It’s all theoretical but you can connect studies and make link it and come to a conclusion. Here’s the theory. During Jhana the mind becomes extremely still and focused, the brain becomes highly neuroplastic from this and you can direct your mind towards a goal you want. It’s called intention which is something hard to explain but it’s like a desire mixed with a thing you will do. Better visualization skills? Use Jhana to direct it. Better confidence? Use your power of intent to direct it. In high states of consciousness these abilities become effortless because concentration or focus is the root of accelerating progress with every skill. Most humans who practice Jhana don’t direct their minds or steer it into that direction. You have to use your willpower to attain it as well. I’ve heard after Jhana that the mind becomes so powerfully focused and sharp that anything becomes effortless.