Sentience Quotient [was Re: qualia]

Robert J. Bradbury (
Thu, 2 Dec 1999 11:59:54 -0800 (PST)

On Thu, 2 Dec 1999, Robin Hanson wrote:

> It seems to me that the essential question is: "What does it
> feel like to be a rock?" Or a star, or a plant, etc. We know
> it feels like something to be living humans, at least we
> presume this is true for most of us. So either:
> 1) Everything has something it feels like to be it, or
> 2) Only some things have something if feels like to be them.
> If 1, my question about rocks makes sense. If 2, then
> we face the hard question of which things feel and which
> things don't. As far as I can tell, no one is anywhere close
> to answering these questions.

I think Robert Freitas has taken a first step in this direction. Chapter 14 (Extraterrestrial Intelligence) of his Xenology (unpublished book) has a discussion about a "Sentience Quotient" based on Bremermann's information density limits.

"...Sentience Quotient... [is] The maximum bit rate a sentient creature can process per unit time interval (in bits/second), divided by the quantity of mass-energy the entity needs to do it (in kilograms).

Given Bremermann's limits, the maximum sentience quotient is (log_10(1.4 x 10^50) or 50. He estimates that humans have a sentience quotient of around 10 (10^10 bits/sec-kg). Since a rock has a very low bit processing rate (probably directly related to temperature gradients in it), it probably has a very low SQ. A plant on the other hand since it is moving fluids around and turning genes on and off might get a SQ of 4-6. (You might expect a higher number given the number of cells but you have to adjust for the redundancy where there is no "extra" information being processed.) A Matrioshka Brain gets a SQ someplace in the range of 15-20.

To get a SQ higher than 20, I think you have to do away with much of the matter and compute using quantum interactions with things like free neutrons, single electrons, neutrinos or free photons. Within our foreseeable future it looks like only single electrons or photons are very likely. Even then things look pretty difficult because most current approaches require a large amount of external matter to manipulate these "objects". You might be able to get a high SQ in a photon "gas", but you are cheating if you neglect the mass of material required to produce that state.

So to the degree that "qualia" == "feelings" == "SQ" we do have a way of quantifying it.