Last updated:
April 1, 2026
Summary of important cognitive milestones
| Age | Milestones |
|---|---|
| 1 month old | Reacts to voice, establishes eye contact |
| 2 months old | Tracks object 180 degrees |
| 4 months old | Recognizes hand |
| 6 months old | Grasps, visualizes, and manipulates objects |
| 9 months old | Object permanence, recognizes names, and consonant babbling |
| 1 year old | Say or recognize a few words |
| 16 months old | Follow some commands; indicate wants by pointing |
| 18 months old | Vocabulary of at least 10 words; recognizes “no.” |
| 2 years old | Basic sentence; possessive (”mine”) |
| 2.5 years old | Uses “I” to refer to self; knows name |
| 3 years old | Knows age and sex; mostly understood by strangers |
| 4 years old | Tells a story and uses the past tense |
Piaget’s Cognitive Development Theory
Jean Piaget (1896 – 1980) was a 20th-century Swiss developmental psychologist who came up with cognitive developmental theories
| Stage | Age Range | Description |
|---|---|---|
| Sensorimotor | 0-2 years | A child’s experiences come through the senses. Driven by motor development. Coordination of senses with motor response, sensory curiosity about the world. Language used for demands and cataloguing. Object permanence developed |
| Preoperational | 2-7 years | Acquisition of motor skills. Linguistic skills develop (drive). Symbolic thinking, use of proper syntax and grammar to express full concepts. Imagination and intuition are strong, but complex abstract thought is still difficult. Conservation developed. |
| Concrete operational | 7-11 years | Children begin to think logically about concrete events. Concepts are attached to concrete situations. Time, space, and quantity are understood and can be applied, but not as independent concepts |
| Formal operations | 11+ | Development of abstract reasoning. Theoretical, hypothetical, and counterfactual thinking. Abstract logic and reasoning. Strategy and planning become possible. Concepts learned in one context can be applied to another |
Cognitive Development
Intellectual development begins in early infancy and accelerates more prominently in the second and third years of life. Slow or absent language development may be the first sign of a mental handicap OR other cognitive issues that affect language, such as Autism Spectrum Disorder. It may also indicate a hearing disorder, which should also be ruled out.
- Important aspects of cognitive development
- Learning language – receptive, happens earlier, productive
- Non-verbal communication
- Object permanence – a very important milestone that happens at 9 months)
- Identification of quantity and size (conservation)
- Newborn
- Vision is highly limited at birth (8-12 inches)
- Should react to voice
- Fixes on moving objects
- Prefers human face; establishes eye contact around one month of age (very rewarding to the parent)
- Regains birthweight by 2 weeks; grows 30 g/d until 4 – 5 months of age (at this point birth weight doubles)
- 2 months of age
- Differentiates patterns, colours, and consonants (difficult to notice since the baby cannot speak)
- Able to track an object at midline (180 degrees)
- 4 months of age
- Noticeably more distracted by surroundings
- Explores own body, especially hands and mouth (+ genitals – which is completely normal until about 5 years of age)
- Proprioception matures
- Recognizes emotions in others and mirrors such emotions (social smile, sustained social smile)
- Object permanence not yet developed (surprised by peek-a-boo)
- Growth slows to 20 g/day (birth weight should have doubled)
- 6 months of age
- Primitive reflexes disappear
- More ability to grasp, visualize, manipulate, and explore objects)
- Objects tend to go to the mouth first (Oral fixation; keep small objects and unsafe toys from the baby)
- Baby enjoys dropping objects (lost palmar reflex, perplexed; has not yet developed object permanence, so they think the object has disappeared
- 9 months of age
- Development of object permanence (will uncover the object if hidden)
- Recognize and respond to his/her name
- Language progresses to monosyllabic babbling or consonant voicing (inflection resembles the native language; “mama”, “dada”, “caca”; it is not clear if the infant necessarily knows the meaning or if it is just mimicry
- 12 months of age (1 year old)
- Should recognize words other than “mama” or dada” (monosyllabic babbling)
- Cognitive development is particularly nurtured at this point (as the baby begins to walk and navigate away from the caretaker – encourage and make them safe)
- Follows one-step commands (”Give me”, “Come here”)
- Birth weight should have tripled
- 16 months of age
- Should be able to stack a 2 or 3 block tower – the size which is roughly 3 times the baby’s years
- The child can indicate what he/she wants by pointing (even though vocabulary is limited)
- 18 months of age (1.5 years old)
- Should stack a 4-block tower
- Vocabulary should include at least 10 words and include at least one body part
- A child should have some understanding of the word “no.”
- 24 months of age (2 years old)
- Should stack a 7 block tower
- Should be able to scribble or copy a circle
- Should be able to put a very basic sentence together (”come here”, “want more” – vocabulary expands rapidly after age 2 – words are ideas and concepts – number of words a child can put together in a sentence roughly corresponds to his/her age)
- A child should begin to use pronouns and possessives
- 30 months of age (2.5 years old)
- Should understand the words “I’ and “me” and use them to refer to themselves
- Should respond with name when asked
- Should be able to make horizontal and vertical lines with a crayon
- Birthweight should have quadrupled
- 3 years old
- Should know age and sex (unless there are legitimate gender/sex identity issues)
- Should be mostly understandable by strangers (75% understandable by strangers)
- Should be able to count to 3
- Should recognize at least 3 colors
- 4 years old
- Should be able to draw a square
- Should be able to tell a short story or narrative of something that happened to him/her
- Thought process is usually magical in nature (i.e., monsters under the bed, imaginary friends, playhouse)
- 7 years of age
- Conservation