My 2 peach faced lovebirds (I lost my sweetest one a while back) really do evolve. They are about 8 years old now (will live for 15-20 years), a girl and a boy, brother and sister. They live, when I am not around, in separate cages. When I am around I take them out and let them fly around the big hallway they live in and play on a birdie playground and perches. Plus I let them climb all over me.
The girl bird was always a pretty dangerous biter.
Who knows why, but in the past month or so, she completely gave up biting! Now she snuggles and kisses and gently nibbles me.
She must have had an epiphany of some sort, all on her own.