The Nonlinear Library EA - Only mammals and birds are sentient, according to neuroscientist Nick Humphrey's theory of consciousness, recently explained in "Sentience: The invention of consciousness" by ben.smith
Dec 27, 2023
14:28
Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Only mammals and birds are sentient, according to neuroscientist Nick Humphrey's theory of consciousness, recently explained in "Sentience: The invention of consciousness", published by ben.smith on December 27, 2023 on The Effective Altruism Forum.
In 2023, Nick Humphrey published his book Sentience: The invention of consciousness (S:TIOC). In this book he proposed a theory of consciousness that implies, he says, that only mammals and birds have any kind of internal awareness.
His theory of consciousness has a lot in common with the picture of consciousness is described in recent books by two other authors, neuroscientist Antonio Damasio and consciousness researcher Anil Seth. All three agree on the importance of feelings, or proprioception, as the evolutionary and experiential base of sentience. Damasio and Seth, if I recall correctly, each put a lot of emphasis on homeostasis as a driving evolutionary force.
All three agree sentience evolved as an extension of our senses-touch, sight, hearing, and so on. But S:TIOC is a bolder book which not only describes what we know about the evolutionary base of consciousness but proposes a plausible theory coming as close as can be to describing what it is short of actually solving Chalmers' Hard Problem.
The purpose of this post is to describe Humphrey's theory of sentience, as described in S:TIOC, and explain why Humphrey is strongly convinced that mammals and birds-not octopuses, fish, or shrimp-have any kind of internal experience. Right up front I want to acknowledge that cause areas focused on animals like fish and shrimp seem on-expectation impactful even if there's only a fairly small chance those animals might have capacity for suffering or other internal experiences.
Those areas might be impactful because of the huge absolute numbers of fish and shrimp who are suffering if they have any internal experience at all. But nevertheless, a theory with reasonable odds of being true that can identify which animals have conscious experience should update us on our relative priorities. Furthermore, if there is substantial uncertainty, which I think there is, such a theory should motivate hypothesis testing to help us reduce uncertainty.
Blindsight
To understand this story, you should hear about three fascinating personal encounters which lead Humphrey to some intuitions about consciousness. Humphrey describes blindsight in a monkey and a couple of people. Blindsight is the ability for an organism to see without conscious awareness of seeing. Humphrey tells of a story of a monkey named Helen whose visual cortex had been removed.
Subsequent to the removal of her visual cortex, Helen was miserable and unmotivated to move about in the indoor world she lived in. After a year of this misery, her handlers allowed her to get out into the outside world and explore it. Over the course of time she learned to navigate around the world with an unmistakable ability to see, avoid obstacles, and quickly locate food.
But Humphrey, knowing Helen quite well, thought she lacked the confidence in herself to be able to have the awareness that she clearly did. This was a clue that perhaps Helen was using her midbrain system, the superior colliculus, which processes visual information in parallel with the visual cortex, and that she was unaware of the visual information her brain could nevertheless use to navigate her body around obstacles and to locate food. Of course this is somewhat wild speculation considering that Helen couldn't report her own experience back to Humphrey.
The second observation was of a man known to the scientific community as D.B. In an attempt to relieve D.B. of terribly painful headaches, doctors had removed D.B.'s right visual cortex. D.B. reported not being able to see anything presented only to his left eye (the left and ...
In 2023, Nick Humphrey published his book Sentience: The invention of consciousness (S:TIOC). In this book he proposed a theory of consciousness that implies, he says, that only mammals and birds have any kind of internal awareness.
His theory of consciousness has a lot in common with the picture of consciousness is described in recent books by two other authors, neuroscientist Antonio Damasio and consciousness researcher Anil Seth. All three agree on the importance of feelings, or proprioception, as the evolutionary and experiential base of sentience. Damasio and Seth, if I recall correctly, each put a lot of emphasis on homeostasis as a driving evolutionary force.
All three agree sentience evolved as an extension of our senses-touch, sight, hearing, and so on. But S:TIOC is a bolder book which not only describes what we know about the evolutionary base of consciousness but proposes a plausible theory coming as close as can be to describing what it is short of actually solving Chalmers' Hard Problem.
The purpose of this post is to describe Humphrey's theory of sentience, as described in S:TIOC, and explain why Humphrey is strongly convinced that mammals and birds-not octopuses, fish, or shrimp-have any kind of internal experience. Right up front I want to acknowledge that cause areas focused on animals like fish and shrimp seem on-expectation impactful even if there's only a fairly small chance those animals might have capacity for suffering or other internal experiences.
Those areas might be impactful because of the huge absolute numbers of fish and shrimp who are suffering if they have any internal experience at all. But nevertheless, a theory with reasonable odds of being true that can identify which animals have conscious experience should update us on our relative priorities. Furthermore, if there is substantial uncertainty, which I think there is, such a theory should motivate hypothesis testing to help us reduce uncertainty.
Blindsight
To understand this story, you should hear about three fascinating personal encounters which lead Humphrey to some intuitions about consciousness. Humphrey describes blindsight in a monkey and a couple of people. Blindsight is the ability for an organism to see without conscious awareness of seeing. Humphrey tells of a story of a monkey named Helen whose visual cortex had been removed.
Subsequent to the removal of her visual cortex, Helen was miserable and unmotivated to move about in the indoor world she lived in. After a year of this misery, her handlers allowed her to get out into the outside world and explore it. Over the course of time she learned to navigate around the world with an unmistakable ability to see, avoid obstacles, and quickly locate food.
But Humphrey, knowing Helen quite well, thought she lacked the confidence in herself to be able to have the awareness that she clearly did. This was a clue that perhaps Helen was using her midbrain system, the superior colliculus, which processes visual information in parallel with the visual cortex, and that she was unaware of the visual information her brain could nevertheless use to navigate her body around obstacles and to locate food. Of course this is somewhat wild speculation considering that Helen couldn't report her own experience back to Humphrey.
The second observation was of a man known to the scientific community as D.B. In an attempt to relieve D.B. of terribly painful headaches, doctors had removed D.B.'s right visual cortex. D.B. reported not being able to see anything presented only to his left eye (the left and ...