Bayley Scales of Infant Development (BSID)

Title of Assessment

Bayley Scales of Infant and Toddler Development, Fourth Edition (BSID‑4)

Author(s)

Nancy Bayley, PhD; updated by Glen P. Aylward, PhD, ABPP, et al.

Year of Publication / Publisher

2019; Pearson

Identify Type of Assessment

Standardized, norm-referenced developmental assessment for infants and toddlers 

Cost (identify source) & How to Access

• Complete kit (digital): ~$1,191.60
  
  

• Complete kit (print): ~$1,325.20
  
  

• Screening kit: available from ~$79.00
  Available through Pearson Clinical store online
  
  

Assessment (include link if possible)

Bayley-4 - Bayley Scales of Infant and Toddler Development | Fourth Edition | Pearson Assessments US 

Population

Children aged 16 days to 42 months (approximately 0 to ~3.5 years) 

Appropriate Settings

• Early intervention/home-based services
  
  

• Pediatric clinics and outpatient therapy
  
  

• Preschool or developmental follow-up clinics
  
  

• Research and clinical studies
  
  

Purpose of Assessment & Functions/Areas Assessed

To identify developmental delays, assist in planning interventions, and monitor developmental progress in infants and toddlers.
Assesses five domains:

• Cognitive
  
  

• Language (receptive & expressive)
  
  

• Motor (fine & gross)
  
  

• Social‑Emotional
  
  

• Adaptive Behavior 

Administration

• 30–70 minutes, depending on domains administered

• Administered individually; caregiver present but does not assist
  
  

• Scales can be administered separately or together
  
  

• Standardized instructions; available in print or via Pearson’s Q‑Global digital platform
  
  

User Qualifications

Qualified clinicians (e.g., psychologists, SLPs, OTs, developmental pediatricians) after completing Pearson-provided training

Materials Required

• Examiner manual
  
  

• Stimulus books and manipulatives
  
  

• Record forms or digital access via Q‑Global
  
  

• Online or paper scoring/reporting tools
  
  

Scoring Procedure

Responses scored 0/1/2, converted to raw, scaled, and composite scores; yields developmental quotients, percentiles, and age equivalents. Digital scoring available via Q‑Global

Psychometrics / Standardization

• Normed on national sample (updated for population changes)
  
  

• High reliability and validity; BSID‑4 shows improved sensitivity compared to earlier editions
  
  

Strengths & Weaknesses

Strengths

• Comprehensive coverage of five developmental domains
  
  

• Can administer individual domains flexibly
  
  

• Up-to-date norms & strong psychometrics
  
  

• Supports early identification & intervention planning
  
  

• Efficient digital administration and scoring
  
  

Weaknesses

• Costly initial investment
  
  

• Requires clinical training
  
  

• Administration time may be lengthy for full battery
  
  

• Caregiver proxy reports may introduce subjective bias