Counting and adding

Last night, on my car ride home, I was listening to a program that spoke about numbers and mentioned that around age 3.5 children start being able to understand integers.

As an experiment, I started asking PJ simple addition and subtraction questions at dinner. He easily did the add one or two, had trouble adding larger numbers and refused to do any subtraction problems. (I think some of that started when I asked him is he had jelly beans and I took some away... At least I was able to appease him with raisins for dessert instead of the requested jelly beans.)