An infant cannot create what is referred to as an interactive grin until about two months. He or she can quite possibly need this long for his/her vision and nervous system to grow enough to create a smile in response.
After the first couple of months, infants start to estimate where things are in the room, and they can plan an activity such as grabbing a pacifier. He/she is able to make the rattle create a sound, for an example, which educates him on effect and cause.
In the beginning, your infant will not have the ability to sit-up for long on his/her own. To inspire your infant to sit satisfactory, suspend or place his/her preferred toy before her, then gradually move it from side to side to inspire him/her to reach for the toy and rely entirely on her legs and torso for equilibrium. He/She will be sitting without aid very quickly!