| Term | Definition |
| 0-3 months | head held to one side |
| 0-3 months | able to turn head side to side |
| 3-4 months | holds head in midline |
| 3-4 months | chin is tucked and neck lengthens in back |
| 3-4 months | legs come together |
| 3-4 months | lower back flattens against the floor |
| 4-5 months | head lag is gone when pulled to a sitting position |
| 4-5 months | hands are together in space |
| 5-6 months | lifts head independently |
| 5-6 months | brings feet to mouth |
| 5-6 months | brings hands to feet |
| 5-6 months | able to reach for toy with one or both hands |
| 5-6 months | hands are predominantly open |
| 7-8 months | equilibrium reactions are present |