In most ways, the toddler stage for your twins is the same as singletons. Meeting each developmental milestone depends on their brain cells interacting with each other. Important factors that influence your twin dynamos are their experiences and interactions with their environment, which includes you (one more thing you'll be blamed for when they get older). However similar in development to single birth children, there are some unique characteristics seen mainly in twins.
Speech and Language
Speech in toddlers normally starts by 18 months with about a 10-word vocabulary. Normally, by the age of 2 years, toddlers have two- or three-word phrases with about 50 understandable words at their command. By 3 years, that expands to around 450 words (so much for peace and quiet). An interesting twist, however, (always something) is that twins, particularly identical twins, may be slower in speech development. They may also develop their own language know as "twin speak" or "twin language." Because twins tend to be born premature, they may also stutter. In most cases, all of these peculiarities dissipate naturally. If you are worried, see your pediatrician.
Identical or maternal twins normally develop socially at about the same speed. Fraternal or non-identical twins may develop slower or faster than the other, much like single birth children. However, twins -- maternal and fraternal -- tend to be close and depend on each other for support. This might play a role in shyness and a reluctance to socialize. As they grow older, each twin’s individualism shines through. On the plus side, twins normally learn how to share earlier than single birth kids.
Learning to walk spells double trouble. It’s usually hard enough to keep an eye on one, but two! (You should be elevated to sainthood.) By 18 months your terrible twos are walking and climbing stairs. They drink from a cup, feed themselves (and each other) with a spoon and become quite the little dresser-uppers. Around 2 years or so, they master the art of ball throwing (indoors and out), drawing circles on paper -- or walls-- and are able to give you a “run” for your money -- literally. (Let’s not mention tricycles at 3 years!)
Most identical twins show very little difference in intelligence. According to Caroline Bowen, a speech-language pathologist, the stretch in IQ between your two little geniuses is probably no more than five points. Fraternal twins may vary more, as singleton siblings vary from each other. Identical twins grow at about the same pace cognitively, provided there are no mental or physical problems. All twins have their own little world which only the two of them understand -- make believe friends, secrets and places -- that you are not privy to. They learn to twist off jar lids, do simple puzzles and open doors (now you’re really in trouble).