From time to time I encounter people who claim that our brains are really slow compared to even an average laptop computer and can't process big numbers.

At the risk of revealing my complete lack of knowledge of neural networks and how the brain works, I want to ask if this is actually true?

It took massive amounts of number crunching to create movies like James Cameron's Avatar. Yet I am able to create more realistic and genuine worlds in front of my minds eye, on the fly. I can even simulate other agents. For example, I can easily simulate sexual intercourse between me and another human. Which includes tactile and olfactory information.

I am further able to run real-time egocentric world-simulations to extrapolate and predict the behavior of physical systems and other agents. You can do that too. Having a discussion or playing football are two examples.

Yet any computer can outperform me at simple calculations.

But it seems to me, maybe naively so, that most of my human abilities involve massive amounts of number crunching that no desktop computer could do.

So what's the difference? Can someone point me to some digestible material that I can read up on to dissolve possible confusions I have with respect to my question?