Have you ever tried to describe the color red to someone who suffers from protanopia, deuteranopia, protanomaly, or deuteranomaly? It is nearly impossible since those who are red-green color blind are missing the corresponding photoreceptors. The experience of seeing red is so familiar to those who have experienced it. And that type of experience, one which is difficult to communicate, does not change based on other experiences, is unique to the individual experiencing it, and immediately recognized, is qualia. 

Frank Jackson offered the following definition of qualia;

Photo by Christian Stahl on Unsplash

[Qualia are] certain features of the bodily sensations especially, but also of certain perceptual experiences, which no amount of purely physical information includes.”

A few years later another philosopher/cognitive scientist Daniel Dennett, identified four properties ascribed to qualia; “ineffable”, “intrinsic”, “private”, and “directly or immediately apprehensible in consciousness” (Tye 2002, 447). In simpler language, qualia is a word describing the properties associated with how something was experienced. The qualia of “seeing red” may be difficult to describe on their own but when compared to the qualia of “seeing green” they can be conceptualized and contrasted. That is often called “spectrum inversion” and a famous example was presented by John Locke in “Of True and False Ideas” :

Portrait of John Locke
By Godfrey Kneller – State Hermitage Museum, St. Petersburg, Russia., Public Domain, https://commons.wikimedia.org/w/index.php?curid=1554640

Neither would it carry any Imputation of Falshood to our simple Ideas, if by the different Structure of our Organs, it were so ordered, That the same Object should produce in several Men’s Minds different Ideas at the same time; v.g. if the Idea, that a Violet produced in one Man’s Mind by his Eyes, were the same that a Marigold produces in another Man’s, and vice versâ. For since this could never be known: because one Man’s Mind could not pass into another Man’s Body, to perceive, what Appearances were produced by those Organs; neither the Ideas hereby, nor the Names, would be at all confounded, or any Falshood be in either. For all Things, that had the Texture of a Violet, producing constantly the Idea, which he called Blue, and those which had the Texture of a Marigold, producing constantly the Idea, which he as constantly called Yellow, whatever those Appearances were in his Mind; he would be able as regularly to distinguish Things for his Use by those Appearances, and understand, and signify those distinctions, marked by the Names Blue and Yellow, as if the Appearances, or Ideas in his Mind, received from those two Flowers, were exactly the same, with the Ideas in other Men’s Minds. 

(Byrne 2016)

These are very difficult concepts to teach an artificially intelligent agent. Concepts with very formal representations, like triangle or even something like a reptile are easier for artificially intelligent agents to differentiate. Things like “tastes salty” or “splitting headache” are very difficult to transfer to a learning agent since they are extremely personal. Whether or not quale exists is actively debated in the philosophical community. Especially in arguments around consciousness and self. I think that is why the exploration of qualia is so interesting to the development of AI. 

Girl touching the hand of a robot.
Photo by Andy Kelly on Unsplash

I think people like to explore what it could be like for robots with general intelligence to be sentient. But to develop those qualities, the engineer must examine the meta-cognitive processes that make up the human experience. This task is complicated and one that philosophers still argue about. What does it mean to be human? That question will need to be explored further in order to get closer to general artificial intelligence. In the mean time I invite you to make a mental note of the next time you try and describe qualia to someone else. What analogies did you use? How similar do you think the same experience is for both of you? 


  • Byrne, Alex, “Inverted Qualia”, The Stanford Encyclopedia of Philosophy (Winter 2016 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/win2016/entries/qualia-inverted/>.
  • Tye, M., 2002, “Visual Qualia and Visual Content Revisited”, in Philosophy of Mind, D. Chalmers (ed.), Oxford: Oxford University Press.

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