Abstract
Perceptual illusions have often served as an important tool in the study of perceptual experience. In this paper I argue that a recently discovered set of visual illusions sheds new light on the nature of time consciousness. I suggest the study of these silencing illusions as a tool kit for any philosopher interested in the experience of time and show how to better understand time consciousness by combining detailed empirical investigations with a detailed philosophical analysis. In addition, and more specifically, I argue against an initially plausible range of views that assume a close match between the temporal content of visual experience and the temporal layout of experience itself. Against such a widely held structural matching thesis I argue that which temporal changes we are experiencing bears no close relation to how our experience itself is changing over time. Explanations of the silencing illusions that are compatible with the structural matching thesis fail.
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Notes
For example: the persistence of the Müller-Lyer Illusion (and others) has been claimed to bear on perceptual encapsulation (Fodor 1983); the Ebbinghaus Illusion and its (apparent) failure to influence perceptually guided action has been suggested to speak in favor of two separate visual pathways (Goodale and Milner 1992); and the Waterfall Illusion has been suggested to entail that the content of perceptual experience must be non-conceptual (Crane 1988).
My paper thus responds to a challenge to an empirical investigation of time consciousness once raised by Kelly (2005, p. 230) who said that “[t]here is a simple reason why no empirical work is being done on [the puzzle of temporal experience]. The reason is that we’re not yet clear enough on what kind of work would make progress.” My response proceeds by showing how philosophical analysis and empirical investigation can collaborate to make such progress (even though, of course, no single paper could claim to solve all puzzles about temporal experience).
See what Miller (1984) has called the principle of presentational concurrence PPC (endorsed by Foster 1991; Dainton 2000, 2008, 2010 and Phillips 2008, 2009, forthcoming): “the time interval occupied by a content which is before the mind is the same time interval which is occupied by the act of presenting that very content before the mind” (Miller 1984, p. 107), and also Foster (1991, p. 249): “We have to take experience to extend over a period of real time in a way which exactly matches the phenomenal period it presents”. There is also Dainton (2000, p. 180): “the overlap theory [Dainton’s view of time consciousness, see below] embraces PPC. So even if we draw an awareness-content distinction [which Dainton in the end does not] it makes no sense to suppose that an act of awareness can apprehend a content of a greater temporal duration that itself.” Hoerl’s (2009) “molecularist” (p. 2) reading of the specious present might be understood as endorsing a similar connection (though the issue here is not entirely clear). He says, for example, that his view is one on which “temporal experience is itself a temporally extended process, and there is an explanatory connection between the temporal structure of experience itself and its phenomenology as experience, e.g., as a succession of events.” (Hoerl 2009, p. 2).
My formulation is closely modeled on one in Philips (forthcoming). The idea of a “close match” is supposed to allow for some leeway. My argument against the structural matching thesis will work even if it is read as requiring only that the temporal structure of the content of experience and the temporal structure of experience itself be very similar, and not as the stronger thesis that the two be identical.
That is: these snapshots are experiences as of non-temporal properties.
It is an assumption of the structural matching thesis that anti-realism is false. In order to keep the discussion focused, I won’t, thus, for the main part of this paper discuss anti-realism about time consciousness. See Fns. 37 and 41, though.
A quick note on terminology: Lee (2007, 2008) uses the notion of a “cinematic” picture broadly so as to include, for example, Dainton’s view of time consciousness. Dainton, by contrast, obviously has a more specific cinematic view in mind when he criticizes such views. The same confusion arises for the notion of a “specious present” view. Dainton uses this term to designate almost any realist view of time consciousness (including retentionist views and his extensional model). Tye (2003) and Lee (2008), by contrast, use the term in a more specific way, which excludes Dainton’s view. For reasons of terminological clarity I have therefore mostly avoided talk of the specious present in this paper.
To be more precise, Philips argues that this view follows from the acceptance of four principles (op. cit, p. 94): Realism, Temporal Transparency, Self-Intimation, and Seems → Is. The discussion of the present paper can be read as an extended argument against his Self-Intimation principle that says that (op. cit., p. 94) “[i]f a subject is undergoing perceptual experience of a certain experiential kind, then that subject is in a position to know that they are undergoing perceptual experience of that experiential kind simply in virtue of so undergoing.” Scientific evidence like the one this paper appeals to might strongly support the claim that our experience has certain temporal properties that we were not in a very good position to know about simply in virtue of undergoing this experience. With the help of this evidence we can get a grip on the temporal structure of experience indirectly, and not via considering the content that experience represents.
This is because, on Phillips view, experience does not represent metrical durations at all.
In the luminance condition the dots change smoothly from bright to dark, in the size condition they change their size, in the shape condition their shape smoothly morphs from (roughly) a star shape to a (roughly) round shape. For a precise description of the relevant parameters see Suchow and Alvarez (pp. 3–4). Everything I say applies mutatis mutandis to the illusions of changes of luminance, size and shape as well.
The conditions last longer than one cycle around the color wheel.
Throughout this paper, I will discuss the silencing effect as a form of visual illusion. Following Block (2010), someone might doubt, though, whether there is one way to see (apparent) change correctly. If our experience represented absolute metric properties such as changing from red back again to red, say, in one second, then of course the experience would be correct just in case it represented a change that is in fact happening during one second as happening during one second. But if our experience did not represent such metric properties (which is plausible), then why say that veridical perception of change occurs in the stationary condition and not in the rotation condition instead? The rate of change in one condition appears slower as the rate in the other. But which experience should we count as getting the actual rate of change right? In a related context, Block considers the effects of attention on appearances: with attention, for example, objects look to have higher apparent contrast than without attention (Carrasco et al. 2004). Yet, Block argues that this difference in apparent contrast does not imply a difference in correctness conditions. If one were persuaded by this argument, one might run a similar argument for the present case: while in the rotation condition the dots appear to change color slower than in the stationary condition this is not accompanied by a difference in correctness conditions. Indeed, it seems that given the vivid and sizable effect in the present case (up to 10× decrease in apparent rate of change) compared to the rather small effects of attention on, say, apparent contrast (an increase of about 8 %, which is barely above the just noticeable difference) Suchow’s and Alvarez’ silencing results in one sense indeed might be better suited for Block’s purposes. While the issue is interesting, this is not the place for an extended discussion of the connection between Suchow’s and Alvarez’ results and Block’s argument. Nothing in my discussion in this paper will hang on the further philosophical issue discussed in this footnote.
Note that there might be some lag of your experience (i.e. you might experience the dot as having the color it in fact had, say, 20 ms ago). This lag in fact probably depends on the speed of rotation (see Suchow and Alvarez for relevant data and discussion). Nothing in my argument will depend on the existence, size or rotation dependence of such a small lag.
Though it is no assumption of my argument that you are experiencing each dot individually (See Fn 32).
In addition, the fact that subjects experience a slower rate of change in the rotation condition also shows that a proponent of the structural matching thesis would not be able to retreat to a claim about a merely necessary (but not sufficient) condition for the experience of change like the following: as long as you experience any changes at all, the rate at which your color experience is changing matches the rate of change of color you are experiencing. If my interpretation is correct, Suchow’s and Alvarez’ illusion demonstrate that the rate at which your experience is changing and the rate of change you are experiencing are able to vary quite independently of each other.
Since the effect is gradual and the experience of change rarely stops completely, it might be even more appropriate to speak of dampening the experience of change.
Suchow and Alvarez (p. 1) cite empirical evidence of such temporal freezing in some other conditions (see citations therein).
Based on earlier experiments by others (see citations in Suchow and Alvarez).
In the flip experiment the dots first rotate for about 2 s (see Suchow and Alvarez, suppl. material to Exp. 3). Though Suchow and Alvarez did not explicitly test for this, the assumption is that during the 2 s before the flip the subject’s experience is the same as in the rotation condition without a flip (after all, there is a fact about the temporal content of your experience during such a long interval (even if not within very short intervals, say, below 500 ms), and that fact does not depend on what will happen in the future). This also seems to be what subjects report. The independence of the experience during the time before the flip from that future flip is confirmed further by flipping experiments under three conditions that differ in what happens after the flip: in one the dots continue to rotate after the flip, in one they stop rotating, and in one they are replaced by a checkerboard mask. Suchow and Alvarez find that what happens after the flip makes no qualitative difference to whether subjects notice the flip. A final note about the flip experiment: while the experiment was performed at a single rotation speed (75°/s), the independence of the present experience from the future flip also implies that subjects would experience faster color changes at slower rotation speeds just like in the original rotation condition.
Which is what is usually called the noticeability threshold (or just noticeable difference JND). This is only about double (maybe three times) the just noticeable difference for color in optimal viewing conditions which is usually around 2–4 nm (measured in physical wavelength) which corresponds to roughly 4°–10° on the color wheel (see e.g. Shevell 2003). Even under the assumption that viewing conditions are optimal in the stationary condition (which they probably are not, due to crowding) a difference in JND between the two conditions thus is unlikely to fully explain the experience of slowing down by a factor of up to 6–8 (in the case of a rotation speed of 75°/s). Nevertheless, it would be very interesting to test whether there is a difference in JND between the two conditions. Even better, future research should compare the distributions of “noticings” (like Figs. 2, S4 in Suchow’s and Alvarez’ paper) at various rotation speeds and compare them to the distribution found for the stationary condition. Such a comparison could reveal the temporal fine structure of experience in the various conditions (preliminary results by Jordan Suchow (personal communication) suggest that the distribution of noticings is not wider in the rotation condition than in the stationary condition).
Of course, we know from Duhem and Quine that any theory can be preserved in the face of any piece of evidence. A good empirical argument against the structural matching thesis thus need not be a demonstrative argument.
Thanks to discussion of this point with Enrico Grube, Brian Scholl, and to an anonymous referee of this journal. They convinced me of the importance of this type of proposal. Thanks also to Jordan Suchow for helping me to see its shortcomings.
The numbers provided here are just stipulation. Finding the correct number would, of course, be a matter of empirical investigation.
Suggested to me by an anonymous referee of this journal.
Thanks to Farid Masrour for this point.
Online at http://vimeo.com/18074447.
Hypothesized by Suchow and Alvarez themselves (2011a, p. 3). Indeed, if you focus attention on any particular dot (and, thus, plausibly get more information about it), the effect visibly disappears for that dot. See also Nanay (2010) and Stazicker (2011) for a proposals about the connection between in-attention and indeterminacy in the contents of experience.
See Simons (2010) for a proposal in this vein.
By contrast, when we see a colored object in dim lighting conditions, we do not see it as being brightly colored. As long as we do see it as being colored at all, we seem to see it at least as being more red-ish or blue-ish.
There is another type of indeterminacy one might think of. One might suggest that the relevant indeterminacy—rather than lying in the color each dot is experienced as lies in your experience of the whole display of dots (just like you might see an arrangement of speckles on a hen without seeing each individual speckle, or just like you might weigh a bunch of marbles without weighing each individual marble, you may see an arrangement of colored dots without seeing #53. This suggestion thus would mirror one by Tye (2010) in response to an argument by Dretske (2004)). You have an experience as of a ring of colored dots that is rotating; a visual experience as of them (the dots understood collectively); but, so the proposal, it does not follow from this that you have an experience of, say, #53, even though #53 is one of the dots. Thus, so the objection, your experience in the rotation condition should be described as an experience as of non-uniformly colored dots, while in the stationary condition you have an experience as of each dot individually (or, at least, a spatially more determinate representation of the ring of dots). Reply: while this (like color indeterminacy) might be a difference between the two conditions, the proposal does not do justice to all of the phenomenal and experimental data. There is a difference in temporal experience. The phenomenal difference between the two conditions still seems to be—roughly—that in the stationary condition you had an experience of fast color changes while in the rotation condition you experience slower color changes. The appearance of the whole display does not (at least not just) become less determinate in the rotation condition, the “pulsing” experience of color changes of the whole display that is phenomenally manifest in the stationary condition is slowed down in the rotation condition. To remind us: when Suchow’s and Alvarez’ subjects were asked to compare “the rate of change” (p. 3) in the rotation condition to the rate of change in the stationary condition, they indicate a slowing down. The present proposal thus, again, directly flouts the subject’s reports and is incompatible with the phenomenal data.
In fact, in a sense the illusion is better thought to be closely connected to in-attentional blindness (you fail to see changes if you don’t attend to them). Yet the experience of slowed down changes in the absence of attentional resources (like the experience of shorter duration in Tse et al. 2004) shows that the effect of absent attention on time consciousness is more specific than to make the subject “blind” to the changes in front of her eyes. Dretske’s account of change blindness though is what is relevant to the present proposal. Thanks for an anonymous referee of this journal of suggesting to discuss this point.
Dretske himself acknowledges this limitation of his proposal (Dretske 2004, p. 16, Fn 6).
This is in contrast to the oddball effect. New and Scholl (2009) have provided strong evidence that subjects judge the time of every event in the visual field as longer if one oddball occurs in it. The oddball effect thus is global and therefore it is impossible to experience different durations of two stimuli at the same time if one is an oddball and the other one is not (this would be so, even if—in contrast to Phillips’ view—the experiential and not the cognitive explanation of the oddball effect were correct).
See the discussion in Phillips (2009).
The same considerations also bear on an anti-realist snapshot model. Because the color changes you are experiencing seem to vary quite independently of how your color experience itself is changing over time, the silencing effect shows that the experience of change is not a phenomenally idle wheel.
This is how the terminology is used by Broad and Tye (as well as by Phillips 2008, 2009, forthcoming). Lee calls the view the instantaneous specious present view. Chuard (2011) calls the principle the present view accepts “content temporal extension” (p. 5). The terminology in this area, unfortunately, is again very confusing. Barry Dainton, for example, speaks of his own extensional model (which accepts the structural matching thesis, see Sect. 2 above) as well as of the retentional model (see below) also as “specious present” views (see Dainton 2000, 2008, 2010). I here use the terminology in the more narrow sense (as in Tye, Lee and Phillips).
How long an experience as of some temporal property needs to last is a strictly empirical question just like the question how long an experience as of, say, a shape property lasts. The specious present view thus can, but need not, accept the so-called principle of simultaneous awareness (Miller 1984) that says that “if one experiences succession or temporal structure at all, then one experiences it at a moment.” (Phillips 2009, p. 179).
Note that holistic temporal atomism in principle could also be an anti-realist view claiming that there is no experience as of temporal properties at all. This anti-realism would need to provide a plausible account of the evident phenomenal difference in something like color dimension between the stationary condition and the background motion condition (the difference in the location dimension evidently is not the striking visual effect subjects experience). Much of the discussion in Sect. 5 shows that it will be difficult to explain this phenomenal effect without reference to the experience of change. In this sense, then, my discussion also puts pressure on anti-realism about the experience of time.
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Acknowledgments
I would like to thank George Alvarez, Ned Block, Enrico Grube, Sean Kelly, Farid Masrour, John Morrison, Brian Scholl, Susanna Siegel, and especially Jordan Suchow and an anonymous referee for this journal. Previous versions of this material have been presented at the joint meeting of SPP and ESPP in Montreal 2011 and at John Morrison’s seminar on the Philosophy of Perception at Columbia University in 2012. Thanks also to the participants of these events for their helpful input.
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Watzl, S. Silencing the experience of change. Philos Stud 165, 1009–1032 (2013). https://doi.org/10.1007/s11098-012-0005-6
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DOI: https://doi.org/10.1007/s11098-012-0005-6