My god daughter is about 3.5 years old. She has demonstrated she is aware of when she needs to pee/poop and if naked will ask for a pullup to be put on just so she can use it. I believe if she wanted to she could consistently use the potty.
However, she seems strongly opposed to using it. As I said she will ask for a pullup so she can use it rather than use the potty, even if she is encouraged to use the potty. Likewise if we tell her we see signs she needs to use the potty and ask her if she wants to sit on it she will refuse to. She will claim to not be pooping when she is so she can keep pooping in her pullup instead of sitting on the potty.
She doesn't seem afraid of the potty, she has to sit on it to get a pullup (rather or not she uses it) and often will without any obvious fear. She just prefers not to. If anything she seems more willing to cooperate and sit on the potty when she knows she doesn't need to go then when she actually needs to use it.
She is a very strong willed child, and has been known to insist on things just to be contrary at times, but usually only when she is angry or tired. I could believe that at times she may resist using the potty just because she knows she is wanted to, but the consistency with which she resists, even when otherwise happy and in a cooperative mood, is odd. There are a few times when she does request to use the potty on her own, but they are definitely the exception.
We make a big deal of encouraging her when she does us the potty, singing and dancing and telling every member of the family how good she did using it. She clearly seems to enjoy this with happy grin and wanting to tell those who weren't there. It seems like she enjoys the results of using the potty afterwards.
What can we do to make her want to use the potty, or at least to try to remove whatever is motivating her to actively avoid using it?