Yeah about 3 for us.
She’s 4 now and quite clever with it, there’s this move she doesn’t want to do in Gymnastics (there’s a whole other thread I could go into about Gymnastics!) My Wife promised her a toy if she did it, and despite every fibre of her being telling her not to do it, she did and got the toy. The following week she did it again and was rewarded (like a dog) with a treat, she wanted another toy, but she got some chocolate, this went on for weeks.
Now the Gym is massive, she they train right down the other end. Wife had seen her do it the first time, but not since. When she was chatting to the coach she asked how she was getting on with it “oh, she did it once, but she simply refuses to do it again”.
I have to admit, I was impressed.