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3 Months
When an infant reaches 3 months of age they begin vocally responding to partners, caregivers, and the babbling stage is very active. This is the first measurable sign of communication. -
8 Months
At 8 months of age, babies begin using gestures to aid communication. This allows for more communication to occur between the child and caregivers, and more expressions and intentions to form in communication. -
12 Months
At one year old babies begin to speak, and fill intentions previously signaled by gestures with words. This is progress from the babbling stage to simple word or two word utterances. -
18 Months
At a year and a half children begin to order their words on the basis of word-order rules. These rules are usually established by their caregivers and are reflective of sociolinguistic factors the child is exposed to. -
2 Years
By their second birthday children begin adding bound morphemes such as -s, -ing, and -ed. The average length or mean length of utterances (MLU) is 1.6-2.2 morphemes. This allows for discussion of time and space, and introduce children into marking past and future tense verbs. -
3 Years
At 3 years old communication starts to resemble more adult like sentence structure, and the MLU increases to 3.0-3.3 morphemes. At this point, language is highly dependent on exposure and social influence. -
4 Years
Four year old children begin customizing their communication style according to their partners, and MLU continues to grow. Average MLU range for 4 year old is 3.6-4.7 morphemes. Observation methods at this stage can highlight the difference between home and school settings on linguistic performance. -
5 Years
By the time children reach 5 years old over 90% of language form is established. Isolation or lack of social exposure can demonstrate significant deficiencies by this age. -
6 Years
By 6 years old children begin to learn the visual components of communication such as writing and reading. Literacy in different modalities of communication can showcase further deficiencies or work in tandem to increase competency in the child. -
Adolescence
By the time adulthood is reached children are able to competently communicate in conversation, tell narratives, has multiple established meanings for words, understands figurative language, and also employ a gender style when talking. Linguistic competency has been established by this age although refinement continues on through later life.