At What Age Is the CDI Used for a Child?

A simple parent-report checklist that captures your toddler's first words and gestures — that is the CDI.

In short

The MacArthur–Bates Communicative Development Inventories (CDI) are parent-completed questionnaires used to understand early communication in young children, typically from around 8 months to 30 months (roughly 2.5 years) of age. They come in two main forms — Words and Gestures for infants of about 8–18 months, and Words and Sentences for toddlers of about 16–30 months. Because parents know their child best, the CDI draws on your everyday observations to map vocabulary, gestures and early sentence-building.

How the CDI is used

The CDI is not a test your child sits — it is a checklist you complete about the words your child understands and says, the gestures they use (like pointing or waving), and, for older toddlers, how they begin combining words. The Words and Gestures form suits infants from around 8 to 18 months, when communication is mostly understanding, babbling and gesturing. The Words and Sentences form suits toddlers from around 16 to 30 months, when spoken vocabulary grows quickly and short phrases appear. There are also short forms and extensions used in research and screening. Because early language varies widely between children, the CDI is best read as one helpful snapshot — a starting point for a conversation, not a verdict on your child's abilities.

When to seek a review

If your toddler is using far fewer words than other children their age, is not pointing or gesturing by around 12–15 months, or is not combining two words by around 24 months, a gentle developmental review is worthwhile. Early support for communication is playful and effective, and noticing a gap early simply opens the door to the right help sooner.

The Pinnacle way

This is general information, not a diagnosis — a clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre, under qualified clinician care, never from an app or form alone. Our clinicians may use parent-report tools like the CDI alongside structured observation, then build an individualised plan that can draw on speech therapy where helpful.

Trusted sources

The American Speech-Language-Hearing Association (ASHA) on early communication milestones; CDC and HealthyChildren guidance on language development in infants and toddlers.

Next step — If you would like to understand your toddler's communication clearly, book a developmental review and let our team map their strengths and next steps.