How to process stimuli correctly must be learned. The cortex is split into column of cells. When we are born, the columns overlap and are tangled. As we learn to process stimuli, the cells organise themselves into discrete columns, which no longer overlap. There is a “critical window” for this to happen (usually before puberty, younger for visual processing). If we miss the window, our brains will become “fixed” with tangled columns and won’t be able to process stimuli properly.
Hubel & Wiesel’s experiments prove this.