The Explorer: 12 to 24 Months

Age (Months): 15

Motor: Walks with rapid runlike gait. Walks a few steps backwards and sideways. Dumps toys in container. Takes off shoes and socks. Picks up small objects with index finger and thumb.

Cognition: Imitates small motor acts. Uses toy phone like real one.

Socialization: Likes music and dancing. Pushes toys. Imitates housework. Plays in solitary manner; but likes to act for an audience. Begins make-believe play. Laughs when chased.

Communication: Points to clothes, persons, toys, and animals named. Uses jargon and words in conversation. Has four-to-six word vocabulary.

Age (Months): 18

Motor: Walks up stairs with help; walks smoothly; runs stiffly. Drinks unassisted. Throws ball with whole arm. Throws and catches without falling. Jumps with both feet off floor. Turns pages.

Cognition: Recognizes pictures. Recognizes self in mirror. Remembers places where objects are usually located. Uses a stick as a tool. Imitates adult object use.

Socialization: Explores reactions of others; tests others. Enjoys solitary play. Pretends to feed doll. Responds to scolding and praise. Little or no sense of sharing.

Communication: Begins to use two-word utterances. Has approximately twenty-word vocabulary. Identifies some body parts. Refers to self by name. "Sings" and hums. Plays question-answer with adults.

Age (Months): 21

Motor: Walks up and down stairs with help of railing or hand. Jumps, runs, throws, climbs; kicks large ball; squats to play; running is stiff. Fits puzzle together. Responds rhythmically to music with whole body.

Cognition: Knows shapes. Sits alone for short periods with book. Notices little objects and small sounds. Matching objects with owners. Recalls absent objects or persons.

Socialization: Hugs spontaneously. Plays near but not with other kids. Likes toy telephone, doll, and truck for play. Enjoys outings. Becomes clinging around strangers.

Communication: Likes rhyming games. Pulls person to show something. Tries to "tell" experiences. Understands some personal pronouns. Uses I and mine.

Age (Months): 24

Motor: Walks watching feet. Runs rhythmically but unable to start or stop smoothly. Walks up and down stairs alone without alternating feet. Pushes tricycle. Eats with fork. Transitions smoothly from walk to run.

Cognition: Matches familiar objects. Comprehends one and many.

Socialization: Can role-play in limited manner. Engages in pretend lay constrained by the objects. Enjoys parallel play predominantly. Prefers action toys. Cooperates with adults in simple household tasks. Communicates feelings, desires, and interests.

Communication: Has 200-300-word expressive vocabulary. Uses short, incomplete sentences.