MacArthur–Bates Communicative Development Inventories (CDI)

A simple checklist a parent fills in — turning what you already notice about your child's words and gestures into a clear picture of early communication.

In short

The MacArthur–Bates Communicative Development Inventories (CDI) are a well-established set of parent-report questionnaires that measure a young child's early language and communication. Because you, the parent, complete them based on what your child does in everyday life, the CDI captures real-world communication rather than how a child behaves in an unfamiliar room. They are widely used from around 8 months to 3 years to track words a child understands, words they say, gestures, and the first steps of sentence-building.

What the CDI assesses

The CDI comes in forms suited to different ages, and together they look at several threads of early communication:

• Words understood (receptive vocabulary) — the words your child seems to recognise, even before they can say them.
• Words said (expressive vocabulary) — the words your child actually uses.
• Gestures and actions — pointing, waving, showing, and play gestures that are the foundation of communication before speech.
• Early grammar — for older toddlers, how words begin to combine into short phrases and sentences.

Because parents see their child across many natural moments — meals, play, bath time — the CDI is considered a reliable, low-stress way to gather rich information. It is a screening and research-supported tool, not a stand-alone diagnosis. A score below the typical range is best understood as an invitation to look more closely with a professional, not a verdict.

When it helps

The CDI is especially useful when a parent or clinician wants to understand a late talker, track progress over time, or add a parent's everyday observations to a fuller developmental review. It works alongside — never instead of — a clinician's direct assessment of how a child listens, plays and communicates.

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 a single form. Our team may use parent-report tools like the CDI together with structured observation, then shape an individualised plan that can draw on speech therapy where it helps your child flourish.

Trusted sources

ASHA guidance on early language development and parent-report measures; CDC developmental milestone resources on communication; the WHO Nurturing Care Framework on early childhood communication and learning.

Next step — If you'd like to understand your child's early words and gestures, book a developmental review where a clinician can combine your everyday observations with a careful look at how your child communicates.