spanish language translations used are available upon request). The instrument also documents other language exposures that the child may have. Exposure to languages other than Spanish or English may impact a child's performance. In addition, some items on the test may be impacted by environmental experiences related to the task or items used. In these cases, the test may underestimate the child's developmental status.

Missing Records
A subset of participants are missing the Bayley-4 records, i.e. the Administration field (ncl_ch_bayley_administration) has a value of 'None.' However, there are a variety of reasons why the data may be missing, therefore a value of 'None' does not mean that the Bayley was not administered. These data will be added in future releases as it becomes available.

Limited Predictive Validity for Long-Term Neurocognitive Status
Although the Bayley Scales of Infant and Toddler Development, Fourth Edition, is a well-established and validated measure of infant development, tests of this nature have historically had limited predictive validity for long-term neurocognitive status.

Invalid Scores for Subset of Participants
Participants may include invalid sub-test and/or domain scores of -9999. Users should remove this participant data prior to analysis.

Instrument Details🔗

The Bayley Scales of Infant and Toddler Development, Fourth Edition, is an established, commercially available measure of early development. The test provides an estimate of the child's cognitive, language, and motor skills. The Language Domain evaluates both receptive and expressive communication skills. The Motor Domain evaluates both fine and gross motor skills. The Social-Emotional and Adaptive Behavior Scales of the Bayley-4 were not administered in this study. Publisher documentation for the Bayley-4 is available here.

Administration
The test was designed to be administered by trained clinicians. For the HBCD Study, however, administration was performed primarily by trained Research Assistants (RAs). HBCD implemented a rigorous training and certification process to ensure that all RAs met study-wide standards before conducting assessments. For training, subject matter experts (licensed psychologists with expertise in infant testing and BSID-4 administration) provided lectures, group discussions, and office hours for individualized guidance. To be certified, RAs were required to submit both a recorded administration and their QGlobal item-level scoring for expert review.

Use of Caregiver Questions
The use of Caregiver Questions on the BSID-4 was modified. RAs were instructed to query the caregiver if the child scored below a 2 on items where caregiver input is permitted to inform the assessment. The BSID-4 manual specifies using caregiver reports when the target behavior “has not been observed.” It also notes that caregiver questions were used in 95% of administrations in the normative sample, with no formal limit on their use. The manual indicates that the assessment’s validity may be questioned if there are frequent discrepancies between what is observed and what is reported.

Accommodations For Spanish-Speaking Households
Modifications were made to accommodate Spanish-speaking households. English instructions were translated by experienced Bayley assessors accustomed to administering the BSID-4 in Spanish contexts for infants. The HBCD Spanish Language Committee reviewed translations, resolving discrepancies through iterative discussion. For families opting for Spanish administration, RAs used the approved HBCD Spanish translations of both instructions and caregiver questions. No modifications were made to the scoring of the responses and computation of the associated cluster and standard scores.

Bayley scores are generated automatically using QGlobal, Pearson’s official scoring platform for the Bayley Scales. Scores reflect the standardized scoring procedures implemented by Pearson, and no additional manual scoring or modification is applied.

References🔗

Bayley, N., & Aylward, G. (2019). Administration Manual: Bayley Scales Infant Toddler Development, Fourth Edition. Pearson.