Bayley Scales of Infant and Toddler Development

Original Editor - Romy Hageman
Top Contributors - Romy Hageman and Lauren Heydenrych

Introduction

The Bayley Scales of Infant and Toddler Development (BSID) is designed to assess and/or monitor very young children at risk of developmental delays or disorders. It provides an indication of the child's current developmental level and can also offer a cautious prognosis regarding expected development. The BSID stands out as the most frequently utilized instrument for assessing development during the initial two years of a child's life. The current version of the BSID is the third edition. It has proven to be a reliable diagnostic method for recognizing children with early developmental delays .

Objective

The primary purpose of the BSID is to evaluate various areas of a child's development to gain insight into their strengths and potential challenges.

The key objectives of using the BSID include:

• Early identification: Detecting developmental delays at an early age, allowing for timely intervention and support.
• Monitoring progress: Assessing developmental progress over time, particularly for children at risk of developmental delays or disorders.
• Research: Providing researchers and clinicians with a standardized measure for studying infant and toddler development across different populations.
• Intervention planning: Assisting in the development of targeted intervention plans for children with identified developmental concerns.
• Outcome measurement: Evaluating the effectiveness of interventions or treatments by comparing pre- and post-intervention developmental scores.

Intended population

Children at the age of 16 days - 42 months and 15 days.

Clinical indications for administration include:

• Prenatal complications and congenital disorders: such as brain malformation and anomalies.
• Neonatal complications: such as preterm birth and neonatal encephalopathy.
• Neurodevelopmental disorders: such as developmental disorders and Cerebral palsy.

Target examiner population: Physical therapists, Occupational therapists, Paediatricians, Research psychologists, Speech and language therapists, Neonatologists, early childhood specialists..

Method of use

The test BSID measures the following domains:

• Cognition
• Language (receptive and expressive language abilities)
• Motor skills (Fine and Gross motor skills)
• Socio-emotional behavior
• Adaptive behavior

Administration time

Time to administer the whole test:

• Children 0-6 months old: 30 minutes
• Children 6-12 months old: 50 minutes
• Children 13 months and above: 90 minutes

Time to administer only the motor skills:

• Children 0-6 months old: 10 minutes
• Children 6-12 months old: 20 minutes
• Children 13 months and above: 30 minutes

Administration procedure

The BSID is an observation list that must be administered in a specific order. Furthermore, administration of the BSID requires training.

Administration process

1. Preparation: before initiating the BSID, the therapist should familiarize themselves with the test components and ensure a suitable testing environment. This includes minimizing distractions and creating a comfortable setting to facilitate the child's engagement.
2. Introduction to tasks: Begin the assessment by introducing the tasks in a child-friendly manner, fostering a positive and cooperative atmosphere.
3. Sequential task administration: The BSID is structured to be administered in a specific order to maintain consistency and reliability. Follow the sequence of tasks, starting with the age-appropriate entry level.
4. Observation and scoring: During task administration, keen observation is essential. Note the child's responses, behaviors and any challenges encountered.
5. Collaboration with caregivers: Incorporate collaboration with caregivers throughout the assessment process. They can help the child to cooperate. It is important to instruct the caregiver to be encouraging, but not to interfere with their child's performance.
6. Documentation and reporting: Accurate documentation, scores, and any noteworthy behaviors is crucial. The therapist should use standardized forms and procedures for consistency.

The following video is an example of an administration of the BSID:

Scoring

Scores are derived by converting raw scores from completed tasks into scale scores and composite scores. These scores are then utilized to assess the child's performance in relation to norms established based on typically developing children of the same age. The BSID provides four variants of norm-referenced scores:

• Scaled subtest scores (range 1-19)
• Index scores (range: 40-160)
• Percentile scores (range: 0-100)
• Growth scores (range: 200-800)

The Bayley-III composite score is determined by comparing the child's performance to a normative age-matched sample defined by the assessment. Composite scores are calculated for the cognitive, language, and motor scales, and are interpreted as follows:

• Mean score of 100 (SD=15) at the 50th percentile signifies mid-average functioning.
• Scores below 85 (1 SD below the mean), at the 16th percentile, indicate mild impairment of being 'at risk' of developmental delay. Monitoring is recommended, along with advice to parents on techniques to enhance development or referral to a therapist based on the level of impairment.
• Score below 70 (2 SD below the mean), at the second percentile, indicate moderate to severe impairment.

In general, scores falling in the lowest 10th percentile indicate developmental delay. Children with scores in this range need additional assessment from the healthcare professional.

Evidence

The psychometric properties of the Bayley-III are:

• Test-retest:
  • 2-4 months (n=50): FM r=0.67: the correlation coefficient (r) for fine motor skills (FM) between the first and second test periods is 0.67. This indicates the extent to which children's fine motor performances are consistent in children aged 2-4 months. GM r=0.77: the correlation coefficient (r) for gross motor skills (GM) between the first and second test periods is 0.77. This indicates the extent to which children's gross motor performances are consistent in children aged 2-4 months.
  • 9-13 months (n=50): FM r=0.86: the correlation coefficient (r) for fine motor skills (FM) between the first and second test periods is 0.86. This indicates a strong level of consistency in fine motor performances in children aged 9-13 months between two measurement points. GM r=0.86: the correlation coefficient (r) for gross motor skills (GM) between the first and second test periods is 0.86. This suggests that gross motor performances in children aged 9-13 months are also remarkably consistent.
  • In both age groups, the high correlation coefficients indicate a significant level of agreement between the scores of the first and second test, indicating that the Bayley-III is reliable for measuring fine and gross motor skills in these age groups.
• Internal consistency:
  • 1-12 months old normal population (n=1700): FM r=0.77-0.89: the correlation coefficients for fine motor (FM) range from 0.77 to 0.89. This indicates how consistent the scores on different fine motor items are within the same testing period for the normal population of 1-12 months old children. GM r=0.86-0.94: the correlation coefficients for gross motor (GM) range from 0.86 to 0.94. This indicates how consistent the scores on different gross motor items are within the same testing periode for the normal population of 1-12 months old children.
  • 1-12 months old atypical population (n=688): FM r=0.90-0.92: the correlation coefficients for fine motor (FM) range from 0.90 to 0.92. This indicates how consistent the scores on different fine motor items are within the same testing periode for the atypical population of 1-12 months old children. GM r=0.93-0.96: the correlation coefficients for gross motor (GM) range from 0.93-0.96. This indicates how consistent the scores on different gross motor items are within the same testing period for the atypical population of 1-12 months old children.
  • Overall, the high correlation coefficients in both normal and atypical populations suggest strong consistency within the fine and gross motor subscales of the Bayley-III. This indicates that the items within each subscale reliably cohere, demonstrating the consistency and stability of measurements over time.
• Reliability: Fair
• Measurement error: Good
• Content validity: Excellent
• Structural validity: Good
• Criterion validity: Good
• Minimal detectable change: SEM gross motor subtest 0.85-1.08 of motor component =3.00-474 (24-42 months)

Criticisms of the BISID-III

Criticism of the Bayley-III often revolves around the duration required to administer the test. It can sometimes take too much time for families to set aside.

The Bayley-III is also seen as a somewhat broad assessment tool because it evaluates each developmental domain on a global level. Consequently, it might overlook specific abilities and subtle deficits within particular scales.

It has been observed that the Bayley-III tends to artificially increase scores in typically developing children while simultaneously underestimating developmental delay. In comparison to the earlier Bayley-II, children tend to achieve notably higher scores in the Bayley-III. This score inflation is partly attributed to inconsistencies in the normative sample and inaccuracies in administering the tool.

Strengths of the BSID-III

The Bayley-III is shown to be valid and reliable in different cultures after appropriate translation considering cultural, historical and social features: Vietnam, Suriname, Egypt and Russia.

The Bayley scales have been commonly employed in multiple countries, including the Netherlands, Iran, Australia, and various Asian countries.