(consciousness redux) Rendering the Visible Invisible Clever experiments reveal how unconscious mechanisms can affect our brain and our behavior BY CHRISTOF KOCH WHAT IS CONSCIOUSNESS? What he didn’t have the body he thought he brain. An immense number of psycho- is this ineffable, subjective stuff—this had, maybe he had fake memories logical, medical, neurobiological and thing, substance, process, energy, soul, (premonitions of The Matrix), but be- physical stories about consciousness whatever—that you experience as the cause he was conscious he must exist. can now be told. Each Consciousness sounds and sights of life, as pain or as Yet the questions go on. Are only Redux essay will illuminate one facet pleasure, as anger or as the nagging feel- people conscious? What about a fetus? of one of the most central, enduring ing at the back of your head that maybe What about a neurological patient in and puzzling aspects of the world, you’re not meant for this job after all. a persistent vegetative state, such as subjective feelings. The question of the nature of con- Terri Schiavo (who died in 2005), who I am a scientist who seeks rational sciousness is at the heart of the ancient can’t do much more than open and explanations of ineffable conscious- mind-body problem. How does subjec- close her eyes? Although many are ness and of how and why it arises in tive consciousness relate to the objec- willing to accord sentience, conscious- the brain. But I also realize that our tive universe, to matter and energy? ness, to our beloved cats and dogs, universe is a strange place; there are Consciousness is the only way we what about apes, monkeys, whales, more things in heaven and earth than experience the world. Without it, you mice, bees and all the other critters on are dreamt of in philosophy. So I try to would be like a sleepwalker in a deep, the planet? Can a fly be conscious? be humble when it comes to one of the dreamless sleep, acting in the world, What about artificial consciousness? most mystifying aspects of this uni- speaking, having babies, but without Is your cool iPhone sentient? Can ma- verse—that I wake up each day and feeling anything. You would feel noth- chines ever become conscious, as is find myself conscious, capable of see- ing, nada, nichts, rien. Indeed, in the widely assumed in so many science- ing, touching, loving, feeling and re- most famous deduction of Western fiction novels and movies? membering. I am not a zombie! Many thought, philosopher and mathemati- Until recently, these questions were different traditions besides the mod- cian René Descartes concluded that purely within the domain of specula- ern scientific one have provided an- ) because he was conscious he existed. tive philosophy and fantasy. But over swers, and we should not reject them That was his only unassailable proof the past decades, science has been out of hand but listen to them. that he wasn’t just a chimera. Maybe making huge strides in exploring the Unconscious Influences As I write these lines, I am flying Stationary image Random flashed patterns in one eye in the other eye back from the annual meeting of the angry-faceexperiment Association for the Scientific Study of Consciousness that took place, this CHIYA ( U S year, in Taipei, Taiwan. It’s a gathering T U of hard-nosed philosophers, neurolo- G U gists, psychologists and neuroscientists TS O A concerned with consciousness. One of N F its high points is an annual award, O named in honor of the father of Ameri- can psychology. The 2008 William RTESY James Prize for Contributions to the ou Study of Consciousness went to Nao- ); C tsugu Tsuchiya, a young neurobiologist Koch from the California Institute of Tech- ( AN K S nology. What had he done that caught U N A constantly changing set of colored and overlaid rectangles projected into the attention of the prize committee? O one eye (right) suppresses a static image of an angry face shown to the other In 2005 Tsuchiya invented a tech- eye (left). An observer with both eyes open sees only the flickering mosaic. K ATMA nique, continuous flash suppression, F 18 SCIENTIFIC AMERICAN MIND October/November 2008 The mind has many nooks and crannies; some are accessible, ( but most are hidden from introspection. ) which renders a picture invisible, hid- A photograph of a naked wom- ing it from your conscious sight. Yet an or man is shown to the left some part of your brain has access to of the gaze in one eye while a the image and influences your behav- scrambled version of the same ior in untold ways. The way it works is image is shown to the right of simple. Say Tsuchiya wants to camou- the gaze. Both images are hid- den from conscious sight by flage a picture of an angry male face. the ever changing, evanescent With the help of a split computer colored shapes. Yet sensitive screen, Tsuchiya projects a faint image measurements show that of this snarling guy into your left eye. an observer does attend, Your right eye sees a rapidly changing un consciously, to the invisible set of colored rectangles, one on top of photograph depending on the another [see illustration on opposite observer’s own gender and page]. If you keep both eyes open, all sexual orientation. you see are the ever changing series of colored patches but no angry face. The constantly flickering colors attract anything but flashes of color. The psy- periment is scary because it seems as if your attention in a way that the static chologists asked the volunteers to people’s sexual orientation could be portrait does not. As soon as you close guess whether the naked person was in inferred (statistically) from their un- your right eye, the face becomes visi- the left or the right part of the image. conscious attentional biases. An ex- ble. But otherwise you have no inkling But they couldn’t. Their guesses were ample of the unconscious mind at that the face is there, even though your no better than chance. work. Freud would have loved it. left eye has been staring at it for many He and Jiang demonstrated that What this experiment teaches us is minutes. You simply do not see it. So the observers attended to the naked that the mind has many nooks and what is the big deal? picture but not to its scrambled coun- crannies; some—probably the minori- terpart. Even more interesting, straight ty—are consciously accessible, whereas Subconsciously Active males attended to pictures of naked most are hidden from introspection, Functional brain imaging shows women but were slightly repelled by lost in the vast catacombs of the brain. that this angry face still activates a pictures of naked men. Straight wom- Yet they can powerfully influence your part of your brain that is concerned en were attracted to pictures of naked behavior, making you do things with- with fear, the amygdala. That is, at men without showing a consistent re- out knowing why. Continuous flash least some sector of your brain knows pulsion for pictures of naked women. suppression—and other techniques that about the face—as it ought to because Gay men behaved much like straight magicians and psychologists have in- an angry male face in front of you women; they unconsciously paid at- vented to distract you so you do not see might spell big trouble. This brain ac- tention to the pictures of the naked things while looking at them—in com- tivity remains unconscious but may men but not to those of women. What bination with functional brain imaging ) influence your behavior or generate a is disconcerting about this experiment is a delicate tool to map the landscape subtle feeling of unease. is that this all took place outside the of the visual unconscious. M Using this technique, psychologist pale of consciousness. Because the ob- Sheng He, with his student Yi Jiang servers never actually saw the naked CHRISTOF KOCH is Lois and Victor Troendle and their colleagues at the University images, they had no idea they were at- Professor of Cognitive and Behavioral Biolog y of Minnesota, made an intriguing dis- tracted or repelled by them. This ex- at the California Institute of Technology. covery. They projected to one eye a naked-woman experiment naked-woman E ( photograph of a naked person on one H (Further Reading) side of the gaze and a scrambled ver- u Continuous Flash Suppression Reduces Negative Afterimages. N. Tsuchiya and C. Koch HENG sion of the same image on the other in Nature Neuroscience, Vol. 8, No. 8, pages 1096–1101; August 2005. S F u A Gender- and Sexual Orientation-Dependent Spatial Attentional Effect of Invisible O side. They then hid both using contin- uous flash suppression see[ illustration I m a g e s . Y. Jiang, P. Costello, F. Fang, M. Huang and S. He in Proceedings of the National Academy of Sciences USA, Vol. 103, No. 45, pages 17048–17052; November 7, 2006. RTESY above]. The paid volunteers who par- u Web site of the Association for the ScientificS tudy of Consciousness: ou C ticipated in the experiment never saw www.assc.caltech.edu www.SciAmMind.com SCIENTIFIC AMERICAN MIND 19.