Rendering the Visible Invisible

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					 (consciousness redux)

 Rendering the Visible
 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-

                                                                                                                                          fat m a KO n U s K a n ( Ko c h ) ; c O U r t e s y O f n aO t s U g U t s U c h i ya ( a n g r y - f a c e e x p e r i m e n t )
 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
      stationary image                                                                       As I write these lines, I am flying
                                               random flashed patterns
         in one eye                                in the other eye                      back from the annual meeting of the
                                                                                         Association for the Scientific Study of
                                                                                         Consciousness that took place, this
                                                                                         year, in Taipei, Taiwan. It’s a gathering
                                                                                         of hard-nosed philosophers, neurolo-
                                                                                         gists, psychologists and neuroscientists
                                                                                         concerned with consciousness. One of
                                                                                         its high points is an annual award,
                                                                                         named in honor of the father of Ameri-
                                                                                         can psychology. The 2008 William
                                                                                         James Prize for Contributions to the
                                                                                         Study of Consciousness went to Nao-
                                                                                         tsugu Tsuchiya, a young neurobiologist
                                                                                         from the California Institute of Tech-
                                                                                         nology. What had he done that caught
A constantly changing set of colored and overlaid rectangles projected into              the attention of the prize committee?
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.             nique, continuous flash suppression,

 18   scientific american mind                                                                      O c to b e r/ n ove m b e r 2 0 0 8
                                                  (  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                                                           unconsciously, 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
cOUrtesy Of sheng he (naked - woman experiment)

                                                  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 Biology
                                                  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
                                                  photograph of a naked person on one         (Further Reading)
                                                  side of the gaze and a scrambled ver-       u Continuous Flash Suppression Reduces Negative Afterimages. n. tsuchiya and c. Koch
                                                  sion of the same image on the other           in Nature Neuroscience, Vol. 8, no. 8, pages 1096–1101; august 2005.
                                                  side. They then hid both using contin-      u A Gender- and Sexual Orientation-Dependent Spatial Attentional Effect of Invisible
                                                                                                Images. y. Jiang, P. costello, f. fang, m. huang and s. he in Proceedings of the National
                                                  uous flash suppression [see illustration      Academy of Sciences USA, Vol. 103, no. 45, pages 17048–17052; november 7, 2006.
                                                  above]. The paid volunteers who par-        u Web site of the association for the scientific study of consciousness:
                                                  ticipated in the experiment never saw

                                                  w w w. s c i a m m in d .c o m                                                                scientific american mind               19

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