Via steveberlinjohnson.com (in this edited excerpt Steve Johnson is quoting Antonio Damasio)

On the face of it, idea that the speed of modern life will lead to cognitive overload is a familiar complaint: cultural critics like David Shenk and the late Neil Postman have warned of the dangers of accelerated society. But Damasio has a twist: he’s not saying that the brain can’t keep up with the society — he’s saying that part of the brain can’t keep up with the society, while another part, thus far, has been game to go along for the ride.

“We really have two systems that are totally integrated and work perfectly well with each other, but that are very different in their time constants. One is the emotional system, which is the basic regulatory system that works very slowly, with time scales of a second or more. Than you have the cognitive system, which is much faster, because of the way it’s wired, and because a lot of the fiber systems are totally mylenated — which means it works much faster. So you can do a lot of reasoning, a lot of recognition of objects, remembering names, in just a few hundredths of a second. And in fact it has been suggested that we’re optimizing those times — that we’re working faster and faster…

[however] there is no evidence whatsoever that the emotional system is going to speed up…In fact, I think that it’s pretty clear that the emotional system, because it is a body regulatory system, is going to stay at those same slow time constants. There’s this constant limit, which is that the fibers are unmylenated. So the conduction is very slow.” In a sense, this is an engineering problem: The system that builds somatic markers — the system that encodes the stream of consciousness with value — works more slowly than the system that feeds it data to encode. The result is not a short-circuit of our cognitive machinery. (We can in fact process all that data, and perhaps more.) The danger comes from the emotional system shorting out.