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Three Months Old
Before three months of age, caregivers responses teach infants the signal value of their behaviors allowing infants to learn the stimulus-response sequence. Infants begin to respond vocally to partner at three months of age in the manner of stimulus-response. At three to four months, games and rituals emerge teaching infants the typical patterns that communication follows. -
Eight Months Old
Infants begin gesturing and showing intention in their communication to have their needs answered like gesturing to a bottle to signal wanting food. The intention in their interactions are primarily shown through gestures with their behaviors being meant to influence others. -
One Year Old
Infants have typically spoken their first word by being a year old and use words with or without gestures in place of only gestures. Their first meaningful words expressing intention are spoken at roughly a year or so of age. -
Eighteen Months Old
By the age of eighteen months, toddlers start combining words on the basis of word order rules. They know roughly 50 words. They are capable of learning new word-referents in as few as three exposures. -
Two Years Old
Toddlers begin adding bound morphemes to their speech at two years of age. They have a mean length of utterance (MLU) of 1.6 to 2.2 morphemes and know 150 to 300 words. Their vocabulary growth and word combinations known start to expand rapidly. They know two to four word sentences. -
Three Years Old
At three years of age, toddlers start using more adult-like sentence structure and know roughly 900 words. Their MLU is 3 to 3.3 morphemes. Most utterances have a subject and a verb. -
Four Years Old
Children at four years of age start to change their style of talking to fit their conversational partners. They often substitute individual words into the same sentence frame to create new sentences. Their MLU is 3.6 to 4.7 morphemes, and they know roughly 1,500 words. -
Five Years Old
At five years old, children have 90% of language form and adult syntax learned. -
Six Years Old
Children begin to learn the visual modes of communication like reading and writing at six years of age. They know as many as 2,600 words and understand up to 8,000 root English words and 14,000 derivatives. -
Adolescence
When children hit the stage of adolescence, they are able to participate competently in conversation and the telling of narratives. They know multiple meanings of words and understand figurative language. They use a gender style (genderlect) when speaking. Semantic and pragmatics develop rapidly. In 6th grade, they understand 30,000 words, and they understand 60,000 words as of high school.