I think that the concept of corralary discharge is very interesting while trying to understand behavior. A few example of different physiological phenomena strike me as appropriate in discussing CD's.

1)While sneezing, your eyes are always closed. Someone once told me, and I have run this experiment several times on my own, that when you sneeze, you can not open your eyes. While this really makes no sense to me, I have tried it, and you can't open your eyes. This doesn't seem to serve much of a purpose, so it makes no sense for us to evolve this silly quirk in our sneezing.

2)In contrast, when we swallow food, we can not intake oxygen at the same time. This would make sense. We have this epiglottis to direct traffic into and out of our respiratory system and our digestive system. I tfollows that we would have evolved this anatomical structure rather than a CD which would prevent the two activities from occurring simultaneously.

Do we develop a CD over time like we evolve an epiclottis? Are CDs some sort of "crossed wires" that have seemingly unrelated functions--seeing and sneezing? Do we evolve needs and not CDs?

Nice thoughts. CD's may also help understand why difficult to pat head and rub tummy at same time? Am not being facetious. Even if we don't have evolutionary story for why particular organizations exist, its nice to be able to infer their existence. Evolve needs or CD's? Are perhaps more or less the same thing, no? PG