Although this is a complex question, for the brain is a highly integrated and complex organism, I would like to give you my first response to this question.
The intellect often refers to the ability to process language, to the degree of its development is the degree to understand complex issues. However, an intellectual nature really doesn't consider the ability or capacity to reason or the have good judgement. Aiso, being an intellectual doesn't consider having the ability to properly utilize one's emotions, or Emotional Intelligence. Therefore, those that have the ability to digest books and write reports on them and have the ability to remember what they read many years ago, may not be able to relate to others or make sound decisions. To the degree that the whole of the brain hemispheres are utilized is the degree of true intelligence.I hope this gave you food for thought on your question.