Neurophilosophy

A novel temporal illusion, in which the cause of an event is perceived to occur after the event itself, provides some insight into the brain mechanisms underlying conscious perception. The illusion, described in the journal Current Biology by a team of researchers from France, suggests that the unconscious representation of a visual object is processed for around one tenth of a second before it enters conscious awareness.

Chien-Te Wu and his colleagues at the Brain and Cognition Research Centre in Toulouse used a visual phenomenon called motion-induced blindness, in which a constantly rotating background causes prominent and motionless visual stimuli to disappear and reappear, as demonstrated in the video below. Fixate on the flashing green spot in the centre, and you’ll notice that the surrounding yellow spots begin to disappear and reappear after about ten seconds. Then replay the clip and focus on any of the yellow spots; you’ll see that it is a visual disappearance illusion. Exactly how it works is unclear; according to one hypothesis it is due to the properties of neurons in area V1 of the visual cortex.




The researchers first used a variation of these stimuli to test the occurence and duration of the motion-induced blindness effect. In these pre-test trials, seven participants were presented with a static yellow ring on a rotating background, and asked to report when the ring disappeared from and reappeared to conscious awareness, by respectively pressing and releasing a button. This was repeated 200 times for each participant, and the reported durations in all trials – between a few hundred milliseconds and several seconds – were plotted onto a graph. The data from each participant were then divided into four equal sets, and the average of the lowest 25% was calculated, to give a value called PreQ25.

In the test trials, a dot was flashed for 50 milliseconds in the location of the ring after it was perceived to disappear. For each participant, this was timed so that the dot appeared at the exact time delay given by the PreQ25 value in the previous trials. In 75% of the trials, the dot was perceived to appear before the reappearance of the ring. As expected, it hastened the perceived reappearance of the ring, as revealed by second graph plotting motion-induced blindness duration. In the remaining trials, the ring should have been perceived to reappear before the dot was flashed. However, the participants reported seeing the ring before the dot in around 90% of trials. Evidently, the perceived time sequence of events had been reversed – the participants reported seeing the cause (the dot) after the effect (the reappearance of the ring).

How might this be explained? One possibility is that the duration of motion-induced blindness was shorter in the test than in the pre-test trials. But further measurements of the duration, carried out during  post-test trials, showed that it had not changed significantly across the trials. Another possible explanation is that the flashed dots were also rendered invisible by the illusion, as it was presented in the same location as the ring, but a second experiment ruled this out. The participants were presented with two rings on opposite sides of the roating background. A dot was flashed in the centre of each, half a second after the onset of the illusion, and they were asked to state the order in which they perceived the dots to appear. This was then repeated on a static background. The reported order was the same in both conditions, showing that the illusion had no effect on the perception of the dots. 

Wu and his colleagues therefore conclude that the unconscious representation of the ring is perceived with a shorter time delay than the flashed dot. That is, because the visual system contained a representation of the ring before it was rendered invisible, it could reactivated quickly and fast-tracked into conscious awareness when it was perceived to reappear. The flashed dot, on the other hand, was a completely novel stimulus, so took longer to enter the stream of consciousness. 

The researchers then carried out another experiment designed to measure the time difference between processing in the conscious and unconsious streams. They repeated the first experiment, but this time introduced a subtle change in the colour of the ring, which occurred at various times relative to the flashed dot. After each trial, the participants reported whether they perceived the ring or the dot first, and were also asked what colour the ring was when it first reappeared. By plotting colour choice against the time of the colour change, the researchers could calculate exactly when the unconscious representation of the ring entered into conscious awareness.

This revealed that the colour change needed to occur about one tenth of a second before the flashing dot in order for the ring and the dot to be perceived as appearing simultaneously. In other words, after the flashed dot induced perception of the ring, the first ring colour that the participants tended to perceive was the colour that the ring had been about 100 milliseconds before the dot appeared, rather than the colour it was at the time the dot was flashed.

Finally, the researchers investigated whether the time illusion could be induced by a time mismatch between the conscious and unconscious representations of the same object, rather than by differences in the time at which two different objects appear. To do so, they modified the last experiment, and introduced a prominent change in the colour of the ring. Here, the dot was not flashed – instead, the colour change occured while the ring was perceptually suppressed, and triggered the ring’s early reappearance. The participants were required to state which the colour the ring was when it first reappeared into their awareness. Remarkably, the colour most often reported was the old one, even though it was the change to the new colour that triggered the reappearance of the ring. So although the new colour was registered unconsciously by the visual system, it was the old colour that was perceived when the ring reappeared. 

Related:


Wu, C.-T., et al (2009). The Temporal Interplay between Conscious and Unconscious Perceptual Streams. Curr. Biol. DOI: 10.1016/j.cub.2009.10.017.

Comments

  1. #1 Rene Najera
    November 6, 2009

    Wow! The way the mind works is really wild. Thanks for this posting.

  2. #2 jj
    November 6, 2009

    Crazy! I find that when the yellow dots disappear, and I notice it, that my eyes seem to re-scan (I can feel it!) and they pop back up. The harder I try to concentrate on the blinking green dot, the longer the yellow disappear for. But it’s hard!

  3. #3 Adrian Morgan
    November 6, 2009

    The illusion in the video reminds me somewhat of the illusion that Jack Pettigrew associated with hemispheric rivalry, as in this television report (which no longer contains video, only transcript and links). I don’t know what the current consensus is about that, but I certainly found it interesting at the time.

  4. #4 Benchtop
    November 7, 2009

    Sounds like perceptual frame-snapping.
    I have seen wheel spokes appear to reverse rotation when they get aroune 10 rpm – in broad daylight – not stroboscopic.

  5. #5 Benjamin Nelson
    November 7, 2009

    Fascinating.

    (This may be a naive idea of what’s going on, or maybe it’s just rephrasing what you’ve said in other terms. If so, then apologies.) But surely the illusion in the first video must involve a story featuring at least two things. a) We know that there are fewer color receptors at the periphery of the eye (which would explain why the illusion is more effective when you’re closer to the picture and the picture is enlarged). b) The receptors are color-sensitive, so perhaps the perception of yellow is “crowded out” by the blue background.

    (Granted, that wouldn’t be enough of a story, because we also need to explain why movement matters. I guess then memory must play a role, perhaps in the way you so clearly explained later in the post.)

    Leading up to my question: would the same effect happen if the background matrix were a different color?

  6. #6 Dan
    November 8, 2009

    I think this may help you to understand;

    Years ago,after leaving the armed services, I was abducted by Grays that are working for “the Federation”.
    The Federation is “a NATO type organization”, of Grays,
    Reptilian, Moth men,(all non human types about 42 different beings mostly violent military males ) different recessive beings too, that are discussed in various
    contact books, and thousands of internet sites for the smart people to learn and study.
    I was taken to the Federation by physical, barely visible in our spectrum.. I used infrared/spectrum lenses goggles,to see them
    race of sub space beings. Regressive Beings working with Grays, called the White Brotherhood. After my negative experiances
    of many years I learned from the Grays themselves ,(they abducted me for sperm, surgical removal, as they do with womens eggs all around the world),
    This is what I know to be true: 1. all extraterrestrials are physical carbon based,
    silicon based, or molecular based beings,including the ones who use magnetic field tecnology to cloak themselves, travel or
    appear as a humans, i.e. stable plasmon technology. These technologies can be detected with geiger counters,
    and magnetic field detectors sold “on line”, directional is preferred….find the electrical devices on them,and around them in their nearby craft.
    For your homes and cars..some of the Gray and reptilian devices can be disrupted by Mhz frequency devices built at home,
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    races of sub space
    beings have technology that I have seen, are defended against with hand lasers, built at home!!
    2.Critical, we are not the only humans in the universe or multiverse…there are humans from Lyra, Pleadians,
    Andromidan, Cassiopeian, Simion and billions more! 3, Even more important the Gray Federation is using Religion to “Dumb Down”,
    all of us on earth. 3. All Religions are false, there is no god, only Extraterrestrials and human support groups from other
    worlds, the earths which NASA is just now locating are inhabited.

    Our military is being attacked by the Grays ,(google on the internet), and
    Reptilian Federation all the time, all the time, The shootings at Army bases world wide are mind controlled by the Gray Federation,
    as is the sweat lodge incident , 911, and the current state of our economy and health…chem trails,
    ( 8-120 MHZ broadband mind control technologies piggybacked on T.V. cell phone and cable, important for you to remember).
    A strategy used by the Grays and others is to mind control in the name of Religions, a not so well informed
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    those of us who understand Gray, Reptilian Military mind control Strategy and Tactics( for example…
    Jesus is my mentor and I
    am speaking with him now, no!! Jesus is dead It was told to me Jesus did exist , but he is dead it’s an ET who learned earth languages.!!!!!!!!!!!!!!!!!!!!!!)
    It is not Obamas fault,
    nor is it Hilliary Clintons fault…it was not President Kennedy fault, but the Gray military Federation did kill him in part
    because the Grays and others did not want us in Space.

    It’s being done mainly because these other types of ET”s, Grays, reptilian Snake beings, insectoid which are more technically advanced
    and regressive in the way they think and act are working together against humans, abducting women for there experiments etc.

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    shielding material also works in many labs with high emf use.
    at home depot, particle dectors magnetic particle detectors…Critical infrared binoculars,
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    Have extra food at home for your family, it is no coincidence that in the movies on
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    maybe another war? The humans from hollywood, like me are trying to through this note, and films to
    inform you of the risks we are in! 2012, alien mind control, H1N1 gray federation attacks on humans.

    The Gray Federation ruined myself and family like they did with Alex collier, and Billy Meir, Michael Salla and others… I know about the
    Photon belt we are entering please look it up on the internet…many friendly human races are trying to help us now
    When I was at the Gray army here in Santa FE, N.M.base, I did see many things, I have a PhD, I’M a quick learner and
    can now read their sumerian type alphabet and words… I was taken on one type of craft they use, how they fly and what they use in them…the saucer
    shaped craft use electrical batteries as propulsion power, in the middle of some saucers there is a large circular ceiling to floor
    barrel structure it contains lithium type batteries extremely high voltage charges. The craft are made of layered and compressed metals titanium compounds,
    the outer skin is electrified to reduce and eliminate drag and atmospheric resistance. Inside the saucer is a network of Compressed
    frequency transmitting fiber optics for controls and for ON BOARD GUIDENCE SYSTEMS, SIMPLE. THEY USE THE EARTHS MAGNETIC AND GRAVATATIONAL FIELDS TO FLY.
    THE COPPER CLINDER CIRCLES ON TOP OF THE CRAFT AND BOTTOM SPIN, PICTURE TWO SMALLER CIRCULAR DISKS ON TOP AND BOTTOM
    SPINING INDEPENDENTLY OF THE SAUCER. THEY CHARGE UP..THAT DIFFERENTIAL OF CHARGES INTERACTS
    WITH A PLANETS OR SPACES MAGNETIC FIELDS FOR LIFT AND MOVEMENT. THE SAUCERS ARE SHIELDED TO PREVENT EXPLOSIONS AND TO PREVENT
    MAGNETIC FIELD INTERACTIVITY……(THE OUTER SHELL IS CHARGED UP TO FLY W/O RESEISTANCE, IT STINGS when touched electrical pulse).
    …I’M NOT A PHYSICS MAJOR BUT DID STUDY SOME ENGENERING.

    They are trying to mind control our socities through Mhz frequency control, we think in about 11-80 Mhz,
    and they use computers and oscilloscope combo. type MRI type equipment to read thoughts as we read print or a scientist reads peaks on a
    graph, as well as gravitational field tech. to beam in false info.
    Shield your brains and spinal cords!!!
    All of our military and armed forces should wear velostat (signal protection electrical grounded materials on your head)
    caps and monitor the frequency changes around them, the
    government of the USA ours, needs to be informed of the grays methods and take steps to help each other, protect our
    families people this is real….(people in Britian were not ready, prepared for WWII, Study military history )
    …(we have a very weak and complacent military/police/NSA/CIA/) The Grays have even infiltrated some gov’t individuals
    in these agencies…………………..!!! Just because you were in church on sunday and you see people speaking in tongs,
    falling to the floor, and saying they are talking to god? there is no god only ET groups, ET governments.

    Love
    Dan

    P.S. This was written under partial duress……they know where I live. Pass the info on.

    The Federated reptilian/gray/insectoid societies are using harmful
    technology to harm the human mind, causing
    memory loss and fatigue…FIGHT BACK, I use the above mentioned technology
    and when I go out and they start to harm my body with high intensity back spasm devices
    i.e. microwave, particle , mind control. I use my mind and picture each attacker
    being attacked by me. They hate loud music, food odors, perfumes, light, and our
    minds killing them…! I keep a gun and tazer by my side always now!!!

    Listen to this highly educated old man, if you see a craft these are not dolls, these are recessive
    violent, harmful, controlling alien males..read the info on the net with a grain of salt,
    why haven’t they come forward? They wont because of violent abductions, use logic.
    Protect your brains!!! stay away from them, Betty and Barney Hill were assaulted,
    all of the abduction cases are harmful rape and kidnapping humans, we in the USA have laws
    against these crimes yet our government turns in another direction. Because they control some
    people in our not one world gov’t yet.

    Space is alot more crowded than most people know, extremely dangerous NASA knows..Our Rocket
    systems and defense systems are frail…

    Connect the dots………biology, secrect governments, mind control, abductions,
    alien tecnologies genetic and magnetic, and we wonder where
    they come from reverse designs from crashed UFO…s

  7. #7 Bjorn Westergard
    November 8, 2009

    “it could reactivated quickly and fast-tracked into conscious awareness when it was perceived to reappear”

    What does it mean for something to come “into” consciousness? Doesn’t this ascribe some unity to consciousness? On what basis? Why should there be a sharp dividing line between activity in the brain that is related to conscious versus unconscious phenomena?

    http://en.wikipedia.org/wiki/Multiple_Drafts_Model

  8. #8 David
    November 8, 2009

    Here’s a very interesting 44 min. talk by Prof. Meister from Harvard that he gave at the place where I work a few days back on the subject of visual perception and some amazing stuff that the neurons in the retina do.

    Unfortunately the demos are not visible due to the way the talk was recorded.

  9. #9 Jon
    November 22, 2009

    “In the remaining trials, the ring should have been perceived to reappear before the dot was flashed. However, the participants reported seeing the ring before the dot in around 90% of trials.”

    Doesn’t this mean they saw what was predicted 90% of the time, in contradiction to your conclusion:

    “Evidently, the perceived time sequence of events had been reversed – the participants reported seeing the cause (the dot) after the effect (the reappearance of the ring).”

  10. #10 Crazy Mermaid
    January 24, 2010

    Fascinating as usual.

  11. #11 tresho
    February 7, 2010

    I’ve been aware of this for some years now, and this article gave me a name for it. I believe this phenomenon can account for some motor vehicle accidents, where a driver fails to see a significant object along his way due to distraction of other moving objects in his visual field, or due to flashing lights along the road. The giant LED movie screens now being erected along major highways may thus have some unfortunate consequences for the traveling public.

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