Sleights Of Mind Part 13

How stereopsis is actually accomplished in the brain remains one of the deepest mysteries of visual neuroscience. We know a bit, but relatively little compared to what we know about how other processes, such as motion perception, are accomplished. We know that the information from each eye remains segregated at the level of your optic nerves. We also know that visual information from your two eyes converges onto the same neurons in your primary visual cortex. This means that certain neurons in this brain region can respond to stimuli from either eye or both eyes. They are binocular.

But where in the brain does vision, based on both eyes, come together? Where is the depth of each object in the scene computed? Where do the images fuse into one seamless experience? We know these things must happen. Otherwise we would have double vision instead of depth perception. In our own labs, we have found that the processes used to derive stereoscopic perception must arise several levels above the primary visual cortex in the visual hierarchy. Finding the exact location is an area of active research.

Stereopsis contributes to Vernon's trick, too, because your two eyes see your card pushed into the deck from different angles. Your brain triangulates these two different retinal images to compute the depth of the card within the deck. It's an illusion, but stereopsis confirms that the card is mid-deck.

Tony took advantage: A. S. Barnhart (in press), "The exploitation of Gestalt principles by magicians," Perception.

Good continuation is so integral to a plethora of brain mechanisms: Ibid.

saws a woman in half: This trick can be accomplished in other ways as well. But in all of them good continuation plays a role in the effect.

Charles Gilbert and colleagues: M. K. Kapadia, M. Ito, C. D. Gilbert, and G. Westheimer (1995), "Improvement in visual sensitivity by changes in local context: Parallel studies in human observers and in V1 of alert monkeys," Neuron 15: 84356.

A second concept behind the spoon illusion: It has been published as the "Dancing Bar" illusion by Peter Tse and Brown Hsieh at Dartmouth College. The neural basis of this illusion has been shown by Christopher Pack, now at the Montreal Neurological Inst.i.tute. P. U. Tse, P.-J. Hsieh (2007), "Component and intrinsic motion integrate in 'dancing bar' illusion," Biological Cybernetics 96(1): 18; C. C. Pack and R. T. Born (2001), "Temporal dynamics of a neural solution to the aperture problem in visual area MT of macaque brain," Nature 409: 104042.

To localize the ends of a line: C. C. Pack, M. S. Livingstone, K. R. Duffy, and R. T. Born (2003), "End-stopping and the aperture problem: Two-dimensional motion signals in macaque V1," Neuron 39: 67180.

3. The Brother Who Faked a Dome For further discussion on how visual art and visual science interact, see S. Martinez-Conde and S. L. Macknik (2010), "Art as Visual Research: Kinetic Illusions in Op Art," Scientific American Special 20(1): 4855.

Susana's results showed instead: X. G. Troncoso, S. L. Macknik, and S. Martinez-Conde (2005), "Novel visual illusions related to Vasarely's 'nested squares' show that corner salience varies with corner angle," Perception 34: 40920; X. G. Troncoso, P. U. Tse, S. L. Macknik, G. P. Caplovitz, P.-J. Hsieh, A. A. Schlegel, J. Otero-Millan, and S. Martinez-Conde (2007), "BOLD activation varies parametrically with corner angle throughout human retinotopic cortex," Perception 36: 80820; X. G. Troncoso, S. L. Macknik, and S. Martinez-Conde (2009), "Corner salience varies linearly with corner angle during flicker-augmented contrast: A general principle of corner perception based on Vasarely's artworks," Spatial Vision 22: 21124.

In 2006 we designed an experiment: X. G. Troncoso, S. L. Macknik J. Otero-Millan, and S. Martinez-Conde (2008), "Microsaccades drive illusory motion in the Enigma illusion," Proceedings of the National Academy of Sciences of the United States of America[hereafter PNAS] 105: 1603338.

Her expression is often: M. S. Livingstone (2000), "Is it warm? Is it real? Or just low spatial frequency?" Science 290: 1299.

The Leaning Tower illusion: F. A. A. Kingdom, A. Yoonessi, and E. Gheorghiu (2007), "The Leaning Tower illusion: A new illusion of perspective," Perception 36(3): 47577.

The only difference between these two faces: R. Russell (2009), "A s.e.x difference in facial pigmentation and its exaggeration by cosmetics," Perception 38: 121119.

Some stationary patterns: A. Kitaoka, Trick Eyes: Magical Illusions That Will Activate the Brain (New York: Sterling Publishing, 2005).

We called the new illusion: S. L. Macknik and M. S. Livingstone (1998), "Neuronal correlates of visibility and invisibility in the primate visual system," Nature Neuroscience 1(2): 14449; S. L. Macknik and M. M. Haglund (1999), "Optical images of visible and invisible percepts in the primary visual cortex of primates," PNAS 96: 1520810; S. L. Macknik, S. Martinez-Conde, and M. M. Haglund (2000), "The role of spatiotemporal edges in visibility and visual masking," PNAS 97: 755660; S. L. Macknik and S. Martinez-Conde (2004), "Dichoptic visual masking reveals that early binocular neurons exhibit weak interocular suppression: Implications for binocular vision and visual awareness," Journal of Cognitive Neuroscience 16: 104959; P. U. Tse, S. Martinez-Conde, A. A. Schlegel, and S. L. Macknik (2005), "Visibility, visual awareness, and visual masking of simple unattended targets are confined to areas in the occipital cortex beyond human V1/V2," PNAS 102: 1717883; S. L. Macknik (2006), "Visual masking approaches to visual awareness," Progress in Brain Research 155: 177215; S. L. Macknik and S. Martinez-Conde (2007), "The role of feedback in visual masking and visual processing," Advances in Cognitive Psychology 3: 12552; S. L. Macknik and S. Martinez-Conde, "The Role of Feedback in Visual Attention and Awareness," in M. S. Gazzaniga, ed., The Cognitive Neurosciences (Cambridge, Ma.s.s.: MIT Press, 2009), pp. 116579.

4. Welcome to the Show One critical clue: T. Moore and M. Fallah (2004). "Microstimulation of the frontal eye field and its effects on covert spatial attention," Journal of Neurophysiology 91: 15262; Z. M. Hafed and R. J. Krauzlis (2010), "Microsaccadic suppression of visual bursts in the primate superior colliculus," Journal of Neuroscience 30(28): 954247; N. L. Port and R. H. Wurtz (2009), "Target selection and saccade generation in monkey superior colliculus," Experimental Brain Research 192(3): 46577; J. W. Bisley and M. E. Goldberg (2010), "Attention, intention, and priority in the parietal lobe," Annual Review of Neuroscience 33: 121.

Other times you can shift your attention around: Study by Keisuke f.u.kada and Edward K. Vogel, "Human variation in overriding attentional capture," Journal of Neuroscience, July 8, 2009.

Research shows that: G. F. Woodman and S. J. Luck (2007), "Do the contents of visual working memory automatically influence attentional selection during visual search?" Journal of Experimental Psychology: Human Perception and Performance 33(2): 36377.

"retinotopic" s.p.a.ce: R. Desimone and J. Duncan (1995), "Neural mechanisms of selective visual attention," Annual Review of Neuroscience 18: 193222.

Jose-Manuel Alonso: Our work with Jose-Manuel Alonso also showed that a specific kind of neuron is enhanced during attention in the center of the spotlight, while a different kind of neuron is inhibited during attention in the surrounding regions. The neurons with enhanced firing in the center of the attentional spotlight are known to inhibit other neurons, whereas the neurons with suppressed firing in the surrounding regions are critical to determining the direction of moving objects. These results suggest that the role of top-down attention in the very earliest stages of vision is to suppress the attention-grabbing aspects of objects moving around whatever it is you want to pay attention to. See Y. Chen, S. Martinez-Conde, S. L. Macknik, Y. Bareshpolova, H. A. Swadlow, and J.-M. Alonso (2008), "Task difficulty modulates the activity of specific neuronal populations in primary visual cortex," Nature Neuroscience 11: 97482.

Arturo de Ascanio: A. Ascanio, The Magic of Ascanio, vol. 1, trans. R. B. Etcheberry (self-published, 2007).

n.o.bel laureate Eric Kandel: E. Kandel, In Search of Memory: The Emergence of a New Science of Mind (New York: W.W. Norton, 2007).

Ethological studies: One evolutionary advantage of having a spotlight of attention dissociated from your center of gaze is that it enhances your ability to deceive others. Having a roving spotlight of attention that can point away from your direction of gaze allows you to hide what you are paying attention to (a potential food source, a desirable mate) from compet.i.tors. Marc Hauser at Harvard University has shown that monkeys will intentionally look away from hidden food sources in order to mislead other monkeys away from their stash. See M. D. Hauser (1992), "Costs of deception: Cheaters are punished in rhesus monkeys (Macaca mulatta)," PNAS 89(24): 1213739. The cost of this system is that attending away from the fovea is, by definition, attending to low resolution information. Therefore, hiding your secret interests from those around you must convey an important adaptive edge.

In this sense, both macaques: Many other species use deception to maximize survival and reproductive success. Some birds will feign having a broken wing to lure a predator away from the nest: a form of misdirection. Such pretense of weakness is an old strategy in human warfare. Sun Tzu wrote in The Art of War more than two thousand years ago: "All warfare is based on deception. Hence, when able to attack, we must seem unable; when using our forces, we must seem inactive; when we are near, we must make the enemy believe we are far away; when far away, we must make him believe we are near. Hold out baits to entice the enemy. Feign disorder, and crush him." Other animals rely on camouflage and mimicry for deceptive purposes: some nonpoisonous b.u.t.terflies evolved the same wing patterns as poisonous species, giving them the advantage of warning off predatory birds.

5. The Gorilla in Your Midst To overcome adaptation: S. Martinez-Conde and S. L. Macknik (2007), "Windows on the mind," Scientific American 297: 5663; S. Martinez-Conde, S. L. Macknik, X. G. Troncoso, and T. Dyar (2006), "Microsaccades counteract visual fading during fixation," Neuron 49: 297305.

You cannot predict: For a more in-depth discussion of these ideas, see S. Martinez-Conde and S. L. Macknik (2008), "Magic and the brain," Scientific American 299: 7279; S. L. Macknik, M. King, J. Randi, A. Robbins, Teller, J. Thompson, and S. Martinez-Conde (2008), "Attention and awareness in stage magic: Turning tricks into research," Nature Reviews Neuroscience 9: 87179.

To describe these methods: Macknik et al., "Attention and awareness in stage magic."

Cognitive neuroscientists: A. Mack and I. Rock, Inattentional Blindness (Cambridge, Ma.s.s.: MIT Press, 1998).

Can You Keep Us From Reading Your Mind?: From Martinez-Conde and Macknik "Magic and the brain."

Tamariz uses inattentional blindness: Details can be found in his instructional masterpiece, The Five Points of Magic.

Our own research: Y. Chen, S. Martinez-Conde, S. L. Macknik, Y. Bereshpolova, H. A. Swadlow, and J. M. Alonso (2008), "Task difficulty modulates the activity of specific neuronal populations in primary visual cortex," Nature Neuroscience 11: 97482.

The Gorilla in Our Midst experiment: For a wonderful and very entertaining in-depth look at this and related effects, see Chabris and Simons's new book, The Invisible Gorilla (New York: Crown Archetype, 2010).

In 2006, Daniel Memmert: D. Memmert (2006), "The effects of eye movements, age, and expertise on inattentional blindness," Consciousness and Cognition 15: 62027.

Inattentional blindness: I. E. Hyman Jr., M. Boss, B. M. Wise, K. E. McKenzie, and J. M. Caggiano (2010), "Did you see the unicycling clown? Inattentional blindness while walking and talking on a cell phone," Applied Cognitive Psychology 24: 597607.

Another of our colleagues: C. Rosen (2008), "The myth of mult.i.tasking," New Atlantis: A Journal of Technology and Society 20: 10510.

In one version: D. J. Simons and D. T. Levin (1998), "Failure to detect changes to people during a real-world interaction," Psychonomic Bulletin and Review 5: 64449. See also C. F. Chabris and D. J. Simons, The Invisible Gorilla (New York: Crown Archetype, 2010).

The experiment has been replicated many times: The British mentalist and magician Derren Brown loves change blindness and has made several video clips of the trick in London settings, based on the original Simons videos.

Slow or gradual changes: Chabris and Simons, The Invisible Gorilla.

6. The Ventriloquist's Secret Senses not only interact: This research was carried out by Charles Spence, head of the Crossmodal Research Laboratory based at the Department of Experimental Psychology, Oxford University (http://www.psy.ox.ac.uk/xmodal/default.htm). He is interested in how people perceive the world around them-in particular, how our brains manage to process the information from each of our senses (smell, taste, sight, hearing, and touch) to form the extraordinarily rich multisensory experiences that fill our daily lives. He currently works on problems a.s.sociated with the design of foods that maximally stimulate the senses, and with the effect of the indoor environment on mood, well-being, and performance.

The same goes for skin and sound: By mixing audio with the tactile sense of airflow, researchers at the University of British Columbia in Vancouver-linguistics professor Bryan Gick and his student Donald Derrick-found that perception of certain sounds relies, in part, on being able to feel these sounds. Their paper was published in Nature, November 26, 2009.

Your ears can also fool your eyes: L. Shams, Y. Kamitani, and S. Shimojo (2002), "Visual illusion induced by sound," Cognitive Brain Research 14: 14752.

In the same vein: V. Jousmaki and R. Hari (1998), "Parchment-skin illusion: Sound-biased touch," Current Biology 8(6): R190.

How you feel the world can actually change how you see it: This research was carried out in the lab of Chris Moore at MIT and was published in the April 9, 2009, online edition of Current Biology. Demos of the motion stimuli can be seen at http://web.mit.edu/~tkonkle/www/CrossmodalMAE.html.

And then there is the rubber hand illusion: M. Botvinick and J. Cohen (1998), "Rubber hands 'feel' touch that eyes see," Nature 391: 756.

The phenomenon is called synesthesia: R. E. Cytowic, Synesthesia: A Union of the Senses, 2nd ed. (Cambridge, Ma.s.s.: MIT Press, 2002); R. E. Cytowic, The Man Who Tasted Shapes (Cambridge, Ma.s.s.: MIT Press, 2003); R. E. Cytowic and D. M. Eagelman, Wednesday Is Indigo Blue: Discovering the Brain of Synesthesia (Cambridge, Ma.s.s.: MIT Press, 2009); J. E. Harrison, Synaesthesia: Cla.s.sic and Contemporary Readings (Oxford, UK: Blackwell Publishing, 1996); A. N. Rich and J. B. Mattingley (2002), "Anomalous perception in synaesthesia: A cognitive neuroscience perspective," Nature Reviews Neuroscience 3(1): 4352; E. M. Hubbard and V. S. Ramachandran (2005), "Neurocognitive mechanisms of synesthesia," Neuron 48(3): 50920; J. Simner, C. Mulvenna, N Sagic, E. Tsakanikos, S. Witehrby, C. Fraser, K. Scott, and J. Ward (2006), "Synesthesia: The prevalence of atypical cross-modal experience," Perception 35: 102433.

Neuroscientists have identified at least fifty-four varieties of synesthesia: Caltech lecturer in computation and neural systems Melissa Saenz discovered this phenomenon quite by accident. She reported her findings, with neuroscientist Christof Koch, in the August 5, 2008, issue of Current Biology.

In mirror touch synesthesia: M. J. Banissy and J. Ward (2007), "Mirror-touch synesthesia is linked with empathy," Nature Neuroscience 10: 81516.

As for the rest of us: The bouba kiki effect was first observed by the German-American psychologist Wolfgang Kohler. W. Kohler, Gestalt Psychology (New York: Liveright, 1929).

Have you ever driven a cat crazy: B. E. Stein, M. A. Meredith, W. S. Honeycutt, and L. McDade (1989), "Behavioral indices of multisensory integration: Orientation to visual cues is affected by auditory stimuli," Journal of Cognitive Neuroscience 1: 1224.

feature integration theory: A. Treisman and G. Gelade (1980), "A feature-integration theory of attention," Cognitive Psychology 12(1): 97136.

The concept was first: P. M. Roget (1825), "Explanation of an optical deception in the appearance of the spokes of a wheel seen through vertical apertures," Philosophical Transactions of the Royal Society of London 115: 13140; S. L. Macknik (2006), "Flicker fusion," http://www.scholarpedia.org/article/Flicker_fusion.

Max Wertheimer...and Hugo Munsterberg: M. Wertheimer, Drei Abhandlungen zur Gestalttheorie (Erlangen, Germany: Philosophische Akademie, 1925); H. Munsterberg, The Photoplay: A Psychological Study (New York: D. Appelton and Co., 1916).

The dumbstruck editor sent: A. R. Luria and J. Bruner, The Mind of a Mnemonist: A Little Book About a Vast Memory (Cambridge, Ma.s.s.: Harvard University Press, 1987).

7. The Indian Rope Trick According to Teller: Teller wrote his review in the Sunday New York Times Book Review, February 13, 2005. See http://www.nytimes.com/2005/02/13/books/review/13TELLERL.html.

False memories can be devastating: E. F. Loftus, Eyewitness Testimony (Cambridge, Ma.s.s.: Harvard University Press, 1996); E. F. Loftus and J. E. Pickrell (1995), "The formation of false memories," Psychiatric Annals 25(12): 72025.

In one example: E. F. Loftus, "Made in Memory: Distortions in Memory after Misleading Communications," in G. Bower, ed., The Psychology of Learning and Motivation, vol. 30, Advances in Research and Theory (San Diego: Academic Press, 1993), 187215.

In another cla.s.sic experiment: E. F. Loftus and J. C. Palmer (1974), "Reconstruction of automobile destruction: An example of the interaction between language and memory," Journal of Verbal Learning and Verbal Behavior 13: 58589.

Nader demonstrated that: O. Hardt and K. Nader (2009), "A single standard for memory: The case for reconsolidation," Nature Reviews Neuroscience 10(3): 22434.

"Flashbulb memories": K. Nader (2003), "Memory traces unbound," Trends in Neurosciences 26(2): 6572.

In an article for Slate: Joshua Foer, "Forget Me Not," Slate.com., March 16, 2005 ( http://www.slate.com/id/2114925).

8. Expectation and a.s.sumption Theory of False Solutions: J. Tamariz, The Magic Way (Madrid, Spain: Frakson Books, 1988).

Eric Kandel: E. Kandel, In Search of Memory: The Emergence of a New Science of Mind (New York: W.W. Norton, 2007).

First, a visual region of your brain: R. A. Andersen and C. A. Buneo (2002), "Intentional maps in posterior parietal cortex," Annual Review of Neuroscience 25: 189220.

Gustav Kuhn, a psychologist and magician: Gustav Kuhn and Micahel F. Land, "There's more to magic than meets the eye," Current Biology 16(22): 95051.

If so, the neural correlate: J. A. a.s.sad and J. H. Maunsell (1995), "Neuronal correlates of inferred motion in primate posterior parietal cortex," Nature 373: 51821.

Subjects were asked to read a list of words: Study described in Blink by Malcolm Gladwell (Boston: Little, Brown, 2005).

Being reminded of their gender: Gladwell, Blink.

Half of the partic.i.p.ants in another study: "Johan C. Karremans, Wolfgang Stroebe, and Jasper Claus, "Beyond Vicary's fantasties: The impact of subliminal priming and brand choice," Journal of Experimental Social Psychology 42(6): 79298.

Advertisers use priming: J. L. Harris, J. A. Bargh, and K. D. Brownell (2009), "Priming effects of television food advertising on eating behavior," Health Psychology 28(4): 40413.

There are certainly other contributors: Most magicians wouldn't perform this particular version of the trick onstage because it's not completely fail-safe. We include it here to ill.u.s.trate priming in magic.

Signal detection theory: D. M. Green and J. A. Swets, Signal Detection Theory and Psychophysics (New York: Wiley, 1966).

Keith Payne: B. K. Payne (2001), "Prejudice and perception: The role of automatic and controlled processes in misperceiving a weapon," Journal of Personality and Social Psychology 81: 18192.

Such questions raise a deeper quandary: J. Piaget, The Origins of Intelligence in Children (New York: International University Press, 1952); J. Piaget, The Moral Judgment of the Child (London: Kegan, Paul, Trench, Trubner and Co., 1932).

Elizabeth Spelke, a developmental psychologist: E. S. Spelke (1990), "Principles of object perception," Cognitive Science 14(1): 2956.

Such research also shows that infants have: For a good review, see Laura Kotovsky and Renee Baillargeon, "The development of calibration-based reasoning about collision events in young infants," Cognition 67(3): 31151.

He notes that infants: See www.cmu.edu/cmnews/030625/03625_cognition.html.

The famous Sally-Ann test: H. Wimmer and J. Perner (1983), "Beliefs about beliefs: Representation and constraining function of wrong beliefs in young children's understanding of deception," Cognition 13: 10328.

"Adults can follow directions": J. Columbo, "Visual Attention in Infancy: Process and Product in Early Cognitive Development," in Alison Gopnik, The Philosophical Baby (New York: Farrar Straus and Giroux, 2009).

In an experiment by John Hagen: J. W. Hagen and G. H. Hale, "The Development of Attention in Children," in A. D. Pick, ed., Minnesota Symposia on Child Psychology (Minneapolis: University of Minnesota Press, 1973).

Silly Billy: D. Kaye, Seriously Silly: How to Entertain Children with Magic and Comedy (Washington, D.C.: Kaufman & Co., 2005).

9. May the Force Be with You The effect is astounding: The mathematical explanation for this trick can be found at www.numericana.com.magic.htm.

Here is Dr. Anna Berti: A. Berti, G. Bottini, M. Gandola, L. Pia, N. Smania, A. Stracciari, I. Castiglioni, G. Vallar, and E. Paulesu (2005), "Shared cortical anatomy for motor awareness and motor control," Science 309: 48891.

choice blindness: P. Johansson, L. Hall, S. Sikstrom, and A. Olsson (2005), "Failure to detect mismatches between intention and outcome in a simple decision task," Science 310: 11619.

Johansson explains that their experiments were inspired: See Richard E. Nisbett and Timothy D. Wilson (1977), "Telling more than we can know: Verbal reports on mental processes," Psychological Review 8: 23159, and http://en.wikipedia.org/wiki/introspection_illusion.

In a follow-up experiment: The studies about preferences for jam and tea and the magic questionnaire have been submitted for publication. For the latest updates, see Petter Johansson's Web site, http://www.lucs.lu.se/petter.johansson/.

Again, the results show that a majority of the partic.i.p.ants are blind: See Johansson and Hall's Web site (http://www.lucs.lu.se/projects/choiceblindness) and a YouTube video (http://www.youtube.com/watch?v=WBO03PngZPU).

Our colleagues Apollo Robbins...and...Eric Mead: See video at http://www.sfn.org/index.aspx?pagename=am2009_highlights.

In the 1970s: The original paper is B. Libet, C. A. Gleason, E. W. Wright, and D. K. Pearl (1983), "Time of conscious intention to act in relation to onset of cerebreal activity (readiness-potential)," Brain 106: 62342.

A politician in the mayor's office: See http://www.youtube.com/watch?v=-o_pYTOodu4.

John-Dylan Haynes: C. S. Soon, M. Bra.s.s, H. J. Heinze, and J. D. Haynes (2008), "Unconscious determinants of free decisions in the human brain," Nature Neuroscience 11(5): 54345.