Making Sense of Hallucination: Degrees of Veridicality in Perceptual Experience Link Swanson (Center for Cognitive Sciences, University of Minnesota, Minneapolis, MN ) C11
What is the difference between perception and hallucination? In this talk I offer a conceptual framework for making sense of the varieties of perceptual experience, including veridical perception, illusion, and hallucination. I call this framework the "S-hallucination theory of perception" or SHTOP. I argue that our philosophical criteria of what makes a perception veridical must avoid relying on so-called "mind-independent" objects. All objects in perceptual experience, including those in veridical experience, I argue, are mind-dependent?produced in the mind, generated by the brain. I point out that we have no problem at all accepting that the objects in hallucinatory experience are produced in the mind. I argue that this is the correct way to think about the perceptual objects presented in standard everyday veridical experience as well. Importantly, I do not claim that all perception is merely hallucination nor do I demote reality to mere illusions on the fancy. To the contrary, my framework makes a positive contribution by offering a simple set of purely phenomenological, ontologically subjective criteria that allow us to demarcate veridical perception from hallucination and uphold a meaningful distinction between reality and fantasy. I call these criteria "S-traits" and bake them into a simple metric I call the "S-factor metric" which I claim can be used to gauge the veridicality of any given experience. All perceptual experience is mind-dependent, yet nonetheless some experiences have "more reality in them" than others. My project aims to work out the implications of the now-trendy adage "perception is controlled hallucination" which has been promoted (by Anil Seth) in recent popular media appearances. First, I trace the historical roots of similar notions from neuroscientists like Dale Purves, Chris Frith, and Donald Hoffman; to philosophers like Andy Clark, Thomas Metzinger, and John Smythies; to early computer vision pioneers like Max Clowes and Geoffrey Hinton; and back further to early neurologists like Heinrich Klover and Hermann von Helmholtz; and further yet to early-modern philosophers Kant, Hume, and Berkeley. Next, I present the facts about perceptual experience which motivate this thinking, including ordinary everyday perception as well as nonordinary experience, with a focus on issues raised by psychedelic drug effects. Finally, I briefly situate the notion against major positions in philosophy of perception, including direct/naive realism, sense-data theory, intentionalism, disjunctivism, and idealism. My unique contribution is to render the trendy "perception is controlled hallucination" catchphrase as a historically informed, scientifically responsible, phenomenologically accurate, philosophically workable position for 21st-century cognitive science.