A human neuron has an average mass of about 10-10 kg and one neuron can process 1000-3000 bits/sec. earning us an SQ rating of +13. What is most interesting here is not the obvious fact that there's a great deal of room for improvement (there is!), but rather that all "neuronal sentience" SQs, from insects to mammals, cluster within several points of the human value. From the cosmic point of view, rotifers, honeybees, and humans all have brainpower with roughly equivalent efficiencies. Note that we are still way ahead of the computers, with an Apple II at SQ +5 and even the mighty Cray I only about +9. the fundamental upper limit to brain efficiency is imposed by the laws of quantum mechanics: all information, to be acted upon, must be represented physically and be carried by matter-energy "markers." According to the Uncertainty Principle in quantum mechanics, the lower limit for the accuracy with which energy can be measured—the minimum measurable energy level for a marker carrying one bit–is given by Planck's constant h divided by T, the duration of the measurement. If one energy level is used to represent one bit, then the maximum bit rate of a brain is equal to the total energy available E ( = mc02) for representing information, divided by the minimum measurable energy per bit (h/T) divided by the minimum time required for readout (T): mc02/h = 1050 (bit/s)/kg. Hence the maximum possible SQ is +50.
How about intelligences greater than human? Astronomer Robert Jastrow and others have speculated that silicon-based computer brains may represent the next and ultimate stage in our evolution. This is valid, but only in a very limited sense. Superconducting Josephson junction electronic gates weigh 10-12 kg and can process 1011 bits/sec, so "electronic sentiences" made of these components could have and SQ of +23 – ten orders beyond man. But even such fantastically advanced systems fall short of the maximum of +50. Somewhere in the universe may lurk beings almost incomprehensible to us, who think by manipulating atomic energy levels and are mentally as far beyond our best future computers as those computers will surpass the Venus flytrap.
Just as consciousness is an emergent of neuronal sentience, perhaps some broader mode of thinking–call it communalness–is an emergent of electronic sentience. If this is true, it might help to explain why (noncommunal) human beings have such great difficulty comprehending the intricate workings of the societies, governments, and economies they create, and require the continual and increasing assistance of computers to juggle the thousands of variables needed for successful management and planning. Perhaps future computers with communalness may develop the same intimate awareness of complex organizations as people have consciousness of their own bodies. And how many additional levels of emergent higher awareness might a creature with SQ +50 display?
The possible existence of ultrahuman SQ levels may affect our ability, and the desirability, of communicating with extraterrestrial beings. Sometimes it is rhetorically asked what we could possibly have to say to a dog or to an insect, if such could speak, that would be of interest to both parties? From our perspective of Sentience Quotients, we can see that the problem is actually far, far worse than this, more akin to asking people to discuss Shakespeare with trees or rocks. It may be that there is a minimum SQ "communication gap," an intellectual distance beyond which no two entities can meaningfully converse.
At present, human scientists are attempting to communicate outside our species to primates and cetaceans, and in a limited way to a few other vertebrates. This is inordinately difficult, and yet it represents a gap of at most a few SQ points. The farthest we can reach is our "communication" with vegetation when we plant, water, or fertilize it, but it is evident that messages transmitted across an SQ gap of 10 points or more cannot be very meaningful.
What, then, could an SQ +50 Superbeing possibly have to say to us?