For the first few years of life, humans are wonderfully comparable. By the time you have developed the capacity to read this blog, most of your physical development is probably complete. For some early stage of life, a complex organism is busy realizing its physical potential, and ramping up to a full realization of its capacity: for homo sapiens, this lasts years. There are many things at all ages that do not fit onto a linear model like this one, but early on, there are capacities every individual will develop, unless something goes wrong.

The Centers for Disease Control and Prevention (CDC) in the United States are recognized as an authority on categorizing human conditions with regard to disease. They have also published a list of human development milestones for parents to refer to when observing their children’s behavior. These milestones go up to age 5, at which point the child is an adult, and can start tracking the troubling development of their parents. The CDC sorts their developmental milestones into four categories: Social/Emotional, Language/Communication, Cognitive, and Physical Development.

Alternative sources give different presentations of these milestones, but all the sources I have encountered are organized by age of child primarily, and then each of those sections is sorted into domains/categories. I reversed the information hierarchy organizing these milestones: here, they’re presented by domain, with a common age of the child listed under that. I have some other ideas about what to do with these, but I am publishing them here in case anyone else is interested in this sort of presentation. I don’t think this is presented as well as it could be. I can imagine changing this in all sorts of ways, but I’m not going to do it immediately, so I figured I should publish this now. These milestones were originally presented by the CDC as a PDF: this format might be easier for you to manipulate. If you’d rather find something more computer-friendly, you might prefer to look at the source of this post.

Social/Emotional

2 Months

Begins to smile at people

Can briefly calm himself (may bring hands to mouth and suck on hand)

Tries to look at parent

4 Months

Smiles spontaneously, especially at people

Likes to play with people and might cry when playing stops

Copies some movements and facial expressions, like smiling or frowning

6 Months

Knows familiar faces and begins to know if someone is a stranger

Likes to play with others, especially parents

Responds to other people’s emotions and often seems happy

Likes to look at self in a mirror

9 Months

May be afraid of strangers

May be clingy with familiar adults

Has favorite toys

1 Year

Is shy or nervous with strangers

Cries when mom or dad leaves

Has favorite things and people

Shows fear in some situations

Hands you a book when he wants to hear a story

Repeats sounds or actions to get attention

Puts out arm or leg to help with dressing

Plays games such as “peek-a-boo” and “pat-a-cake”

18 Months

Likes to hand things to others as play

May have temper tantrums

May be afraid of strangers

Shows affection to familiar people

Plays simple pretend, such as feeding a doll

May cling to caregivers in new situations

Points to show others something interesting

Explores alone but with parent close by

2 Years

Copies others, especially adults and older children

Gets excited when with other children

Shows more and more independence

Shows defiant behavior (doing what he has been told not to)

Plays mainly beside other children, but is beginning to include other children, such as in chase games

3 Years

Copies adults and friends

Shows affection for friends without prompting

Takes turns in games

Shows concern for a crying friend

Understands the idea of “mine” and “his” or “hers”

Shows a wide range of emotions

Separates easily from mom and dad

May get upset with major changes in routine

Dresses and undresses self

4 Years

Enjoys doing new things

Plays “Mom” and “Dad”

Is more and more creative with make-believe play

Would rather play with other children than by himself

Cooperates with other children

Often can’t tell what’s real and what’s make-believe

Talks about what she likes and what she is interested in

5 Years

Wants to please friends

Wants to be like friends

More likely to agree with rules

Likes to sing, dance, and act

Is aware of gender

Can tell what’s real and what’s make-believe

Shows more independence (for example, may visit a next-door neighbor by himself [adult supervision is still needed])

Is sometimes demanding and sometimes very cooperative

Language/Communication

2 Months

Coos, makes gurgling sounds

Turns head toward sounds

4 Months

Begins to babble

Babbles with expression and copies sounds he hears

Cries in different ways to show hunger, pain, or being tired

6 Months

Responds to sounds by making sounds

Strings vowels together when babbling (“ah,” “eh,” “oh”) and likes taking turns with parent while making sounds

Responds to own name

Makes sounds to show joy and displeasure

Begins to say consonant sounds (jabbering with “m,” “b”)

9 Months

Understands “no”

Makes a lot of different sounds like “mamamama” and “bababababa”

Copies sounds and gestures of others

Uses fingers to point at things

1 Year

Responds to simple spoken requests

Uses simple gestures, like shaking head “no” or waving “bye-bye”

Makes sounds with changes in tone (sounds more like speech)

Says “mama” and “dada” and exclamations like “uh-oh!”

Tries to say words you say

18 Months

Says several single words

Says and shakes head “no”

Points to show someone what he wants

2 Years

Points to things or pictures when they are named

Knows names of familiar people and body parts

Says sentences with 2 to 4 words

Follows simple instructions

Repeats words overheard in conversation

Points to things in a book

3 Years

Follows instructions with 2 or 3 steps

Can name most familiar things

Understands words like “in,” “on,” and “under”

Says first name, age, and sex

Names a friend

Says words like “I,” “me,” “we,” and “you” and some plurals (cars, dogs, cats)

Talks well enough for strangers to understand most of the time

Carries on a conversation using 2 to 3 sentences

4 Years

Knows some basic rules of grammar, such as correctly using “he” and “she”

Sings a song or says a poem from memory such as the “Itsy Bitsy Spider” or the “Wheels on the Bus”

Tells stories

Can say first and last name

5 Years

Speaks very clearly

Tells a simple story using full sentences

Uses future tense; for example, “Grandma will be here.”

Says name and address

Cognitive

2 Months

Pays attention to faces

Begins to follow things with eyes and recognize people at a distance

Begins to act bored (cries, fussy) if activity doesn’t change

4 Months

Lets you know if she is happy or sad

Responds to affection

Reaches for toy with one hand

Uses hands and eyes together, such as seeing a toy and reaching for it

Follows moving things with eyes from side to side

Watches faces closely

Recognizes familiar people and things at a distance

6 Months

Looks around at things nearby

Brings things to mouth

Shows curiosity about things and tries to get things that are out of reach

Begins to pass things from one hand to the other

9 Months

Watches the path of something as it falls

Looks for things he sees you hide

Plays peek-a-boo

Puts things in her mouth

Moves things smoothly from one hand to the other

Picks up things like cereal o’s between thumb and index finger

1 Year

Explores things in different ways, like shaking, banging, throwing

Finds hidden things easily

Looks at the right picture or thing when it’s named

Copies gestures

Starts to use things correctly; for example, drinks from a cup, brushes hair

Bangs two things together

Puts things in a container, takes things out of a container

Lets things go without help

Pokes with index (pointer) finger

Follows simple directions like “pick up the toy”

18 Months

Cognitive (learning, thinking, problem-solving)

Knows what ordinary things are for; for example, telephone, brush, spoon

Points to get the attention of others

Shows interest in a doll or stuffed animal by pretending to feed

Points to one body part

Scribbles on his own

Can follow 1-step verbal commands without any gestures; for example, sits when you say “sit down”

2 Years

Finds things even when hidden under two or three covers

Begins to sort shapes and colors

Completes sentences and rhymes in familiar books

Plays simple make-believe games

Builds towers of 4 or more blocks

Might use one hand more than the other

Follows two-step instructions such as “Pick up your shoes and put them in the closet.”

Names items in a picture book such as a cat, bird, or dog

3 Years

Can work toys with buttons, levers, and moving parts

Plays make-believe with dolls, animals, and people

Does puzzles with 3 or 4 pieces

Understands what “two” means

Copies a circle with pencil or crayon

Turns book pages one at a time

Builds towers of more than 6 blocks

Screws and unscrews jar lids or turns door handle

4 Years

Names some colors and some numbers

Understands the idea of counting

Starts to understand time

Remembers parts of a story

Understands the idea of “same” and “different”

Draws a person with 2 to 4 body parts

Uses scissors

Starts to copy some capital letters

Plays board or card games

Tells you what he thinks is going to happen next in a book

5 Years

Counts 10 or more things

Can draw a person with at least 6 body parts

Can print some letters or numbers

Copies a triangle and other geometric shapes

Knows about things used every day, like money and food

Physical Development

2 Months

Can hold head up and begins to push up when lying on tummy

Makes smoother movements with arms and legs

4 Months

Holds head steady, unsupported

Pushes down on legs when feet are on a hard surface

May be able to roll over from tummy to back

Can hold a toy and shake it and swing at dangling toys

Brings hands to mouth

When lying on stomach, pushes up to elbows

6 Months

Rolls over in both directions (front to back, back to front)

Begins to sit without support

When standing, supports weight on legs and might bounce

Rocks back and forth, sometimes crawling backward before moving forward

9 Months

Stands, holding on

Can get into sitting position

Sits without support

Pulls to stand

Crawls

1 Year

Walks alone

May walk up steps and run

Pulls toys while walking

Can help undress herself

Drinks from a cup

Eats with a spoon

2 Years

Stands on tiptoe

Kicks a ball

Begins to run

Climbs onto and down from furniture without help

Walks up and down stairs holding on

3 Years

Climbs well

Runs easily

Pedals a tricycle (3-wheel bike)

Walks up and down stairs, one foot on each step

4 Years

Hops and stands on one foot up to 2 seconds

Catches a bounced ball most of the time

Pours, cuts with supervision, and mashes own food

5 Years

Stands on one foot for 10 seconds or longer

Hops; may be able to skip

Can do a somersault

Uses a fork and spoon and sometimes a table knife

Can use the toilet on her own

Swings and climbs