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Timeline Project


Speech and Language


Cognition and Perception

While not social in nature, unoccupied play is an important precursor to more social play. The infant is primarily occupied with their internal state, and this play continues until around 3 months.

The sounds that infants make beginning at birth are called reflexive vocalizations. These sounds include crying, burping, sneezing, and coughing. This is part of the prelinguistic period of phonological development. Quasi-resonant nuclei are sounds with limited resonance but a vowel-like quality.

At birth, infants are able to recognize their mother's face, and discriminate their mother's voice from others. This marks the beginning of the sensorimotor period, which continues until approximately 2 years of age. Interestingly, infants are able to detect every phoneme contrast in human language! 


Beginning around 1 month, the infant will begin engaging in sensorimotor play. This will continue until around 12 months.  Mutual gaze develops around 4-6 weeks. 

1 month

At two months, the infant will search for its mother's voice, and a social smile appears around 6 to 8 weeks. They will begin responding to joint attention

The infant is beginning to hold their neck steady, and will lift their head during tummy time around 2 to 3 months! This is also when the stepping or dancing reflex disappears. 

Around 2 to 3  months, gooing and cooing noises begin to appear. 

The infant is beginning to selectively attend to the external environment!

2 months

Between 3 and 4 months, rituals and game playing emerge. This marks the beginning of solitary play, which the child will engage in until around 2 years. 

The infant will grasp a rattle when it is placed in their hands. Another reflex present at birth disappears in this 3 month stage: the phasic bite reflex.  

3 months

The infant begins to positively respond to smiles between 4 and 6 months. 

The infant will begin to roll over around 4 to 5 months. Another two reflexes make their exit: the rooting and sucking reflex, and the startle/moroe reflex. The former typically fully disappears by 4 months, the latter by 5 months.

Vocal play emerges between 4 and 6 months, and the infant begins to form fully resonant nuclei during this same time frame. Additionally, a dramatic increase in vocal and non-vocal imitation is evident between 4 and 8 months. 

4 months

The infant begins to reach for and grab objects. The palmer grasp reflex disappears between 5 and 6 months. Additionally, at 5 months, the infant begins to mouth objects. 

At 5 months, the infant can discriminate their own language from others. 

The infant begins to recognize and respond to their own name, and begins to perceive their own face between 5 and 8 months.


The child understand and produces all types of embedded clauses between 12 and 13 years. 

The formal operations stage begins begins between 12 and 15 years of age. 

5 months
6 months

The infant transfers an object from hand to hand around 6 months.  The tongue thrust and bobinski reflexes can begin to disappear around 6 months, but both can take until 2 years of age to fully disappear. 

The infant will begin to find objects that they have hidden between 6 and 8 months. Additionally, the infant can attempt to retrieve a partially hidden object at 6 months. 

7 months

The infant will shake and bang toys at 7 months. 

Reduplicated babbling emerges between 7 and 10 months. 

8 months

The infant will begin to imitate waving bye-bye between 8 and 10 months. Between 8 and 12 months, the infant will begin to use intonation to convey requests, frustration, greetings, or pleasant surprise. Additionally, gestural and communicative intention develops

The infant begins to crawl around 8 months. 

At 8 months, the infant begins to understand common phrases. 

Now, the infant's perceptual ability is restricted to their native language. This happens between 8 and 10 months. 

9 months

At 9 months, the infant will begin to initiate joint attention. They can follow parental pointing and glancing, and will shake their head "no." Ritualized requests will begin between 9 and 13 months. 

Pincer-grip ability forms. 

10 months

In gestural development, the infant will begin to reach and raise their arms. Between 10 and 12 months, deictic gestures will begin to appear. 

The infant will pull to stand around 10 months. 

The infant begins to recognize familiar words. This is an incredible cognitive achievement, because the child's brain has begun to find ways to break up the adult speech stream. 

11 months

The infant begins to wave hi or bye around 11 months. 

Between 11 and 14 months, variegated babbling emerges. 

12 months

At 12 months, functional gestures begin to appear. Iconic gestures appear between 12 and 15 months. Additionally, we begin to see pragmatic functions between 12 and 18 months, including: naming/labelling, requesting actions, exclaiming, protesting/rejecting, calling, and routine. During this 12 to 18 month range, we also see functional/relational play emerge.

At one year, the child begins stacking blocks on top of one another. 

The child begins to produce their first words! This typically emerges between 12 and 15 months. Between 12 and 18 months, the child will begin to use the negative "no" at the single word level.  There is no tense or aspect marking during this 12 to 18 month range. Receptive language continues to develop; now the child prefers the correct word order in speech.  In questions, or interrogatives, the child will rely on intonation or interrogative words alone between 12 and 22 months. 

The child can find a hidden object; this is an important milestone in object permanence.

13 months

At 13 months, the child will begin to clap their hands. 

14 months

At 14 months, the infant continues to understand more words than they can say, but their spoken vocabulary has expanded to approximately three to five words. 

15 months

Symbolic gestures begin to emerge around 15 to 16 months. 

At 15 months, the child will begin to walk independently.

16 months

The child's receptive vocabulary has grown to include around 90 to 320 words.

17 months

At 17 months, the child is able to use word order to interpret sentences.

18 months

Pragmatic functions, such as repeating/practicing, verbal accompaniments to action, direct requesting and demanding, content questioning, statements, declarations, and comments develop between 18 and 24 months. After 18 months, the child begins to engage in symbolic/pretend play.

The child begins to produce two-word utterances between 18 to 20 months; they have approximately 50 words in their productive vocabulary. 18 months marks the beginning of the vocabulary spurt as well. Negatives use "no" to negate, but still omit the subject. This continues from 18 to 27 months. 

The child can begin finding objects hidden by others, and learn to use objects to influence their world.  At 18 months, object permanence and mean-ends behavior has been fully achieved.

19 months

The child masters the present progressive -ing between 19 and 28 months, but without the auxiliary verb. 

20 months
21 months
22 months

The child will begin using interrogatives that include:

"That x?"

"what + noun phrase + (doing)?"


"Where + noun phrase + (going)?"

23 months
24 months

At two years, the child will begin to engage in spectator/onlooker play, and parallel play will emerge at 2 and a half years.  The child begins to use centering narratives to tell others about familiar sequences and events, and between 2 and 3 years they will begin using centering narratives about self-generated, fictional events. 

At 24 months, the child will begin to use writing utensils to draw.

The child starts to use negatives in uncontracted forms between 30 to 36 months. Locational prepositions (in, on, and to) appear at two years. Between 28 to 30 months, the child will begin to use "no" to negate, but now with the subject.  Auxiliary verbs emerge around 30 months, including: can't, don't, won't, do, have, can, be, and will.  The child's average MLU is around 2. They will begin to use the possessive -'s between 26 and 40 months.  The regular third person -s emerges between 26 and 46 months; while the regular past -ed emerges between 26 to 48 months.  The child continues to use interrogatives, but now with the verb phrase/predicate, and this skill emerges between 28 and 30 months. Additionally, the interrogatives include some auxiliary verbs and add the copula (33 to 37 months). Lastly, a stage known as pre-reading, emergent literacy, or early literacy begins between 2 and 6 years. 

The preoperational stage begins between 2 and 7 years of age, and categorization is fully achieved between 2 and 3 years. 

3 years

At 3 years, the child will use modal auxiliary verbs in indirect requests. They will ask yes or now questions, include verbal accompaniment, contingent inquiry. They will request permission around 3 years and 9 months, and will use cohesion devices in discourse between 3 and 4 years. Between 3 and 4 years, the child will begin to engage in associate play.  The child's narrative development continues, and now they will begin temporally chaining narratives with familiar activities.  In preschool, this development will include the descriptive sequence narrative (stage 1), the action sequence narrative (stage 2), and the reaction sequence narrative. 

Between 38 and 40 months, negatives will use contracted forms. The child's MLU is around 3.0, and noun phrase elaboration is evident, including the determiner, adjective, and some post-noun modifiers. The child will reference time in past, present, and future events between 3 and 3.5 years. They will then flexibly describe past, present, and future events between 3 and a half and 5 years.  The child will use the irregular past tense at 46 months. Auxiliary verbs that emerge at 40-42 months include: could, would, should, must, and might.  Locational prepositions emerge as well, including "under," and "next to".

The child begins understanding their own mental and emotional states at 3 years. 

4 years

At 4 years, the child will begin to use suggestion. This will develop into physical justification at 4 years and 6 months, and indirect requests at 4 years and 9 months. Code switching is a skill that emerges at this time in communication with others, and at 4.75 years the child will understand and respond to indirect requests. Cooperative/social play emerges. 

The child's MLU is now around 4.0. They will use negatives and rearrange with an auxiliary between 4 and 5 years. Noun phrase elaboration includes quantifiers, demonstratives, and post-noun prepositional phrases.  The auxiliary "to be" and copula are mastered, however, the copula tends to take a little longer. Indirect objects are added to declarative sentences.  Locational prepositions now include behind, in back of, and in front of. 

Theory of mind develops between 4 and 5 years of age. 

5 years

The child will use justification in directives and requests, and may discuss as many as 50 different topics within 15 minutes.  Causal chaining narratives emerge. 

The child understands figurative language related to physical characteristics between 5 and 7 years, and begins to understand passive sentences around 5 and a half. 

6 years

The child introduces and maintains an abstract topic. Abbreviated episode narratives emerge. 

The child bgins to decode words in stage 1 of literacy development. 


The child is able to introduce and maintain a concrete topic between 7 and 8 years. The complete episode narrative begins within this 7 to 8 range, as well. 

Reversible passive sentences are produced; this emerges between 7 and a half and 8 years. 

The concrete operational stage begins around age 7, this stage will continue until age 11. 

7 years

The child achieves autamaticity in their reading between 8 and 10 years. 

8 years

Between 9 and 10 years, the child understands figurative language related to psychological characteristics, including "feeling blue".  The child begins to produce agentive nonreversible passive sentences.

9 years

The child begins reading to learn between 10 and 14 years. 

10 years
11 years

Complex episode narratives emerge around 11 years, and interactive episode narratives emerge beyond 11 to 12 years. 

At 11, adult-like definitions for familiar words emerge.  The child will produce instrumental nonreversible passive sentences between 11 and 13 years. 

12 years
13 years

The child will begin reading for ideas between 14 and 18 years of age.

14 years

Critical reading emerges around 18 years, and the young adult will begin to define abstract words. 

15+ years

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