This is a draft (July 27, 2005) of Chapter III of The Emotion Machine by Marvin Minsky (MIT).
What happens when you stub your toe? You've scarcely felt the impact yet, but you catch your breath and start to sweat—because you know what's coming next: a dreadful ache will tear at your gut and all other goals will be brushed away, replaced by your wish to escape from that pain.
Why does the sensation called pain sometimes lead to what we call suffering? How could such a simple event distort all your other thoughts so much? This chapter proposes a theory of this: if a pain is intense and persistent enough, it will stir up a certain set of resources, and then these, in turn, arouse some more. Then, if this process continues to grow, your mind becomes a victim of the kind of spreading, large-scale "cascade" that overcomes the rest of the mind.
Audio lecture from The Society of Mind course at MIT