The nervous system is sensitive to changesit is designed to detect edges and differences between light and dark areas in objects, disregarding changes in light intensity. This suggests the viewpoint that change is more important than the periods of similar conditions between them.
What we see depends greatly on what exists around the object we are looking at. It is the comparative difference in light intensities between surfaces, rather than the absolute light intensity on each separately, that is of prime interest to the nervous system. While we dont seem to notice things while they stay constant, change gets our attention. This supports the idea that, in general, it is the changes we notice and not the stable conditions that exist between these periods of change. For example, when we cut our hair we can feel the change in its weight, even if the difference in hair length is very small. Could this be the work of those corollary discharge signals reporting to a center in our brain that our hair is still 3 feet long, only to meet with contradictory sensory input signals reporting our hair is actually three inches shorter? Over time we become used to these changes, and our hair doesnt feel so noticeably short anymore.
These general principles of sight and of sensory perception can be applied to our larger sphere of behavior. We dont notice the shoes we are wearing until they start to hurt. We dont notice our the weight of our hair until we get a haircut. And in a broader sense, we dont notice the importance of a relationship until it is altered, or gone. We dont notice how cold and dark Winter was until Spring comes with warm breezes and long, bright days (were still waiting). We dont seem to notice things until they are altered or missing. This view of the nervous system, therefore, gives us insight into our own behavior on a larger and more complex scale.
Interesting and appropriate extension. I'm not sure I'd call it corollary discharge, but we certainly have internal models of reality (to which CD's contribute) and tend to pay attention to sensory input more when it is inconsistent with those models (something has "changed") than when it is consistent with them. PG