POSTDICTION AND THE BRAIN.

Burkhard Bilger’s article on David Eagleman in the April 25 New Yorker is one of the most interesting things I’ve read in a long time; I haven’t even finished it yet, but I had to post a passage from page 59 that provides a nice use of the word postdiction (see this LH post from a year ago) and a linguistic example. Eagleman studies our sense of time and how the brain creates it:

Like Crick, Eagleman was fascinated by consciousness. He thought of time not just as a neuronal computation—a matter for biological clocks—but as a window on the movements of the mind. In a paper published in Science in 2000, for instance, Eagleman looked at an optical illusion known as the flash-lag effect. The illusion could take many forms, but in Eagleman’s version it consisted of a white dot flashing on a screen as a green circle passed over it. To determine where the dot hit the circle, Eagleman found, his subjects’ minds had to travel back and forth in time. They saw the dot flash, then watched the circle move and calculated its trajectory, then went back and placed the dot on the circle. It wasn’t a matter of prediction, he wrote, but of postdiction.
Something similar happens in language all the time, Dean Buonomano told me. If someone says, “The mouse on the desk is broken,” your mind calls forth a different image than if you hear, “The mouse on the desk is eating cheese.” Your brain registers the word “mouse,” waits for its context, and only then goes back to visualize it. But language leaves time for second thoughts. The flash-lag effect seems instantaneous. It’s as if the word “mouse” were changed to “track pad” before you even heard it.

The article is wonderfully written (“The most recent neuroscience papers make the brain sound like a Victorian attic, full of odd, vaguely labelled objects ticking away in every corner”), and you won’t regret devoting a chunk of your day to reading it.

Comments

  1. “odd, vaguely labelled objects ticking away in every corner”: were Victorian attics full of clockwork devices that someone wound up regularly? No wonder then that every Victorian family needed to have a mad aunt confined in the attic.

  2. John J Emerson says:

    Clocks offer at best a convenient fiction, he says. They imply that time ticks steadily, predictably forward, when our experience shows that it often does the opposite: it stretches and compresses, skips a beat and doubles back.
    This strikes me as careless writing at best. He’s talking about our mind’s processing of time. Clocks are pretty much accurate about physical events. Various people experiencing the event would experience it in various ways, depending on their degree of concern with the event.
    I haven’t read much Heidegger or Bergson, but it’s my impression that they confuse the issue in exactly this way.
    None of what I say is true inside philosophy classrooms, of course.

  3. What is the mechanism if the brain can’t “wait for [a word's] context” within a sentence? Example: “I need to buy a new mouse.”

  4. This might have some relation to the idea of “Baroque sentences” as I’ve blogged about in relation to reading Saramago — it takes long enough to read one of his long sentences, to get the context necessary for understanding its phrases and fitting them together, to overwhelm the normal neural lag for collecting context.

  5. What is the mechanism if the brain can’t “wait for [a word's] context” within a sentence? Example: “I need to buy a new mouse.”
    The mechanism is to ask the speaker what is meant. “Brains” do not serve that only stand and wait.

  6. JE: I haven’t read much Heidegger or Bergson, but it’s my impression that they confuse the issue in exactly this way.
    I waited for postdiction to cut in, hoping to understand that, but nothing happened – so I have to ask. What “issue” do you mean ? “Time” ? “Measurement of time” ? “Perception of time” ?
    Are you perfectly clear as to what is involved in the perception and measurement of time, without more ado ? You seem to be saying: “I refute Bergson thus (consults watch)”.

  7. John J Emerson says:

    Making it seem that the peculiarities of our perception of time tell us about the time of the events that we happen to experience, rather than being an aspect of human consciousness.
    For example, in the article the interviewee described his own experience of falling off a roof, and the slowing down of his time perception. Supposing his mother had been watching, she also would have had a similar but not identical kind of altered experience. A random unrelated person might have still a third experience, a fourth person who thought that it was a bag of trash falling a fourth experience, and someone watching with a stopwatch a fifth experience. But the time of the falling was the same.
    I’m not sure, but suspect, that Bergson and Heidegger were idealists of some sort who perhaps believed that subjective time is the only time, or that they privilege subjectivity over objectivity in some way, but why do that?

  8. the time of falling was the same
    Eagleman talks about this some in the article, during the portion where he is having volunteers fall from great heights while looking at a stopwatch.

  9. (oh also, this is kind of unrelated, but if the young Eagleman had been falling at near the speed of light, the duration of his fall would in fact be different when measured from his reference frame than from his mother’s.)

  10. Quantum physics and relativity have long been the most effective tools for confusing issues, though chaos is closing fast.

  11. Quantum physics and relativity have long been the most effective tools for confusing issues, though chaos is closing fast.
    John, special relativity correctly describes certain phenomena of the world in motion, as verified by measurement. Shitkicking realism doesn’t correctly describe them. There’s nothing confusing about that. It just means that intuition is non-intuitive, and needs training.

  12. dearieme says:

    That’s interesting, John. I’ve long thought that everyman’s versions of Relativity and Quantum Mechanics were on a par with astrology, but also thought that Chaos was better grasped. Oh well, back to waiting to find a political writer who can distinguish an inflection from a turning point.

  13. dearieme says:

    And let’s not overlook the Second Law.

  14. J. W. Brewer says:

    Heidegger/Bergson are latecomers to a very long-running sense of bafflement. Perhaps the locus classicus is from St. Augustine of Hippo (the Grumbly Stu of 4th/5th century North Africa?): “For what is time? Who can easily and briefly explain it? Who even in thought can comprehend it, even to the pronouncing of a word concerning it? But what in speaking do we refer to more familiarly and knowingly than time? And certainly we understand when we speak of it; we understand also when we hear it spoken of by another. What, then, is time? If no one ask of me, I know; if I wish to explain to him who asks, I know not.” – from book XI of the Confessions, tr. A.C. Outler.

  15. Relativity, Quantum Mechanics and Chaos are not needed down on the farm. But many of the electronic instruments that you may use there, such as a computer database for keeping track of the cows, were built by people who had to understand related matters in order to build the instruments.
    A doctor knows things about your body that you don’t. Why should it be a problem that physicists know things about the world that you don’t ? It is probably the sociological and political aspects of such division of knowledge that are bugging you.

  16. What, then, is time? If no one ask of me, I know; if I wish to explain to him who asks, I know not.
    J.W., Augustine was an anti-Grumbly in that respect. My actual tendency is more robust: when nobody asks me, I don’t know nuttin’. When somebody asks me to explain something to them, then I suddenly know all about it.
    Kleist called it die allmähliche Verfertigung der Gedanken beim Reden.

  17. Relatively, quantum physics, and chaos are all, as far as I’m concerned, true. But they still are useful for causing confusion with.

  18. “Relativity….”

  19. Ah, then we are in 100% agreement.

  20. This strikes me as careless writing at best.
    You’re not complaining about the writing, you’re complaining about the thinking of the guy he’s writing about. Unless, like Grumbly, you’re complaining about everything.

  21. At best it’s careless writing by a journalist who’s paraphrasing a scientist. At worst, he’s accurately paraphrasing the scientist.
    Based on the ending of the article, he may indeed be the kind of visionary scientist who extrapolates wildly from his results and believes that that personal experience of his was a change in time itself rather than a changed experience of time.

  22. JE: a change in time itself rather than a changed experience of time
    “Time itself” is a metaphysical notion. You cannot consistently appeal to such a notion while claiming that “relativity, quantum physics, and chaos are all, as far as I’m concerned, true”.
    In presenting your thought experiment above – involving the interview, his mother, a random unrelated person, and a fourth and fifth person – you have not taken into account the crucial sixth person: you yourself, in whose imagination all the events are “objective” ones, as if in a theater not of this world, and not affected by the physics of this world.
    The crux of special relativity is that the existence of such a universal, detached observer is inconsistent with the way the world is measured to be. Why don’t you just accept it, and move on from there ? What is hindering you ?

  23. They did an experiment on relativity, and it worked. Two extremely accurate clocks were set to the same time. One was put on a satellite and circled the globe thousands of time, and after millions of miles it returned to earth. And lo! there was a time difference of a fraction of a second between the two clocks.
    This has nothing to do with how long someone falling off the roof takes to hit. What I’m saying is interpersonal differences in perception of time have nothing in particular to do with relativity. (If it were a relativistic difference, it would be objectifiable with clocks, as in the experiment, and not subjective).
    Between my metaphysical notion and your relativized metaphysical notion, I’ll take mine.

  24. There are people who can’t understand how there could have been debates over centuries about whether the earth or the sun was at the center of the universe. They think: “boy, those guys must have been pretty stupid”, or “it was all due to stubborn priests who tried to suppress the truth”.
    But look at the difficulties many people nowadays still have understanding that the notion of an objective observer just doesn’t fit what is observed to happen in the world. “Paradigm shifts” are non-trivial, and hard to get a handle on.

  25. A doctor knows things about your body that you don’t. Why should it be a problem that physicists know things about the world that you don’t ? It is probably the sociological and political aspects of such division of knowledge that are bugging you.
    So I suppose a sociologist understands what’s bugging me better than I do. That just bugs me.

  26. Grumbly, relativity has nothing to do with whether or not the guy’s peak experience falling off a roof taught him something about how fast he was falling. The difference between various experiences of the same event tells us about the ways the brain processes events in time.
    There’s a lot of selection bias in the talk about great scientific geniuses whose ideas were rejected. During that same era there were thousands of great scientific geniuses whose discoveries were quite rightly rejected, because they were wrong. But their names have been forgotten, with the exception of a few of the most famous such as Paracelsus and Charles Fourier.

  27. This has nothing to do with how long someone falling off the roof takes to hit. What I’m saying is interpersonal differences in perception of time have nothing in particular to do with relativity. (If it were a relativistic difference, it would be objectifiable with clocks, as in the experiment, and not subjective).
    It has nothing particular to do with relativity, but there is a general point in common. When you forbid measurement, every evaluation of subjective experience is a subjective one. When you allow measurement, every measurement of subjective experience is still measurement by a subject, namely the measuring scientist.
    His evaluation is the additional point of view of an additional subject. It does not “invalidate” the subjective experiences of the subjects, nor “take precedence over” them. Scientific measurements are intended to be reproducible by others. But that requires laboratory conditions: the special conditions of special subjects, i.e. scientists. If we lived in laboratory conditions, that might seem to make life much simpler – but who would be running the laboratory ?
    In any case, sexual reproduction does not require laboratory conditions, nor does it have to be reproducible by others, though it often is.

  28. Measurement of the speed of falling bodies can be, and is, mechanized, so that no mind enters into the measurement. Things which are not experienced by minds do not become less real.
    I do give pride of place to the physical measurement over the subjective experience. To me that’s what “falling” means, a measurable physical movement of an object. This does not invalidate the guy’s experience of falling, as long as he doesn’t interpret it to mean that the elapsed time was different than would have been measured.

  29. It’s odd that the article doesn’t mention the anecdote about Einstein and the roofer who fell off his roof. It supposedly relates the circumstances in which Einstein got the idea that an observational frame observed to be “falling” in a gravitational field seems to be motionless within that frame. I encountered it, or part of it, in an essay by Hans Blumenberg:

    Als Einstein gefragt wurde, wie er auf die Ausschaltung des Kraftbegriffs aus der Beschreibung der Gravitation, also der Schwerkraft oder der Anziehnungskraft von Massen, in der Allgemeinen Relativitätstheorie gekommen sei, erzählte er die Geschichte vom Dachdecker. Der sei zufällig in Berlin vor seinen Augen vom Dach gestürzt, aber so glücklich gefallen, daß er überlebte und sogleich vom herzueilenden Einstein befragt werden konnte. Kern seiner Auskunft war, daß er von Schwerkraft nichts bemerkt habe. [Blumenberg, "Der unvermeidliche Rückgang aufs Anthropomorphe", in Die Vollzähligkeit der Sterne, 1997, Suhrkamp TB (2000)]

    Here is a slightly more explicit presentation that makes the anecdote sound like a posthumous one. There must be more about this in English, but all I found was from a New York Times article from 1919. It’s on page “2152″ in a 100%-rant PDF entitled The manufacture and sale of Saint Einstein at “jewishracism.com”, for God’s sake. Because the PDF is Acrobat-”protected”, I can’t copy the newspaper excerpt.

  30. The philosophy in this article is absolutely attrocious. The brain is like Kublai Khan in his place? Then what is it that’s like Kublai Khan’s brain!? This is analogy making basics 101: don’t explain something using another thing that’s a less well understood version of the same thing!
    I wrote a blog post to this effect: blog.carlsensei dot com/post/4782335802

  31. To me, the most remarkable thing is that this man was falling down at the speed of light.
    Last week, I went to the London Zoo. There were no hippos, they’ve been relocated out of town. Plenty of giraffes, though.

  32. You’re so cute, Crown – doing your Madeleine Bassett number in order to make everybody be nice to each other !

  33. Here is that excerpt from the 1919 NYT article, copied manually. I have reproduced the typographical curiosities of the excerpt as they appear in the astonishingly obsessive, rabid 2825-page “treatise” on “Saint Einstein” that I mentioned above:

    Inspired as Newton was [,] but by the fall of a man from a roof instead of the fall of apple. [***] The doctor lives on the top floor of a fashionable apartment house on one of the few elevated spots in Berlin–so to say, close to the stars which he studies, not with a telescope, but rather with the mental eye, and so far only as they come within the range of his mathematical formulae; for he is not an astronomer but a physicist.
        It was from his lofty library, in which this conservation took place, that he observed years ago a man dropping from a neighboring roof–luckily on a pile of soft rubbish–and escaping almost without injury. This man told Dr. Einstein that in falling he experienced no sensation commonly considered as the effect of gravity, which, according to Newton’s theory, would pull him down violently toward the earth. This incident, followed by further researches along the same line, started in his mind a complicated chain of thoughts leading finally, as he expressed it, ‘not to a disavowal of Newton’s theory of gravitation, but to a sublimation of supplement of it. [***] It was during the development of the formulas for difform motions that the incident of the man falling from the roof gave me the idea that gravitation might be explained by difform motion.’

  34. It’s not so much a number, more that I have little to add about Einstein, Bergson and the rest, but I still want to get in my two-cents worth of comment.
    Not changing the subject at all, still talking of the New Yorker, my most recent copy had an article about Theodor Fontane, who was made to sound very sympathetic. Is this someone you like to read, Grumbly? Effi Briest? They (whoever it was) said there weren’t many English translations until recently.

  35. I certainly do like Fontane. Just this month I read L’Adultera [The Woman Taken in Adultery], and soon I will start Mathilde Möhring. Save your tuppence to buy a copy of Effi Briest, by all means.
    For all that I have read, I am again and again amazed at the subtlety and “modernity” of what certain French and German novelists wrote in the 18th-19th centuries. For instance Constant’s Adolphe (1816), which I read last week.
    But I musn’t gush, as you have told me.

  36. mustn’t …

  37. Wow, thanks for the Einstein ref., Stu. And always nice to see Blumenberg mentioned.

  38. Thanks, Jeremy. It hadn’t occurred to me to search in the NYT archives – duh. Does one have to have a subscription ?

  39. Thanks. I shall impose a tax until I can afford to buy a copy of F. E. Briest.

  40. “Jeremy”, how confusing.

  41. I’m not sure if one needs a subscription. I have one and can access the file… If you have trouble let me know and I’ll e-mail it to you.

  42. “Jeremy”, how confusing
    Well, selbst schuld for gadding about in rainbow nicks. Even your own mother could be forgiven if she forgot your real name. But that’s showbiz.

  43. Maybe I am a bit late to this conversation, but as someone who has actually read Eagleman’s research, I can say with some certainty that he is interested in how *individual perception* of time changes due to psychological (rather than relativistic) factors, and not at all interested in how mechanical or objective measurements of time change (if any can be said to exist). It is the writer of the article who confused the two.

  44. bruessel says:

    AJP, for classical literature, Project Gutenberg i.e. gutenberg.org is your friend.

  45. Thank you, Bruessel. I always forget Project Gutenberg exists. Now I’ve read some pages of Effi Briest there I think I’ll buy it. I like actual books if I have the choice, and the English translation seems a bit old fashioned and dusty – though perhaps the original is too.

  46. Here, by the way, is the New Yorker article about Fontane.

  47. gobodonry says:

    Im 19 going on 20 in may i got my nose done at exposed dawgs and it hurting really unhealthy and its been 5 to 6 weeks the inside of my nose is sollowen and its starting 2 puss is that a well-disposed trend and when i asked the task i got it done they said nothing was disgraceful with it and my playmate got hers done 2 days in advance my and she isnt having any trouble nor pussing so how do i remember if i dont make to worry about if my nose is infected or no [spam url deleted—LH]

  48. This spam is surreal.

  49. Crown, I do hope you find translations of Fontane that are not “a bit old fashioned and dusty”, as indeed that one is of Effi Briest to which you linked. Daniel Mendelsohn, who wrote that New Yorker article, must be confusing Fontane with some other writer, or has read Fontane only in incompetent translations.
    I can find no other explanations for the opinion he gives near the beginning of the piece:

    Compensating by narrative skill for the lack of visible interest is an excellent way to sum up both the strangeness and the beauty of Fontane’s fiction. The topography of his plots is admittedly as flat and monotonous as the notoriously bland landscape of his Prussian homeland, Brandenburg (about which he lovingly wrote in a multivolume work).

    This is unrecycleable rubbish, as anyone can verify for themselves by reading anything of Fontane. Even though I in principle have zero interest in the “topography” of novels (avenues of lime trees etc in Austen and Trollope, for instance), I have retained vivid, detailed images of the countrysides, city streets, buildings and their interior furnishings as described in Effi Briest, L’Adultera, Irrungen Wirrungen and Der Stechlin – especially Der Stechlin.
    I would set Fontane’s descriptive powers next to those of Gaskell in North and South, or Hardy in Tess. I encourage you to buy one of Fontane’s novels and make up your own mind.

  50. To get a small idea of how the Stechlin lake area was 150 years ago, as described by Fontane in Der Stechlin, look at this website. The area appears to be now overrun by tourism.

  51. Thanks for that opinion, Stu. I looked at a more recent translation but I can’t say I liked it much better, it’s more up-to-date (“canna lilies” instead of “Indian shot”, for instance) but it’s harder to understand. I suppose it’s my only option, though. I tried reading the German but it’s like listening to someone talk while I’ve got wads of cotton wool in my ears, I just can’t hear any nuance.
    It’s a lovely spot, that Stechlin – Roofensee. A bit dangerous nowadays, with the parachutists. If it’s on the border of Mecklenburg, I heard a lot about that countryside from my Gräfin, who grew up around there.

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