The notion of the soul was created before modern understanding of neural networks and the physiology of the brain. Decades of experimentation lead cognitive science to consider thought and emotion as physical processes although the experience of consciousness still remains poorly understood. The hard problem of consciousness remains as to whether different people subjectively experience the world in the same way — for example, that the color blue looks the same inside the minds of different people, though this is a philosophical problem with both physical and non-physical explanations.