Brown's stages of communication 

The five stages of syntactic and morphological (communication) development are a framework created to help understand and support early language development in the English language. The framework describes the way the number of words/phrases that an individual uses slowly lead to the use of different grammatical structures that increase with difficulty.

Each stage is based on an individual’s mean length of utterance (MLU).

MLU is a widely used measure to look at how long an individual’s sentences are. As an individual’s MLU increases, this is often a sign that the individual is using more complex language.

To find out the MLU we take the number of words and morphemes (small parts of words that have meaning) and divide that by the number of phrases/sentences spoken.

For example: “I go play” (shorter MLU) versus “I am going to go and play with my Lego” (higher MLU).

The five stages of communication can be used as a guide to identify the communication stage of an AAC user. This will help to select words/phrases to use within an AAC system.

Stage One

MLU: 1.0-2.0 (can speak mostly single words and basic two-word phrases)

Age Range: 12 to 26 months

Structure of Words/Phrases: 50-60 basic words/phrases: Milk two| Doggy woof

Stage Two

MLU: 2.0-2.5 (can speak simple sentences and two to three words)

Age range: 27 to 30 months

Structure of Words/Phrases:

• Present progressive: It’s working

• In: In bin

• On: On box

• S plurals: My toys

Stage Three

MLU: 2.5-3.0 (can speak two to four words with more complexity)

Age range: 31 to 34 months

Structure of Words/Phrases:

• Irregular past tense: Me ate fast

• Possessive ending in S: Mummy’s book

• Uncontractible copula: She was sad

Stage Four

MLU: 3.0-3.75 (can speak three to five words with more complexity)

Age range: 35 to 40 months

Structure of Words/Phrases:

• Article: In the rubbish

• Regular past tense verbs ending in ed: I screamed

• Third person regular, present tense: She runs fast

Stage Five

MLU: 3.75-4.5 (can speak four to six words with increased complexity)

Age range: 41 to 46 + months

Structure of Words/Phrases:

• Third person irregular: Daddy gives hugs

• Uncontractible auxiliary: Mummy is smiling

• Contractible copula: They’re tired

• Contractible auxiliary: He’s playing