The ancient Chinese conducted crude experiments, separating children from their mothers immediately after birth and bringing them up with animals, or in total seclusion, to see what languages they would talk or how they would describe the world when they grew up. In the abstract, one can imagine experimenting to find out when a child begins to think, and what its first thoughts are, but it is hard to work out what form such experiments might take. A related question is the matter of child prodigies. They are forms of learned behaviour, and the child's prodigious ability must therefore consist in learning the basics, and seeing their potential for development, in a fraction of the time it takes most people. Such questions take us back from science to scholasticism.
Theory is far more abundant than proof.
If the crude analogy with computers holds up, then the synapses of the brain are like the 'gates' on microchips, and we think by sending impulses along preselected paths. One problem with this analogy is that the brain is organic whereas computers are mechanical. There is no way, as yet, to build a computer which is anything but reactive, to make a machine which genuinely 'thinks' on the human model. This seems to move us into the realm of poetry , not science. But it is nevertheless possible that such ideas as chaos theory may provide useful, if mind-boggling, insights into the workings of the brain.