The Experimenter: 7 to 12 Months

Age (Months): 8

Motor: Uses thumb-finger apposition. Manipulates objects to explore. Pulls up to stand but needs help to get down. Crawls. Drops and throws objects.

Cognition: Recognizes object dimensions. Prefers novel and relatively complex toys. Explores shape, weight, texture, function, and properties (example: in/out).

Socialization: Acts positively toward peers. Is clearly attached to mother. Shouts for attention. Responds to self in mirror. May reject being alone.

Communication: Recognizes some words. Repeats emphasized syllable. Imitates gestures and tonal quality of adult speech; echolalia.

Age (Months): 9

Motor: Stands alone briefly; gets down alone; cruises. Sits unsupported; gets into and out of sitting position alone. Removes and replaces bottle. Puts objects in containers.

Cognition: Uncovers object if observes act of hiding first. Anticipates outcome of events and return of persons.

Socialization: Explores other babies. "Performs" for family ("so big"). Imitates play. Plays action games.

Communication: Produces distinct intonational patterns. Imitates nonspeech sounds. Uses social gestures. Uses jargon. May respond to name and "no". Attends to conversation.

Age (Months): 10

Motor: Holds and drinks from cup. Sits from a standing position. Momentary unsupported stand.

Cognition: Points to body parts. Attains a goal with trial-and-error approach. Searches for hidden objects in a familiar place.

Socialization: Helps dress and feed self. Becomes aware of social approval and disapproval.

Communication: Imitates adult speech if sounds in repertoire. Obeys some commands.

Age (Months): 11

Motor: Stands alone; gets up from all-fours position by pushing up. Climbs up stairs. Feeds self with spoon.

Cognition: Imitates increasingly. Associates properties with objects.

Socialization: Seeks approval. Anticipates mother's goal and tries to change it by protest or "persuasion".

Communication: Imitates inflections, rhythms, facial expressions, etc.

Age (Months): 12

Motor: Stands alone; pushes to stand from squat. Climbs up and down stairs. Uses spoon, cup, and crayon; releases objects willfully. Takes first steps with support.

Cognition: Can reach while looking away. Uses common objects appropriately. Searches in location where an object was last seen.

Socialization: Expresses people preferences. Expresses many different emotions.

Communication: Follows simple motor instructions, if accompanied by a visual cue ("bye-bye"); reacts to "no". Speaks one or more words. Mixes word and jargon.