From Birth to Third Year (From Preyer, Paton, Church and Peterson, and others)
The study of the early years of infancy resulted long ago in the formulation of outlines showing the normal course of development of the child. The following composite of several such outlines represents the simplest and earliest type of age scale for the measurement of psychophysical status:
1st Week - Sensitive to light, reaction to touch, evidences of audition, sensibility to taste.
2d Week - Notices candle, facial reaction suggesting pleasure.
3d Week - Sheds tears.
4th Week - Smiles and makes vowel sounds.
1st Month - Taste, smell, touch, sight, hearing active. Sleeps two hours at a time, sixteen hours out of twenty-four.
2d Month - Occasional strabismus, recognizes human voice, turns head toward sound, pleased with music and with human faces, laughs at tickling, clasps with four fingers by end of second month, makes first consonants.
3d Month - Cries with joy at sight of mother or father. Eyelids not completely raised when child looks up. Knows sound of watch. Listens with attention.
4th Month - Eye movements perfect. Sees objects move toward eye. Pleased at seeing self in mirror. Opposes thumb to fingers. Head held up permanently. Sits up with support at back. Begins to imitate.
5th Month - Discriminates strangers. Enjoys crumpling and tearing paper, pulling hair, ringing bell. Sleeps ten hours without food. Makes consonants L and K. Seizes and carries objects to mouth.
6th and 7th Months - Raises self to sitting posture. Laughs. Raises and drops arms when pleasure is great. Teeth begin to appear. Astonishment shown by open mouth and eyes. Turns head as sign of refusal.
8th and 9th Month - Stands on feet without support. Claps hands for joy. Afraid of dogs. Turns over when laid face down. Turns head to light when asked where it is. Voice is more modulated. Questions understood before child can speak.
10th to 12th Months - First attempts at walking. Sitting has become a habit. Stands without support. Whispering begins. Pushes chair. Obeys command "Give me your hand."
13th to 15th Months - Says "Papa" and "Mamma" Raises itself by chair. Imitates coughing and swinging of arms. Walks without support. Understands about ten words.
16th to 19th Months - Sleeps ten hours at a time. Associates words with objects. Blows horn, strikes with hand or foot, waters flowers, tries to wash hands, to comb and brush hair, and to execute other imitative movements.
20th to 24th Months - Makes marks with pencil on paper. Executes simple orders with surprising accuracy.
25th to 30th Months - Distinguishes colors, makes sentences of several words, begins to climb and jump and to ask questions.
30th to 40th Months - Goes up stairs without help. Clauses formed. Words distinctly spoken. Influence of dialect appears. Much questioning.
Beyond 40th Month - See standard Intelligence Scales and specific Performance Tests.