The heart has its reasons that the mind knows nothing of. I don't know how smart I am. All I know is that everything I have accomplished in my professional career has been through undying tenacity. As a result, some of us have to work harder than others to accomplish the same goal. That statement, however presumes the same level of competence and skill, which is frequently not the case.
Experience plays a pivotal role in the problem solving process.
Philosophers say no. But we sure solve problems faster. Much learning does not teach a man to have intelligence. Heraclitus I cannot do anything about how smart I am, but I can develop my knowledge, skills and experience base. Obviously that makes me more productive and at least appear smarter.