For what it's worth, the actual structure of the brain starts off with way too many neurons and connections and starts paring them down. Learning is creation, b

For what it's worth, the actual structure of the brain starts off with way too many neurons and connections and starts paring them down. Learning is creation, but it is also destruction. Removing useless connections is valuable. A lot of the paring down happens in your teens with the process reaching a stable state in the mid-20s. This doesn't mean learning ceases past the point (clearly not). But it does mean that changing synaptic weights and forming new synapses comprise the bulk of learning rather than new neuronal projections and creating new neurons of which the later two become insignificant with small exceptions (such as the generation of new neurons in a small region called the SVZ and also in the hippocampus, a region important for memory though I don't know if the role of these new neurons is known in any great detail). Adult learning necessarily uses restricted mechanisms compared with children and adolescents. It's still a general learning machine though, though rate of learning might suffer (I'm not familiar with that part of the field).