The learning ability:
1º Each timi you study somethhing for first time it will count as 100%
2º If you consume the same item, its % will drop.
3º After studing something, if you study other thing, it will be studied as 100% and letting you at 70%. After that, it doen't matter if you use the same item or if you studie one that you have alredy studied before, it will drop to 50% but count as 70%.
After that, if you again studie something different it will put again at 70% counting as 100%.
Easy example for everyone:
Brain(100%)-Brain(70%)-Singing log(100%)-Brain(70%)-Wood Choppings(100%)-Brain(70%)-Nuts(100%)-Brain(70%)-Brain(50%)-Nuts(35%)-Spinning top(100%)-Brain(70%)-Sinew(100%)-Brain(70%)-Singing Log(50%)-Brain(35%)
Easy to understand i think..