Birth to 3 months

• Reacts to loud sounds with startle reflex

• Is soothed and quieted by soft sounds

• Turns head to you when you speak

• Wakes up when there are loud voices and sounds

• Smiles in response to certain voices when spoken to

• Seems to know your voice and quiets down if crying

4 to 6 months

• Looks or turns toward a new sound

• Responds to "no" and changes in tone of voice

• Imitates his or her own voice

• Enjoys rattles and other toys that make sounds

• Begins to repeat sounds (such as "ooh," "aah," and "ba-ba")

• Gets scared by a loud voice or noise

7 to 12 months

• Responds to his or her own name, phone ringing, or someone's voice, even when not loud

• Knows words for common things (such as "cup" or "shoe") and sayings (such as, "bye-bye")

• Makes babbling sounds, even when alone

• Starts to respond to requests (such as "come here")

• Looks at things or pictures when someone talks about them

• Enjoys games such as peek-a-boo and pat-a-cake

• Imitates simple words and sounds; may use a few single words meaningfully

1 to 2 years

• Follows 1-step commands when shown by a gesture

• Uses words he or she has learned often

• Uses 2-to-3-word sentences to talk about and ask for things

• Says more words as each month passes

• Points to some body parts when asked

• Understands simple "yes-no" questions (such as "Are you hungry?")

• Understands simple phrases (such as "in the cup" or "on the table")

• Enjoys being read to

• Understands "not now" and "no more"

• Chooses things by size (such as big or little)

• Follows 2-step commands (such as "Get your shoes and come here")

• Understands many action words (such as run or jump)