personally i think it depends on their personality (as well as the environment they grow up in)...

dd is 15 months and can probably say about 100 words, has been talking ALOT since about 13 months... but from the age of about 6 months we taught her all the objects in the room (of course she couldn't say them, but from 7 months could point them out), and this gradually became broader and broader, to her being able to point out just about any object she had ever seen once or twice before.... she has been pretty 'thirsty' for knowledge from the time we started teaching her the name of objects... on the other hand, she is not a very 'brave' girl, as in she is quite tame and timid when it comes to riding on her little car, and riding on see saws etc at playgroup like the other kids do.... she loves being outside, but probably her favorite thing is reading a book, where she points at each picture in the book and says what it is.

maybe your little one will be more advanced in other areas, they all have their little quirks, i wouldn't worry