Besides the "eye multitasking", where the eyes sometimes have to focus on three monitors at the same time and on a colour pattern in parallel, the understanding of light and all the associated effects probably play the biggest role. As an image editor, you juggle with numerous controls and tools to achieve a result that, on the one hand, is correct in terms of colour, brightness, perspective and the message to be conveyed, and on the other hand, is "human", i.e. allows for imperfections and blemishes and thus appears pleasant to the viewer. So a certain level of empathy certainly plays a big role as well, because you have to think in all worlds - the perfect one, the human one, the client's one, the end client's one, etc. - while working.