VERY interesting study! It is about human appetites (apparently, we have five evolutionary ones) and, although it covers animals diets, it's wild animals (VERY different from pet parrots) but it does teach about how this 'finely tuned mechanism' can be turned askew by processed food (which, in my mind, it's the pellets and the human food of the bird world).
https://www.mnn.com/food/healthy-eating ... a-40378997




