Identifying Atypical Development

Atypical development refers to

the extremes of individual differences in development and can include both advanced and delayed trajectories.

Why is Atypical Development complex to define

Natural variation in development rates across children.

Variation in traits, strengths, and weaknesses across domains (e.g. cognitive, social, physical).

Principles considered when assessing Atypical Development

Developmental Domains

Normative Comparison

Contextual info

Individual Profiles

Developmental Regression

Developmental Domains

Cognitive

Adaptive Behaviour

Social Skills

Physical and Motor Skills

Normative Comparison

Use standardised tools to compare a child's performance with age-appropriate norms.

Individual Profiles

Identification of both strengths and weaknesses is essential — strengths may be relative rather than absolute.

Developmental Regression

Loss of previously acquired skills (common in ASC and ID) is a key red flag.

Wechsler Intelligence Scale for Children (WISC)

Assesses cognitive abilities

Age 6-16

Measures verbal comprehension, WM, processing speed

Vineland Adaptive Behaviour Scales

Semi-structures interview with caregiver

Children & Adults

Measures communication, daily living skills, socialisation, motor skills, maladaptive behaviour

Bayley-III

Early Developmental Screening

Age 1-42 months

Measures cog, language, motor, social-emotional, adaptive skills

Wechsler Nonverbal Scale

For non-verbal children

Age 4-21

Measures Nonverbal reasoning (visual tasks)

Leiter-R

Nonverbal cognitive test

Ages 3-75

Measures reasoning, attention, memory - ideal for ASC or hearing impediments

Standardised score

A standardised score is a converted value that tells you how a child's raw score compares to others of the same age or demographic.

accounts for variables such as age, sex, dev stage

Standardised Score Example

If a 10-year-old scores 45/160 in a reasoning task, that score alone is meaningless — but if the mean for 10-year-olds is 100, we can see it's far below average.

How is a standardised score expressed

Often expressed as t-scores, z-scores, or percentiles.

T-score: Mean = 50, SD = 10

Z-score: Mean = 0, SD = 1

Why are standardised scores important?

They remove bias caused by age or demographic differences.

What do standardised scores allow us to do?

Compare children fairly

Track strengths and weaknesses relative to a child's overall profile.

Determine whether a child is developing typically or atypically.

Make informed diagnoses and intervention plans.