Definition: Humphrey - Ipsundrum

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An IPSUNDRUM is a coinage by Nicholas Humphrey to designate his perception of the specific means by which the brain records sense data. Combined with his notion of Sentition these are some of the most powerful ideas in regard to conceptualization of the interaction of mind and brain in more than two thousand years of continuous and largely valueless discourse.


Humphrey declares that the brain has no direct way of recording what a sense event is, but it can and does record its own responses to patterns of sense input. But since it itself creates these responses it can recreate them. By binding its response to another pattern it can create arbitrarily it can then reference the sense pattern in regard to other things.

To quote his paper The Invention of Consciousness:

It begins, as I see it, with the creatures that were our far distant ancestors, floating in the seas, making evaluative responses to stimuli at the body surface: “wriggles of acceptance or rejection”. These responses, to which I’ve given the general name “sentition”, have been honed by natural selection, so as to be well adapted to the creature’s needs—taking account of what kind of stimulus is reaching the body surface, what part of the body is affected, and what import this has for biological well-being. From the start then, the responses can be said to be meaningful—which is to say they potentially carry a lot of information about what the stimulation means for the creature. However, to begin with, there is no one at home in the brain to realise this potential, no one to take an interest in the meaning.

But, evolution is inventive. Before long there arises in the brain a special module—a proto self, if you like—whose job is exactly that: to discover “what the stimulation means for me”. And, as luck would have it, it turns out it can do this by the simple trick of reading—extracting the meaning from—the motor command signals being sent out to produce the reflex response.

So now, we have an agent who is reading the brain’s own responses and making a sensory interpretation of them. In truth this is the first subject of sensation. But let’s note there is nothing fancy or magical about the interpretation at this stage. The subjective experience does not have had any special phenomenal feel. What happened?

I’ve argued that the key lay in how sentition went on evolving. Back at the start, the reflex responses are overt bodily actions occurring at the site of stimulation at the body surface. However things are never going to stay like this. As the descendants of the original creatures evolve to be more sophisticated, these overt responses soon enough become inappropriate, even inconvenient—you don’t always want to grimace when you’re touched by red light, say. So now the creature faces a problem. How to lose the bodily behaviour but keep the information about the meaning of the stimulus?

The solution natural selection hits on is ingenious. It is for the responses to become internalised, or “privatised”, such that the motor signals no longer reach the actual body surface, but rather begin to target the body-map where the sense organs first project to the brain. Thus sentition evolves from being an actual form of bodily expression to being a virtual one—yet still a response that the subject can milk for information.


It should be noted that he chose "ipsundrum" as a rhyme with conundrum, ergo puzzle and the latin ipso for self. The puzzle of self, ergo ipsundrum is the solution to the puzzle of how the self sees and records the outside world.




In a single sentence Damasio and Lakoff have proposed that thinking is a kind of muscular activity. Sentition is the bridging idea as I perceive it. If the brain builds