By this age, babies should be able to smile and coo, look at their parents, react to noises, follow objects with eyes, and push up when on stomach.
By this age babies should be able to roll over, bring objects to their mouth, recognize people, fear strangers, babble, show emotion, and sit without support.
By this age babies should be able to babble, show emotion, sit without support, communicate, crawl and pull to standing.
By this time babies should be able to move things from one hand to another, make sounds, play peek-a-boo, grasp small foods between fingers, and try to repeat words.
12 Months (1 year)
By this age babies should be able to wave good bye, understand simple directions, start to use items correctly, put things in containers and then take them out, walk, and find objects.
18 Months (1.5 years)
At this age babies are only aware of objects that are right in front of them. They may be having temper tantrums, an increase in vocabulary, pretend play, point to body parts.
At this age babies have developed object permanence which means they remember an object exists even if they cant see it anymore. They may begin moving up and down steps, dressing and undressing themselves, and drinking from a cup. They will also start to be more independent.
At this age babies should be more independent, start playing with other kids, defiant, stand on tiptoe, kick a ball, run, speak in short sentences, follow two step directions, and hand dominance.
At this age children should be able to carry out conversations, pedal a bike, catch a bounced ball, hop and stand on one foot, start to work on puzzles, play make believe, and dress/undress themselves.