The Bayley Scales of Infant Development
The Bayley Scales of Infant Development (BSID) have been used extensively worldwide to assess the development of infants. The test is given on an individual basis and takes 45-60 minutes to complete. It is administered by examiners specifically trained in BSID test procedures. The examiner presents a series of test materials to the child and observes the child’s responses and behaviours. The test contains items designed to identify young children at risk for developmental delay. BSID evaluates individuals along three scales:
- Mental scale: This part of the evaluation, which yields a score called the mental development index, evaluates several types of abilities: sensory/perceptual acuities, discriminations, and response; acquisition of object constancy; memory learning and problem solving; vocalisation and beginning of verbal communication; basis of abstract thinking; habituation; mental mapping; complex language; and mathematical concept formation.
- Motor scale: This part of the BSID assesses the degree of body control, large muscle coordination, finer manipulative skills of the hands and fingers, dynamic movement, postural imitation, and the ability to recognise objects by sense of touch (stereognosis).
- Behaviour rating scale: This scale provides information that can be used to supplement information gained from the mental and motor scales. This 30 item scale rates the child’s relevant behaviours and measures attention/arousal, orientation/engagement, emotional regulation and motor quality.
The BSID are known to have high reliability and validity. The mental and motor scales have high correlation coefficients (.83 and .77 respectively) for test-retest reliability.
