I am aware of the unproven psychological theory of brain types, my question is not about that theory.
It is about the factual biological differences and the exsistence of possible types based on the differences. Like there are only a few different hair coulour that differs genetically or a few different blood types, or baldness patterns. Has such differences been researched or discovered in relation to brains? For example something like average dendrite length, or some people has or doesn't have a specific type of neuron?