Babies are now usually bouncy and happy.  They like to stand with support (it will not make them bow legged), and they smile for nearly everyone.

They can track you with their eyes as well as by turning their heads.  Someone may open a door and the child can track that person all around the room.

If they sit with you while you have meals, they will start watching your forks, glasses, etc.  Some will open their mouths when you place food in yours.  They are really paying attention and are figuring this out.

Some will begin to roll in one direction at 4 months of age.  Time to be careful.  In my practice, several babies a year will fall off beds, countertops, changing tables, etc. Although falls can be dangerous, most of these falls do not end up with significant injuries…just rattled parents.

Stranger anxiety normally has not surfaced at this time.  You can usually pass your child around the dinner table and they are happy with whoever holds them.  An occasional baby, however, will begin to exhibit fear of strangers at 4 months.