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Comparative sentience: what does it mean to be smart?

Comparing the relative sentience of human and non-human intelligences starts with defining the aspects of sentience, even before you break them down into specific characteristics.

I’ve brought this post over from Medium because it was cited in December 2022 by Maurice Yolles at Liverpool John Moores University for Consciousness, Sapience and Sentience—A Metacybernetic View in the journal Systems.

I previously sketched an overview of imagining a measure of Comparative Sentience, and the first task I identified was a set of semantic challenges.

  • What are sentience, sapience, consciousness, intelligence and emotion?
  • What are the differences and similarities between these aspects?
  • Do we need to measure and compare some or all of them?
  • Is sentience the best overall term?
A chimpanzee with a tool

1. Sentience

The Oxford English Dictionary offers a surprisingly narrow definition of sentience as “the ability to perceive or feel things”, while Merriam-Webster is slightly more helpful with “feeling or sensation as distinguished from perception and thought”.

In the philosophy of animal rights, sentience is a reference to subjective experiences, which crucially includes the capacity to experience pain and pleasure, and animal sentience is recognised in the EU’s 1997 Treaty of Amsterdam.

There is a proposed comparative measure of sentience. The Sentience Quotient was coined by the molecular engineering researcher Robert A Freitas Jr in 1977 and defines sentience as the relationship between the information processing rate (bit/s) of each individual processing unit (such as a neuron), the weight and size of a single unit and the total number of processing units (expressed as mass). It’s a measure of efficiency which makes humans almost identical to primates and little different to insects, but it’s of little use here because it says nothing about the quality of sentient experience.

2. Sapience

The OED and M-W dictionaries both describe sapience interchangeably with wisdom and sagacity: “Having or showing experience, knowledge, and good judgement”, although Collins is more expansive: “the ability or result of an ability to think and act utilizing knowledge, experience, understanding, common sense, and insight”.

Arguably, the use of information integrated from different types of experience is the distinctively human feature which justifies the title of homo sapiens, encompassing other aspects of intelligence such as the culture and communication required to build a body of knowledge, understanding those around us, and understanding how to manipulate the environment.

Not surprisingly, wisdom is highly regarded by religions, either as a facet of godhood of which humans can only achieve a limited portion, or as the path to ultimate enlightenment and godhood.

3. Consciousness

One of the great mysteries of philosophy isn’t going to be settled in a blog post: there is no widely accepted operational definition of consciousness, or how and why it exists, but it is something that everyone agrees people have, and it is probably present in some animals.

The OED calls consciousness “the state of being aware of and responsive to one’s surroundings” and “the fact of awareness by the mind of itself and the world”. Merriam-Webster gives a range of definitions, most usefully “the quality or state of being aware especially of something within oneself”, “the state of being characterized by sensation, emotion, volition, and thought” and “the upper level of mental life of which the person is aware as contrasted with unconscious processes”.

While some of this is a broader version of sentience, the key aspects that make consciousness different from sentience seem to be self-awareness and the contrast with unconscious activity.

Philosophers continue to argue that there are different types and forms of consciousness, which might allow us to form a hierarchy of consciousness if these states can be measured and tested across species. The problem is that consciousness is at least partially subjective, so we would have to accept that any being which communicates an understanding of the concept and claims ownership of it is, therefore, conscious.

In the absence of direct communication, psychologists typically use the mirror test to establish self-awareness, and have found it across a wide range of species to a degree which may even be quantifiable. Behavioural tests can demonstrate both volition and a theory of mind to different degrees across apes, monkeys, and other animals.

4. Intelligence

Often defined broadly, the OED says intelligence is “the ability to acquire and apply knowledge and skills” while M-W defines it as “ the ability to learn or understand or to deal with new or trying situations” and “the ability to apply knowledge to manipulate one’s environment or to think abstractly as measured by objective criteria”.

While the aspects of knowledge and awareness are similar to sapience, intelligence is distinguished by analysis and the application of knowledge to solve problems, which require volition and planning, and may require innovation too.

5. Emotion

While M-W gives a simple definition as “the affective aspect of consciousness” it helpfully provides a more complex one: “a conscious mental reaction (as anger or fear) subjectively experienced as strong feeling usually directed toward a specific object and typically accompanied by physiological and behavioral changes in the body”. OED is illuminatingly different: “Instinctive or intuitive feeling as distinguished from reasoning or knowledge” or “A strong feeling deriving from one’s circumstances, mood, or relationships with others”.

The crucial aspect for this project is that emotion is a conscious experience, not just a reaction such as retreating from a source of pain, but at the same time, it is separate from sapience or intelligence. It’s worth including in this project because it has a role in learning and volition, and because there’s a large body of work on emotions in humans and animals, although there’s also a great deal of debate about whether non-human animals experience emotional states in the same way as humans, and the role of cognition in human emotional experiences.

Common factors in aspects of sentience
Common semantic factors in aspects of sentience.


Looking at the common factors which emerge between the different aspects of sentience, it’s interesting that subjective experience is common to all except intelligence, while sentience shares all of its factors with sapience, consciousness and emotion.

No single aspect emerges as dominant, and intelligence sits apart from emotion (not surprisingly). The most effective approach seems to be to stick with Comparative Sentience.

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