Computing composite functions This may not be strictly a computer science question but is related.

Whenever there is some function that computes more than two elements, is it possible that all elements are computed at once? Or is computing in composite/series a required limitation of the brain?

For instance, to add three numbers, we add two and then and the third to the result of the first addition. Is it possible for the brain to take all three numbers and process them at once with no intermediate step? Is it possible for machines? Is it possible with quantum computing?

In the case of the brain's inability to make this computation, is it because we are trained to compute in a certain way or is it an inherent limitation?
Definitely possible for a computer, since three-input logic gates exist.   Possible for humans too, at least as far as conscious operations are concerned.  If you show me a partition of 13 into no more than 4 parts (e.g. 5+3+4+1), I can recognize it without any intermediate calculation simply from long experience playing bridge.