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The Bayley Scales of Infant Development. II: Where to start?
S M Gauthier1, C R Bauer, D S Messinger
1Department of Pediatrics, University of Miami School of Medicine, Florida 33101, USA.
Insights
Starting the Bayley Scales of Infant Development-Second Edition (Bayley II) assessment with different item sets significantly impacts infant Mental Developmental Index (MDI) scores. Minor administration changes affect eligibility for crucial follow-up services.
Area of Science:
- Developmental Psychology
- Pediatric Neurodevelopmental Assessment
Background:
- The Bayley Scales of Infant Development-Second Edition (Bayley II) is a widely used tool for assessing infant development.
- Standardized administration protocols are crucial for reliable and valid developmental assessments.
Purpose of the Study:
- To investigate the impact of varying the starting item set on Bayley II Mental Scale scores.
- To determine if initial item set selection influences the Mental Developmental Index (MDI) and subsequent referability decisions.
Main Methods:
- Administered the Bayley II Mental Scale to 78 12-month-old infants, using 11-, 12-, and 13-month age item sets as starting points.
- Calculated three separate MDI scores for each infant based on the different starting item sets, using 12-month norms.
- Assessed the impact of score variations on the proportion of infants receiving below-normal MDI scores (< 85).
Main Results:
- MDI scores were significantly lower when starting with the 11-month item set compared to the 12-month set, and lower still compared to the 13-month set.
- Using the 11-month item set as the starting point resulted in twice as many infants scoring below normal (< 85 MDI).
- These score variations can significantly affect decisions regarding infant eligibility for follow-up services.
Conclusions:
- The choice of the initial item set in Bayley II administration significantly influences infant MDI scores.
- Standardized administration, without assumptions about an infant's current functioning, is essential to minimize score variability.
- Adherence to standardized protocols ensures accurate assessment and appropriate referrals for developmental support.
Abstract:
This study examines whether the Bayley Scales of Infant Development-Second Edition (Bayley II) Mental Scale scores vary on the basis of which item set is considered the starting point of an infant's assessment. The Bayley II was administered to 78 12-month-old infants by certified examiners beginning with the 12-month age item set. A second certified examiner then administered 10 additional items that completed the 11-month and 13-month age item sets. Of the 78 infants tested, 73 (94%) met basal and ceiling criteria in all three item sets. Three separate Mental Developmental Index (MDI) scores were calculated using 12-month norms for each subject, which were based on the raw scores generated from the 11-, 12-, and 13-month age item sets. Scores calculated on the 11-month set were significantly lower than those on the 12-month set, which were in turn significantly lower than those on the 13-month set. When tested on the 11-month instead of on the 12-month item set, twice as many infants received lower than normal (< 85) MDI scores, indicating an impact on referability decisions. Minor adjustments in administration of the Bayley II, such as those based on assumptions regarding an infant's current level of functioning, significantly affect infant test scores and eligibility for follow-up services. Standardized use of this test should minimize variability in test scores.