| Age (months) | Motor | Visual/Problem Solving | Language | Social | 
| 1 | slight head raise | visually fixes | alert to sound | regards face | 
| 2 | holds up head | visually follows past midline | social smile | recognizes parent | 
| 3 | holds head steady | responds to visual threat | coos | reaches fo objects | 
| 4 | rolls front to back | reaches with arms in unison | laughs, orients to voice | looks around environment | 
| 5 | sits supported | transfers objects | "ah-goo" |  | 
| 6 | sits unsupported | unilateral reach | babbles | recognizes strangers | 
| 7 | creeps | inspects objects | orients to bell | finger-feeds | 
| 8 | crawls | inspects objects | Mama/dada |  | 
| 9 | pulls to stand | pincer grasp, holds bottle | Mama/dada descriminately | explores environment | 
| 12 | walks alone | mature pincer grasp | 2 additional words | comes when called | 
| 15 | creeps up stairs | scribbles, 2-block tower | 4-6 words | uses spoon independently | 
| 18 | runs, throws from standing | 3-block tower | 2 word combinations | plays with other children | 
| 21 | squats, walks up stairs | 5-block tower | 50 words | asks for food/toilet | 
| 24 | walks up & down steps | removes shoes, pants, etc | pronouns | parallel play |