I was a very intelligent child. In fact, I was a very strong willed child that didn't accept any reason for anything at face value. If it made sense to me, I did it. If it didn't make sense to me, I'd argue about it. Intelligence and retention are more linked.
Some dogs learn quickly and forget just as quickly.
Goldens are like that. They have to be worked frequently in order to stay sharp. Other dogs learn quickly and never forget. Airedales are like that. She is too smart to be worked every day.