1 / 93

The Varieties of Conscious Seeing Andy Clark

The Varieties of Conscious Seeing Andy Clark School of Philosophy, Psychology and Language Sciences (PPLS) University of Edinburgh, Scotland, UK andy.clark@ed.ac.uk. Thanks.

Télécharger la présentation

The Varieties of Conscious Seeing Andy Clark

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. The Varieties of Conscious Seeing Andy Clark School of Philosophy, Psychology and Language Sciences (PPLS) University of Edinburgh, Scotland, UK andy.clark@ed.ac.uk

  2. Thanks. Thanks to Julian Kiverstein, Rob McIntosh, Matthew Nudds, Tillmann Vierkant and the participants in the Edinburgh University PPIG (Philosophy, Psychology and Informatics Reading Group) for stimulating discussion of some of these issues. This talk was prepared thanks to support from the AHRC, under the ESF Eurocores CNCC scheme, for the CONTACT (Consciousness in Interaction) project, AH/E511139/1.

  3. Conscious Visual Experience. What is conscious visual experience? How can we tell what figures in conscious visual experience? (It’s harder than it looks since asking people is not good enough) Is conscious visual experience all of one basic type, or are there varieties of conscious seeing? Is there some kind of information-processing profile that is both distinctive of, and perhaps helps explain, conscious visual experience itself?

  4. Strategy: Look at two familiar bodies of evidence that seem to bear on the nature and extent of conscious visual experience. Change Blindness Visual Form Agnosia ….while asking lots of difficult questions ..then offer a positive suggestion.

  5. A General Issue to Pursue Might we often beconfusing the contents of visual experience with something much more narrow, such as the contents of noticed (Dretske (2006)), conceptualized(Wallhagen (2007)), or world-describing (Jeannerod (2007)), Nudds (ms)), visual experience?? See also Block (2007). Call this the ‘Narrow Vision of Conscious Vision Worry’

  6. Change Blindness (Again) Seeing and Noticing Visual Form Agnosia (Again) Two Types of Conscious Visual Content? A Positive Story

  7. What should we conclude from these kinds of demos? • A popular early suggestion (Dennett (1969) (1991), Ballard (1991), O’Regan (1992), Churchland et al (1994), Clark (1997)): • Minimal internal representation: you don’t notice the difference because your brain never created a ‘rich internal representation’ of the scene in the first place. • Rather, we make do with partial (perhaps ‘gist’-oriented) internal encodings and a capacity for rapid information-accessing saccades.

  8. Problem: it now seems that the internal representations are not so minimal after all….

  9. Evidence for persisting, and not especially sparse, representations of the pre-change stimulus. Hollingworth and Henderson (2002) show that as long as a target object is fixated (i.e. directly targeted by foveated vision) and attended both before and after the change, subjects are able to detect and report even quite small and subtle alterations, such as the change of one telephone to another. (See also Simons et al (2002)) + even when the change is not explicitly noticed, evidence of covert awareness. Hollingworth et al (op cit) showed that fixation duration on the changed object (post-change) was longer than under normal (no change) conditions Silverman and Mack (2001) showed priming effects for 'unnoticed' changes.

  10. A Good Question: If we have these rich(er) int reps, why don’t we always notice the changes? Simons et al suggest we fail to compare the pre- and post- change representations. But that merely pushes the question back a step. Why don’t we? Suggestion: what is at work here is a very general principle of operation of the embodied, situated, human nervous system, that I call “motor deference”. (Clark (forthcoming), Ferreira, Apel and Henderson (submitted)) We tend to prefer to use a motor routine to fetch information from the scene in front of us, even if we command a perfectly good stored representation.

  11. Why Defer? • Ferreira, Apel and Henderson (submitted)) • Safe…perhaps more reliable than memory. • Lessens the moment-by-moment load on internal working memory: just fetches what is needed when it is needed.

  12. But one question still unanswered: How much of the detail that we moment-by-moment encode, and that is sometimes demonstrably preserved even when we don’t notice changes to those very elements in the scene, makes it (at the time of exposure) into conscious visual awareness? Concretely: In typical CB experiments, do you consciously visually experience the very items whose changed appearance you, later failed to notice?

  13. Change Blindness (Again) Seeing and Noticing Visual Form Agnosia (Again) Two Types of Conscious Visual Content? A Positive Story

  14. Fig courtesy of Jeroen Smeets

  15. According to Wallhagen (2007) this clever manipulation merely reveals (allows us to notice) what was already present to visual experience even in the standard unaugmented Müller-Lyer. It is just that in the standard case we do not noticethat our own conscious perception has both the veridical and the non-verdical content too (ie there are multiple inconsistent contents given in conscious visual experience)

  16. Similar line in Cara Spencer, re Ebbinghaus illusion (2007, p.315, my emphasis): Maybe we correctly represent each disc size in experience but “the distorting effect of the illusion partly serves to draw the attention away from certain features of the experience, such as its representation of each individual disc, so that the subject does not notice how they compare’.

  17. These moves require a kind of division of the agent into what might be termed the bareexperiencing agent and the noticing agent. On this model the bare experiencing agent is fully consciously aware of much that the noticing agent misses.

  18. Does the augmented Müller-Lyer illusion really lend support to any unrestricted version of this claim? The augmentations create a state of conflict in the noticing agent, and this is our best evidence that under those special conditionsmultiple inconsistent contents are indeed present in experience. It is unclear what, if anything, we should then infer about the unaugmented case.

  19. AC: Sometimes such a division may make sense…perhaps I genuinely experience but don’t notice your new haircut, that is, I experience the shape of your hair, which is new, while not noticing that it is new. But surely parasitic…had my attention been drawn to the shape of your hair, I could have reported all its salient features. This will matter later

  20. A better try: Dretske (2006) asks: How do we tell what enters into conscious visual awareness at some moment in time? Makes a strong case that this is much harder than it seems. If someone reports that yes, they saw (visually experienced) X, and we have no reason to think they are being dishonest, that provides good (not indefeasible) reason to believe that X did enter visual awareness. But failure to report X, and even actively reporting failure to see X, are both way less reliable, for a variety of reasons.

  21. The subjects may simply not be able to issue verbal reports: infants, non-human animals. More interestingly, subjects who CAN issue reports often fail to (a) know what they have seen, or even (b) that they have seen anything at all, even when they have. At root, this all comes about for a simple, but potentially rather important, reason: that seeing is very different from believing! Various examples will focus the ideas….

  22. Not Knowing What You Have Seen To see an X requires little more (perhaps no more) than being able, at that moment on demand, to pick X out by pointing and ask “what’s that?”. But to see an X as an X requires having the concept of X’s, and somehow bringing that concept to bear on the visual experience. Dretske’s favourite old example: You might see a spy every day, but not know you do, as you see Sarah but don’t know Sarah is a spy or you don’t even know what Spies are, [Even the fly you briefly fixate but pay no heed to on your wall might be a spy, genetically engineered by the CIA]

  23. The point of this simple observation is just to stress: “the difference between awareness of a stimulus (an object of some sort) and awareness of facts about it- including the fact that one is aware of it” (Dretske (2006) p.147) Fact-awareness versus Object-awareness Concretely: “ignorance of the fact that one is seeing a spy does not impair one’s vision [that is, one’s conscious experience] of the [object that is a] spy” (148) Object-awareness is in some sense cheaper than fact awareness

  24. Sometimes, however, it seems plausible that visual stimuli can affect us without even any conscious object-awareness… Blindsight cases might be like this. Here, even though subjects can perform above chance on some forced choice tasks, they could never point to the stimulus and ask “what’s that?”: so they fail even the minimal condition on object-awareness that my Fly-Spy case meets. A mistaken suggestion: it might seem that even if you don’t know what you have seen (you lack fact-awareness of X) you should (if you have vision-based object-awareness of X) at least know that you have seen something. But not so…conscious perception can occur even when we think we did not see anything at all…how can this be?

  25. (b) Not Knowing that you have seen anything at all

  26. “suppose S looks at a scene in which there are seven people gathered around a table. Each person is clearly visible. S gazes at the scene for several seconds, runs her eye over (and, in the process, foveates) each person at the table, but pays no particular attention to any of them [ac: perhaps she has been given a different task that incidentally requires this, eg, counting how many are wearing red]. She then looks away. While S is looking away, an additional person--call him Sam—joins the group. Sam is clearly visible [ac: and not wearing red]. There are now eight visible people. When S looks back, [ ac: and even after she foveates each person in turn] she doesn't notice any difference. Having no reason to suspect that a change has occurred, S thinks she is looking at the same group of people. When asked whether she sees a difference in the scene between the first and the second observation, S says, "No." “ (Dretske, 162)

  27. Sounds plausible to me. Simons and Levin have an old case a bit like this, involving a photographer using a manual focus camera..(but someone should do Dretske’s experiment, to be sure!)

  28. Assume that S honestly asserts that she saw no new people at the second viewing. Q/ Did S actually (consciously) see newbie Sam? Q isnot was S aware of the fact that she saw something different (Sam) on the second viewing. She clearly wasn’t aware of any such fact. But did she have object-awareness of Sam? Seems hard to deny it. Dretske hammers it home well…

  29. “S not only saw Sam, but… her experience of him was of the same kind, a conscious experience, as was her experience of the other seven people. She was aware of Sam in the same way she was aware of each of the other seven people around the table. She was aware of the person who made a difference without being aware (realizing, noticing, or believing) that there was this difference…It would be completely arbitrary to say that S consciously sees only the same seven people she saw the first time and that, therefore, her perception of Sam, the new member of the group, is unconscious, subliminal, or implicit. Why just Sam? Why not each of the other seven people at the table?” • Dretske (2006) p.163

  30. “One can be conscious of the objects that constitute a visible difference and not be conscious of the fact that one is conscious of them” (163) • [+ meets minimal condition: she could, on the basis of her current visual awareness, have, had she wished to, pointed at Sam and asked “Who is that?” • Enough object-info entered awareness for this to be possible, unlike the blindsight case..164-5]

  31. Important Caveat: Dretske’s claim is not that you are consciously object-aware of all the elements in a complex scene. Just that “one can be consciously aware of more than one realizes” (164) Fits with his older work on ‘non-epistemic seeing’ I think Dretske is right, and this shows that at least one thing I used to like to say is wrong…(imagine my surprise).

  32. The original array will always comprise six cards of a similar broad type: six face cards, or six assorted low-ranking cards (between about 2 and 6) etc. When the new, 5 card array appears, NONE of these cards will be in the set. But the new 5 card array will be of the same type: all face cards, low cards, whatever. It looks as if ONLY YOUR CARD has been taken. But in fact they are ALL DIFFERENT NOW (so no wonder we got yours!)

  33. (me, 2004) The brain knows that it can USUALLY get detailed information about all the other cards just by looking. So it encodes sth minimal (eg ‘lots of royal cards’) leaving all the detailed info out in the world. This works fine until magicians exploit the laziness.

  34. Me (now) Perhaps we consciously saw much of the detail on each card as it was (not just as ‘royal’) even though we did not notice(perhaps due to motor deference)that they were all new cards second time around.

  35. Many CB cases might well be like these ones, viz, they show only “that sometimes we do not notice some of the things we are consciously aware of” (165) That is, CB failure is not (or not always) a failure of conscious awareness after all.

  36. A reasonable worry: Have we now made ‘visual experience of X’ into something so slippery as to be empirically intractable?

  37. Dehaene et al (2006) • Develop a taxonomy of states according to which the cases Dretske cites would (I think) be classified as preconscious: • “potentially accessible (they could quickly gain access to conscious report if they were attended) but they are not consciously accessed at the moment” (207) • Later, they muse that whether such states are phenomenally conscious but elude report due to being unattended, or are not phenomenally conscious, “does not seem to be, at this stage, a scientifically addressable question” (209)

  38. But consider the famous Sperling (1960) experiments recently discussed by Dretske (2006), Block (2007), Fodor (2007). For a recent version of the exsperiments, see Landman et al (2003) Subjects are briefly (50ms) shown a 3x3 grid of letters T D A S R N F Z B After stimulus is gone, subjects can reliably report (‘full report’ condition) only about 4 letters. But say they saw them all. Should we trust them?

  39. Sperling showed that if rapidly asked instead for the letters in any given row (‘partial report condition’) subjects could often do this, regardless of which row was chosen. So information about each and every letter seems temporarily available, if attention is rapidly so directed, even though the selection of some letters renders the rest (then) unavailable. The experience, various philosophers (Fodor, Block, Dretske) now suggest, contains more information that any full report can display.

  40. Landman et al (2003)(Skip) Subjects shown 8 oriented rectangles for half a second, then gray screen, then the array of 8 but one rectangle may have changed orientation Able to keep track of the orientation of about four rectangles from a group of eight (capacity measure = 4) Yet they typically report seeing the specific orientation of all eight rectangles. BUT with pointer added on gray screen, can track almost all rectangles (capacity measure up to 6 or 7) Possible Exp: Briefly persisting ‘iconic’ experience whose expreiential content exceeds full report See Block (forthcoming) and , for some worries about the exact way Block uses this data, Clark and Kiverstein (forthcoming)

  41. Dretske imagines a similar ‘partial report’ probe applied to his table case. Soon after seeing the second group, someone points to the space around the table where newbie Sam had been placed and asks “was anyone sitting there?”. If she can answer “yes”, we can provisionally conclude she was indeed consciously object-aware of Sam, even though she did not notice the fact that Sam was ‘extra’

  42. Change Blindness (Again) Seeing and Noticing Visual Form Agnosia (Again) Two Types of Conscious Visual Content? A Positive Story

More Related