Perceiving Temporal Structure

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Perceiving Temporal Structure

by Elliot Carter

A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy

Department of Philosophy University of Toronto

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Perceiving Temporal Structure

Elliot Christopher Carter Doctor of Philosophy Department of Philosophy

University of Toronto 2020

Abstract

Perceptual experience seems to present us with not only objects and their ‘static’ properties such as shapes, colours, and positions but also with eventsand their temporal structure: that is, their temporal relationships such as simultaneity and temporal order. This dissertation aims to defend the claim that we perceptually experience temporal structure from recently revived challenges, and to show how a theory of temporal perception bears on central issues in the philosophy of mind.

Experience manifestly possesses its own temporal structure. If we have perceptual experiences of the temporal structure of external events, it seems natural to ask whether there is a deep explanatory connection between the temporal features of the experiences themselves and the temporal features that they are experiences of. Accordingly, much of the philosophical debate about temporal perception focuses on the matching thesis: the claim that the temporal structure of perceptual experience always matches the temporal structure that one experiences events as having. Debate between critics and proponents of the thesis can sometimes appear to be stuck in a clash between experimental results and strongly held introspective intuitions about experience. I do not directly argue

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against the matching thesis, but I show how we can improve upon existing experimentally-based arguments against it. I also show how its critics can explain (rather than simply disregard or deny) the intuitions that allegedly support it. Trying to explain these intuitions from the critic’s perspective suggests new ideas about temporal perception that are not only coherent but independently plausible. I develop these ideas and show how they can deepen our understanding of how temporal perception fits with other issues central to the philosophy of mind: our introspective awareness of our experiences, the connection between perception and the temporal present, and perception’s role in guiding action.

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Acknowledgements

In writing this I benefited greatly from the help and support of many people. My largest debt is to my supervisor, Mohan Matthen. He was a tireless reader and commenter, unfailingly generous with his time and effort. His advice led to innumerable improvements, big and small. I owe a debt of gratitude to the rest of my committee as well. Bill Seager’s sharp questions frequently helped me to see clearly what I had misunderstood or overlooked, and his enthusiasm and inquisitiveness helped me to focus on what was interesting and important. And Diana Raffman was a careful reader, whose suggestions were invaluable; I can only hope to imitate her clarity, precision and style as a writer. Imogen Dickie also served as a member of my committee before moving to the University of St Andrews. She helped me greatly in refining my questions and arguments, and demonstrated a standard of intellectual rigour that gave me something to aspire to.

I was lucky enough to spend a semester at the University of Warwick as a visiting graduate student under the supervision of Matthew Soteriou. His incisive comments helped to focus and shape the project. During this time, I also met with Christoph Hoerl and Ian Phillips, both of whom generously read my work and gave insightful feedback. I am grateful to my internal examiner, Michael Miller, and my external examiner, Barry Dainton. Although my work falls outside his usual focus, Michael’s questions and comments raised important methodological issues that got right to the heart of the project. And Barry’s philosophical skill and expertise on my topic shone through in his

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questions and comments. He obviously read the dissertation with a level of care that went above and beyond, and his feedback was invaluable.

Much of my philosophical inspiration comes from the community of graduate students (current and former) at the University of Toronto. Thanks (in no particular order) to Dave Suarez, John Bunke, Julia Jael Smith, Mark Fortney, Sean Michael Smith, Jessica Wright, Damian Melamedoff, James Davies, Luke Roelofs, Lisa Doerksen, Manish Oza, Melissa Rees, Clinton Debogorski, Rory Harder, Catherine Rioux, Matthieu Remacle, Eric Mathison, Michaela Manson, Daniel Munro and Zachary Weinstein. Special thanks are due to Aaron Henry, Mason Westfall, and Dominic Alford-Duguid, conversations with whom were especially helpful in shaping and reshaping my project. Thanks also to Evan Westra and Michael Barkasi, who were post-docs at U of T during the past year and who gave me extremely helpful feedback. I would also like to thank a few faculty members who, while not officially involved in my project, helped me in some capacity along the way: Gurpreet Rattan, Benj Hellie, Jessica Wilson, Marleen Rozemond, Jennifer Nagel, and Mark Kingwell. Thanks also to Margaret Opaku-Pare and Mary Frances Ellison, without whose administrative assistance I doubt this dissertation would exist.

I presented portions of this work to audiences at the CPA in 2016 and 2018 and the APA Central in 2018. Thanks to audiences on those occasions, and thanks especially to my commentator at the APA Central, Joseph Neisser. Thanks to Daniel Dennett and the audience at the Workshop on Daniel Dennett at the University of Antwerp in 2018, organized by Bence Nanay. Special thanks to Gerardo Viera, who provided extremely valuable comments and feedback on (what is now) Chapter 2, some of which prompted major, much-needed revisions.

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Outside of philosophy, I am grateful to Laurence Harris, who met with me to discuss my interest in his psychological research on perceiving simultaneity, and his collaborator Vanessa Harrar, who generously corresponded with me about her work.

I was a fellow at the Jackman Humanities Institute during the 2016-2017 academic year, and I benefited greatly from the experience. I was also a member of a virtual dissertation group organized by Joshua Smart. Thanks to Géraldine Carranante for helpful written comments.

A wholehearted and earnest thanks to my parents, Patrice and Kevin, and my brother, Lewis, who have been an unwavering source of support. Thanks also to my wife’s parents, Fran and Konrad, and her sister, Kyra. Their enthusiasm and support have been inspirational. And finally, I am eternally grateful to my wife, Alexandra. I could not (and would not) have done this without her encouragement.

This research was supported by the Social Sciences and Humanities Research Council of Canada.

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Introduction

Consider the following cases of perceptual experience:

• The experience of watching a car begin to accelerate at an intersection.

• The experience of hearing a guitarist raise the pitch of note by bending a string.

• The experience of feeling someone run a finger across your back.

In each of these cases, you seem to be perceptually aware of how things are at certain moments, but also of how things change over an interval. You see the colour, shape and position of the car, but you seem also to see how the car’s position changes—you see it move. You hear the timbre, loudness and pitch of the note, and you seem also to hear how those qualities changeas the string bends. You feel the pressure of the finger against your back, but you seem also to feel the way the location of the finger’s contact with your back changes.

These cases seem to demonstrate that we have perceptual experiences of temporally extended events, and that part of what it is to perceptually experience an event is to experience the relations of temporal order, or simultaneity, among the temporal parts of the event. For example, you seem to see the car as moving from some location to another, and this seems to involve experiencing the car as being at the first location before the second. Likewise, you seem to hear the string as ringing at a lower frequency before it rings at the higher frequency, and you seem to feel the finger as touching your back at some location before another location. I will use the term temporal structure for these aspects of experience.

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This dissertation is about the perceptual experience of temporal structure. In Chapter 1, I argue that examples like these indeed show what they seem to show: that we genuinely perceive temporal structure. I criticize alternative proposals on which perceptual experience consists in a series of ‘snapshots’ that do not portray temporal relations. The remainder of the dissertation focuses on the question of how experiences of temporal structure should be explained.

The key philosophical question about experiences of temporal structure is what role the temporal characteristics of the experiences themselves ought to play in their explanation. The possibility of asking this kind of question distinguishes temporal experience from experiences other kinds. For example, we do not ask whether the shape of an experience (if there is such a thing) helps to explain how it could be an experience of the shape of objects, or how its colour might explain how it presents us with their colours. But time seems different. Experience manifestly possesses its own temporal structure, and many philosophers have wondered whether there is a deep explanatory connection between the temporal structure of experience and the temporal properties that we experience. Accordingly, much of the philosophical debate about temporal experience has focused on the matching thesis: the claim that the temporal structure of perceptual experience always matches the temporal structure that one experiences events as having. According to the thesis, a perceptual experience of a flash preceding a bang always consists of an earlier experience of the flash and a later experience of the bang. Note that the alleged match is between the temporal properties of one’s experience and the temporal properties that one experiences. It is not a match between the temporal properties of experience and the temporal properties of the external events that cause one’s experience (the thesis applies in cases of illusion and hallucination). According to the thesis, experienced temporal order matches the temporal order among one’s

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experiences. It is not possible to experience successiveness ‘all at once’; one’s experience of a succession must itself be successive.

To many, the matching thesis seems highly intuitive. Phillips (2014a) calls it the ‘naïve view’ of temporal experience and considers it an article of common sense that we should not give up without good reason. Even Lee, a critic of the thesis, admits that it is favoured by our “prima facie intuitions” (2014a, 6).

However, many philosophers have thought that the intuitive appeal of the thesis traces back to an error: a conflation between the properties of one’s experience itself and the properties that one experiences. In a representative passage, Dennett and Kinsbourne write:

In general, we must distinguish features of representings from the features of representeds…. [S]omeone can shout "softly, on tiptoe" at the top of his lungs, there are gigantic pictures of microscopic objects and oil paintings of artists making charcoal sketches. The top sentence of a written description of a standing man need not describe his head, nor the bottom sentence his feet. To suppose otherwise is confusedly to superimpose two different spaces: The representing space and the represented space. The same applies to time. (Dennett and Kinsbourne 1992, 188)

In non-temporal cases of perception, Dennett and Kinsbourne’s insistence on a representing/represented distinction seems obviously correct. No one thinks that when they visually experience a round, blue object, their experience itself is literally round and blue. Nor does anyone think that when they have a tactile experience of a heavy object in their palm, the experience is literally heavy.

Part of the reason these suggestions seem wrong is that we cannot really make sense of them. Perhaps one’s experience really has such properties as colour, shape and

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weight (e.g., if they are identical to temporal parts of brain regions that have such properties), but these properties seem obviously irrelevant to explaining how one has experiences of colour, shape and weight: the brain does not turn blue when you see something blue, and even if it did, this would not help to explain the experience of something as blue. But, as I have suggested, temporal properties are different: experience is obviously a kind of process that unfolds over time (Phillips 2014a). Philosophers who accept the matching thesis are not guilty of a naive conflation between the temporal properties of experience and those of the experienced. They are putting forward a sensible (and, I will argue, testable) hypothesis about the nature of their relationship, one that is grounded in phenomenological intuitions that are worth taking seriously and critically. It is a worthwhile philosophical question whether the experience/experienced distinction applies the same way in the temporal case.

So: what would it take to determine whether it does? Answering this question is the project of Chapter 2. My answer will be that the matching thesis can be tested using the methods of psychophysics. I will argue that existing arguments against it based on experimental results are flawed, but that the thesis does generate testable predictions because it puts constraints on how the perceptual mechanisms underlying our awareness of simultaneity and non-simultaneity must work. I will explain how these predictions can be put to the test.

Do the phenomenological intuitions taken to support the matching thesis survive philosophical scrutiny? This will be the question guiding Chapters 3 through 5. I will argue that we can explain away the apparent phenomenological case for the matching thesis without accusing its proponents of a crude vehicle/content confusion. In Chapter 3, I propose an indirect model of how we introspect temporal features of perceptual experiences, where our awareness of the temporal properties of our experiences is

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mediated by our awareness of the temporal properties of our stream of non-perceptual mental events (like judgments and volitions). The indirect model is favoured by the

temporal transparency claim: the idea that when we introspectively attend to perceptual experience, the only temporal features that seem available to attend to are those of the events we experience (the temporal features of experience itself seem not to be directly introspectively accessible). I will argue that the model can explain how the matching thesis could appear to be correct even when it fails to be true over very brief intervals: there is no guarantee that experience’s temporal structure really is as it (indirectly) appears all the way down to the millisecond level.

Next, I turn to another potential source of phenomenological support for the thesis: the connection between perceptual experience and the temporal present. I suggest that part of the intuitive appeal of matching comes from the idea that perceptual experience presents events as present, and that this idea can seem incoherent (or at least implausible) if we reject the matching thesis. Roughly, the reason is that if the matching thesis is false, then we can experience a succession of events ‘all at once,’ but by hypothesis, we also experience each event in the succession as present. If we simultaneously experience each event as present, then it is at least difficult to understand how we could also experience them as successive. But I will argue that the appearance of a problem here is the result of a mistaken (if intuitive) assumption about perceptual experience’s connection with the temporal present. In Chapter 4, I argue that the felt present-orientation of perceptual experience in fact reflects the characteristic role that perceptual experience plays in guiding action, and that the temporal present is no part of

what we perceptually experience. Then, in Chapter 5, I argue that this account of the connection between perceptual experience and the present is consistent with the falsity

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of the matching thesis. We do not need to accept it to explain perception’s present-orientation.

Philosophical arguments about temporal perception usually begin with either phenomenological premises or premises about the results of psychological experiments. Typically, the former kind of argument has been taken to support the matching thesis, and the latter its denial. Although I do not directly argue that the thesis is false, an overarching theme of this dissertation is that the phenomenological case for it, although not based on a simple conflation between representing and represented, is much weaker than has often been supposed. The intuitions taken to support the thesis can be explained on alternative views. And the picture of temporal perception that emerges when one does so is both coherent and independently plausible. From the perspective of a critic, taking seriously the phenomenological evidence for the matching thesis forces a re-examination of the way that temporal perception fits with other phenomena central to our understanding of the mind: our introspective awareness of our experiences, the connection between perception and the present, and perception’s role in guiding action.

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Chapter 1 Do We Perceive Temporal Structure?

Naive introspection suggests that we perceptually experience temporal relationships among events such as simultaneity, successiveness, and temporal priority: in other words, temporal structure. Evidently, we can perceptually experience things moving as well as changing in qualities like size, colour, pitch, loudness, temperature, pressure and so on. You see the car move; you hear the speaker’s voice quaver; you feel the plane lift off. Among other things, these seem to be experiences of temporal structure. When you perceptually experience something as moving from one location to another, or as having one property and then another, it seems that you are perceptually aware of a temporal relationship between two or more states of affairs.

Most of this dissertation will focus on philosophical theories that attempt to explain how perceptual experience presents us with the temporal structure of events. But this chapter will focus on defending the supposition that we experience temporal structure in the first place. One might wonder why this claim needs any defense. Why are examples like those given above not sufficient to conclude that temporal structure is a perceivable aspect of the world? One would not normally begin a project on, say, the perceptual experience of colour with a lengthy defense of the claim that we have colour experiences, since it is so obvious that we do. What makes temporal structure different?

The answer is that in the recent and not-so-recent history of thinking about temporal experience, a number of philosophers have denied that temporal relations can be perceived. Instead, they have argued that what we perceptually experience is always exhausted by how things are at a moment. Strictly speaking, on such views we never

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perceive events as occurring simultaneously or in succession. Such theories are all versions of what is called the snapshot theory of perceptual experience.1

The classic version of the snapshot theory—what I will call the static snapshot theory—outright denies that we have experiences of motion or change. This version of the theory seems to be impossible to square with ordinary intuitions about perceptual experiences. Recently, however, philosophers have constructed a version of the theory that respects those intuitions and aims to explain them, while holding onto the claim that perceptual experience concerns only what goes on at a moment. This new version of the theory—the dynamic snapshot theory—claims that although we perceptually experience only momentary property instances, those properties can include ‘dynamic’ properties such as moving at a time and rising in pitch at a time. On this view, you can visually experience an object as moving, but not, strictly speaking, as being in one location and then another. If this is right, we can perceptually experience motion, but can experience changes in location only by comparing what we perceptually experience with what we remember.

In this chapter, I aim to refute both forms of the snapshot theory. I begin by contrasting the claim that we experience temporal structure with certain logically stronger claims about how we experience it. Then, in Section 1.2, I introduce and criticize the classic, staticsnapshot theory. In Section 1.3, I introduce the dynamic snapshot theory, and assess its explanation of motion experience, which is motivated by certain temporal illusions (motion aftereffects) that seem to show that one can experience motion without

1_{The snapshot theory is sometimes called the}_{cinematic model}_{, since it suggests that our awareness of} motion is caused by a succession of static ‘frames’ of experience (Dainton 2018).

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experiencing anything as changing position. I argue that, contrary to what its proponents claim, these illusions do not provide strong support for the theory’s explanation of motion experience. Still, the theory is at least viable as an explanation of motion experience. But if it is to succeed, it needs to explain every type of temporal perceptual experience, not just that of motion. In Section 1.4, I argue that the theory cannot be extended to other cases of temporal experience, and so the snapshot theory—even in its sophisticated, dynamic form—is false.

1.1 What Does It Mean to Say That We Perceptually Experience Temporal Structure?

My claim is that at we have perceptual experiences of temporal structure: that is, of temporally extended events and temporal relationships among events. This claim should be distinguished from stronger ones about how we perceive temporal structure. Sometimes philosophers have rejected the claim that we perceive temporal structure because they have mistakenly attributed to it implications of some stronger view. Hence, it will be important to get clear on the commitments of the claim.

First, I want to emphasize that the question of whether we perceptually experience temporal structure does not presuppose any particular account of the phenomenal character of perceptual experience. For example, suppose one takes a representationalist

view of perceptual experience, on which the phenomenal character of an experience (the way it feels to its subject, which constitutes ‘what it’s like’ to have the experience) consists

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in its representational content (a way that the experience represents the world as being).2 For the representationalist, the question arises as to the kinds that figure in the representational content of experience, and hence constitute its phenomenal character (Siegel 2010). The question this chapter addresses is an instance of this general question. For the representationalist, we are asking whether temporally structured properties and relations enter into the phenomenology-constituting content of experience.

We can make sense of the question on other views also. For the naive realist, the phenomenal character of a (veridical) perceptual experience is constituted by a perceiver, an external scene consisting of objects and their properties, and various aspects of the perceiver’s perspective on the scene.3_{But not every property of a perceived object will} figure into phenomenal character; objects have many properties that do not contribute to how they appear in perception. So, on the naive realist view, the question I have posed should be understood as the question of which properties of the scene can partly constitute the phenomenal character of one’s experience. Can it include the temporal arrangement of events?

On indirect theories, the phenomenal character of perceptual experience is constituted by narrow, non-representational characteristics of one’s mental state. For example, on sense-data theories, phenomenal character is constituted by special, mind-dependent objects and their properties, which are the objects of one’s direct perceptual awareness. On mental paint theories (Block 1996), phenomenal character is constituted by

2_{For examples of representationalist views, see Harman (1990), Tye (1995), Dretske (1995), Byrne (2006),} Siegel (2011) and Chalmers (2011).

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the intrinsic properties of one’s experiences. Sometimes these are the properties in virtue of which the experience represents the world (what Block calls ‘mental paint’), and sometimes they are irrelevant to what the experience represents (what he calls ‘mental latex’). For indirect theories, we should understand the question of this chapter as asking whether there are intrinsic features of perceptual experiences (or of sense data), the direct awareness of which amounts to an awareness of temporal structure.4

Another clarification is that the claim that we perceptually experience temporal structure allows for a variety of views about the relationship between the temporal structure of events as we experience them and the temporal structure of perceptual experience itself.5_{One’s stream of conscious perceptual experience is a kind of temporally} extended event with a temporal structure of its own; if we do have experiences of temporal structure, we can ask how they are related to the temporal structure of our experiences of them. According to extensionalist theories, one’s perceptual experience is of a temporally structured event (partly) because the experience itself possesses that same structure (so an experience of B following A always consists of an experience of A

followed by an experience of B) (Dainton 2000; Phillips 2009, 2014a). According to

retentionalist theories, we have experiences of temporal relationships between events, but

4_{Presumably for indirect theorists, these intrinsic features would simply be the temporal structure of the} experiences themselves. But we can leave it as an open question for now whether there could be some other feature of experience that plays this role. For example, Dainton (2018) critically discusses Broad’s (1938) view on which experience involves present ‘acts’ of awareness of the past, where the apparent temporal location of their objects depends on the degree of ‘presentedness’of the act. Presentedness is supposed to be a phenomenal feature that the mental act possesses in the present. So, on this view, awareness of temporal structure seems to constitutively involve awareness of intrinsic, non-temporal features of our experiences. Dainton finds it mysterious how any such feature could explain the appearance of temporal structure, but we can at least register this as a possible view an indirect theorist might take.

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such experiences are always momentary (Broad 1923; Brentano 1998; Husserl 1991).6_Such a view requires that we distinguish the temporal properties of our experiences from the temporal properties of experienced events. On such views, an experience of B following

A is a momentary occurrence which represents that B follows A. Retentionalism is one form of what Lee (2014a) calls atomism, which is the view that the temporal structure of perceptual experience does not match the temporal structure of the events we experience. Retentionalist theories deny such a match, since they view temporal experiences as momentary states of awareness, but this much is true also on theories according to which experiences are temporally extended but do not match the temporal arrangements of the events experienced. The arguments I will offer in this chapter support the fundamental tenet common to extensionalism, retentionalism, and atomism—namely, commitment to experiences of temporal structure.

The distinction among extensionalism, retentionalism and atomism is familiar in the temporal experience literature, but there are other theoretical options concerning how we perceive temporal structure that have received less attention. Here, I have in mind a distinction between what I will call the temporal window view and the event specific view. Roughly speaking, the distinction is between a view on which we experience intervals of time as being ‘filled in’ with events from all sensory modalities and their temporal relationships, and a view on which we experience events and their temporal relations in a piecemeal way. On the temporal window view, if your overall perceptual awareness includes two events, it necessarily speaks to how they are temporally related, whereas on the event specific view, it might not.

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The temporal window view postulates a temporal field of awareness, analogous to the visual field but extended in time rather than space.7_{This view supposes that there is} some interval such that your overall perceptual experience always includes modality-specific experiences of events that seem to occur within that interval, and you experience

all combinations of such events as standing in particular temporal relations to each other. For example, you might have a constant experience of a 100-millisecond temporal field, such that your current perceptual awareness would always include what you visually experience over that interval, as well as what you feel, smell, taste, and so on. Moreover, you would always experience these events as temporally related (just as, necessarily, you seem to experience items within your visual field as spatially related). To illustrate, if your current visual awareness was of a pair of successive flashes and your current auditory awareness was of a pair of successive tones, then you would necessarily also experience temporal relationships between the flashes and the tones—for example, your experience must apparently settle whether the first flash occurs before, simultaneous with, or after the first tone, and so on.

On the alternative, the event specific view, your current awareness might include certain events that you do not experience as temporally related. In the example, you might visually experience the flashes as successive and auditorily experience the tones as successive without experiencing any temporal relationship between the flashes and the tones. This is not to say that you experience those events as temporally unrelated—the

7_{This idea might be part of what James (1890) has in mind in his well-known discussion of the}_specious

present doctrine. I have given the idea a different name here to distinguish it from the stronger claim that everything one experiences within the temporal field is experienced as temporally present. I discuss the present-oriented nature of perceptual experience in Chapter 4, and its connection with the specious present doctrine in Chapter 5.

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absence of awareness is not the awareness of absence. It could be that your experience is simply silent on certain questions about how events are temporally related.

The temporal window view and the event specific view disagree over the kinds of experiences that are possible because they disagree over how temporal perception works. The temporal window view is committed to a model of perceptual processing on which we are always aware of an interval of time and of the temporal relationships within it, and perceiving the temporal relationships is a matter of the perceptual system locating events within that interval. Imagine a timeline with a built-in scale relating distance on the line to duration. Once you have plotted an event on the line, you do not need to do anything else to represent how that event is temporally related to the other events you’ve plotted. And you cannot plot an event on the line without thereby representing those temporal relationships. The temporal window view suggests a model on which the perceptual system always begins with a segment of such a line, and then plots perceived events on it.

The event specific view denies that we perceive an event by locating it within an already given interval, where the experience of temporal relationships to other perceived events is an unavoidable consequence of determining its location. Rather, this view supposes that the perceptual system must recognize temporal relationships in a piecemeal way, somehow labeling events as simultaneous or as successive without locating them within a temporal window. Over some interval of experience, the perceptual system might represent events A, B, C and D. But, because it does not need to locate them on a shared timeline, it might represent temporal relationships between A

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and B and between C and D without representing the temporal relationships between, e.g., A and C.8

The distinction is analogous to a distinction between maps and sentences as representations of space. Maps, as Camp puts it, “automatically conjoin information about the spatial location of all the objects and properties they represent” (2007, 161). Sets of sentences do not automatically conjoin spatial information in this way, in the sense that you can understand a set of sentences about some spatial facts without thereby understanding the spatial information implied by their conjunction (you might, for example, understand a set of directions without automatically understanding the spatial relationship between the point of departure and the destination). According to the event specific view but not the temporal window view, perceptual experiences of temporal relationships do not automatically ‘conjoin’ in this way either. The point here is not that perceptually experiencing temporal relationships is very much like being confronted with a set of sentences. Rather, it is that temporal awareness in perception might be limited, in a way analogous to the way that our understanding of the spatial information encoded in a set of directions can be limited relative to that achieved by seeing the directions represented on a map.

8_{Arstila (2018) criticizes the idea that we perceive temporal structure on the grounds that such a view} implies that “the end of an event lingers in our consciousness for as long as the specious present [i.e., the temporal window] lasts” (7). He says that this claim conflicts with experimental findings by Di Lollo (1980) that seem to show that how long an event persists in perceptual processing (for the purposes of certain psychophysical tasks) depends not on how recently the event ended, but rather on when it began. Whatever merits this argument has, it is not an argument against the general claim that we perceptually experience temporal structure; it is at best an argument against the temporal window view. The event specific view involves no commitment to the idea that all perceptually experienced events linger in our consciousness for a set amount of time. See Shardlow (2019) for other criticisms of Arstila’s argument.

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Now we can better understand the commitments of the view that we perceptually experience temporal structure. The view commits us to the idea that we have perceptual experiences of events and of temporal relations between them, but it does not commit us to any view of how experience itself is temporally structured, or to the idea of a temporal ‘field’ akin to the visual field, or to any view of how ‘rich’ or ‘sparse’ our experience of such temporal relations is. We might, as philosophers sometimes assume, perceptually experience a temporal window filled in with events and their temporal relationships, or we might experience temporal relationships in a more piecemeal way. Perhaps the perceptual system tracks temporal relationships within sense modalities but not always between them, or within certain types of events (as we shall see in Section 1.4, phonemes seem to be a plausible example), but not always between separately processed events. Or perhaps experience is ‘rich’ with temporal information about events within the focus of perceptual attention but not outside of it. The claim that we experience temporal structure leaves open these theoretical options.

1.2 The Static Snapshot Theory

According to the static snapshot theory we perceive only momentary states of the environment and we have no perceptual experiences of such phenomena as motion, change, or persistence. Such a view is often attributed to Reid, who claimed that “if we speak strictly and philosophically, no kind of succession can be an object either of the senses or of consciousness” (1855, Essay III, Chapter V). Although this phenomenally conservative position has few contemporary defenders, Chuard endorses the view that

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“an experience can only represent what happens at a given time” (2011, 8-10). 9_{He accepts} the apparent consequence that motion and change are never really perceived and that the apprehension of such features is a product of post-perceptual operations involving memory.

Why might someone believe the static snapshot theory? Reid evidently thought that the impossibility of apprehending phenomena such as motion without the aid of memory followed from the claim that the “operations” of the senses and perceptual consciousness are “confined to the present point of time, and there can be no succession in a point of time” (1855, Essay III, Chapter V). If we can perceptually experience a temporal structured event, our experiences of its earlier and later parts must somehow be unified—either at a time (as atomists and retentionalists believe) or across time (as extensionalists believe). Snapshot theorists are either doubtful that such unity is possible (as Reid seems to be) or doubtful that postulating it is necessary for explaining perceptual phenomenology (as dynamic snapshot theorists believe, as we will see). I will have more to say about these kinds of unity and whether they create explanatory difficulties for theories of perception in later chapters.

The static snapshot theory posits two restrictions on what we can perceive. First, we can perceive only how things are at a moment. But this restriction alone does not yield the full snapshot theory, because ‘how things are at a moment’ might include the instantiation of properties such as ‘is moving,’ or ‘is changing from red to green,’ or even ‘is flashing for the fifth time in a series of ten flashes.’ The static snapshot theorist denies

9_{Chuard calls this view ‘perceptual atomism,’ but his view should not be confused with Lee’s atomism,} which I discussed above.

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that these properties can be perceptually experienced, and so they need to restrict the class of perceivable properties to those that are ‘static,’ in some sense that excludes motion, change, and so on.

However, precisely stating this second restriction is not straightforward, because the notion of a ‘static’ property is unclear. If we want more than a merely extensional definition (e.g., ‘those other than motion, change and so on’) we need to say something about what members of this class of properties share that all ‘dynamic’ properties lack. For example, one might suggest that the static properties are those that can be instantiated only at an instant and whose instantiation can be wholly grounded in how things are intrinsically at that instant, considered in isolation from any other time. On this version of the snapshot theory, we perceptually experience only momentary states of affairs and what we experience is limited to how things are in those moments intrinsically, as if they existed in isolation, without a past or future. This seems to achieve the static snapshot theorist’s desired result when it comes to motion and change: something can be moving at an instant, but it moving at that instant depends on it changing positions over a larger interval that includes the instant. So, the fact that something is moving at an instant is not wholly grounded in what happens at the instant in isolation. But this definition produces undesirable results in other cases. Consider pitch. A sound’s being of a certain pitch is at least partly grounded in its frequency. Frequency is a temporal property; a sound’s having a certain frequency depends on what happens over an interval. Therefore, it seems that pitch is not a static property on this definition. But clearly, we can perceive pitch. So, the

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static snapshot theorist should not define ‘static property’ in this way, to avoid having to deny that we perceive pitch (and perhaps other properties).10

Thus, there is a significant question about how to make the static version of the snapshot theory precise and coherent. This conceptual issue has gone largely unexplored, perhaps because philosophers usually dismiss the theory on phenomenological grounds. Dainton, for example, begins his overview article on temporal consciousness with the claim that “we seem to be directly aware of change, movement, and succession across brief temporal intervals,” and argues that the snapshot theory is not in a position to explain this (2018). And Grush claims that “[n]othing is more obvious than that we can experience, via perception” temporally extended events involving motion (2007a, 1). The static snapshot theory is committed to the claim that all awareness of temporal properties involves a comparison between perception and memory and that all such awareness is the result of a post-perceptual inference (although this inference might be made ‘automatically’). But when you watch something move, your awareness of motion does not obviously seem to involve comparing your current perceptual experience with your memory of the immediate past.

Certain phenomenal contrast cases highlight the phenomenological inadequacy of the static snapshot theory. Broad, in an example much discussed in the temporal

10_{A possible response for the snapshot theorist might be to say that the only properties we can perceive} are those that seem to be instantiated wholly in virtue of what goes on at a moment considered in isolation, rather than those that actually meet that condition. One might then say that pitch appears to (but does not in fact) meet the condition. For example, Chalmers (2006) claims that perceptual qualities are ‘Edenic’: they are simple, intrinsic qualities that exist only in the content of our perceptual experiences. Perceptual experiences are only ever partially veridical, since there are no Edenic qualities in the world. So the snapshot theorist might insist that although pitch (considered as a property of external events) is a temporal property, experienced pitch is a momentary Edenic quality that does not exist outside of the contents of our experiences.

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experience literature, draws attention to the difference between seeing the second-hand of the clock move and seeing that the hour-hand has moved (1923, 351). Clearly, these experiences are phenomenologically different. Seeing that the hour hand has moved seems to involve comparing the seen location of the hand with a remembered, previous location, while seeing the second-hand move does not obviously involve any such comparison—it seems that you simply see the motion. The static snapshot theory conceives of all motion awareness as involving a comparison between the contents of one’s current perceptual experience with those of memory. Therefore, it does not seem capable of explaining the phenomenal contrast.

The static snapshot theorist has only three possible responses to such a case, and none looks promising. First, they might dig in their heels and insist that there is no phenomenal contrast to explain. But it seems impossible to deny that there is some

difference between the two experiences. Second, they could try to explain the difference in terms of the static properties perceived. By analogy, we might say that we can see motion in a static photograph when certain objects are blurred because of their motion during exposure. One might suggest that in Broad’s example, we immediately infer motion in one case but not the other on the basis of certain static cues, like blur. But it seems doubtful that such cues exist in all cases of motion experience (indeed, it’s far from obvious that the second hand appears blurred as it moves). The experience of inferring motion from static cues like blur in a photograph is presumably phenomenologically different from that of seeing things move.11_{Moreover, it is plausible that nonhuman}

11_{A similar suggestion comes from Koch (cited in Dainton 2018): “Your subjective life could be a ceaseless} sequence of such frames…. Within one such moment, the perception of brightness, colour, depth and motion would be constant. Think of motion painted onto each snapshot…” (2004, 264). Dainton rightly

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animals have experiences of motion of the same kind as we do without having sophisticated capacities for making inferences based on static cues (see, e.g., Bååth et al. 2014).

Finally, they could try to explain the difference in terms of non-perceptual phenomenology. But it seems unlikely that a non-perceptual difference could explain the phenomenal difference, since in both cases the subject judges that the hand is moving and

remembers its previous position. One might respond that the difference consists in the occurrence of a mental representation of motion that is not perceptual but is not a judgment either. Like perceptual experiences, this mental representation would occur automatically, and independently of what the subject judges or believes about what’s moving. Thus, the strategy would be to postulate a kind of representational state that shares certain characteristics with perceptual experiences, but to insist that it is non-perceptual. According to this view, one has perceptual experiences, understood as a series of snapshots, and then has ‘higher-order,’ non-perceptual mental states that represent the changes between snapshots.

The challenge for this response is to give a principled reason for calling this kind of representation ‘non-perceptual.’ If these states are informationally encapsulated from judgment and belief, they occur effortlessly and automatically, and they contribute to explaining seemingly phenomenological differences between perceptual experiences, then on what basis should we deny that they are perceptual? Absent an independent argument, the claim seems ad hoc. If someone were to insist that such mental states are non-perceptual, then it seems to me that we are having a merely terminological dispute.

criticizes this view as not taking seriously enough the phenomenological difference between viewing motion and viewing an image that suggests motion.

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Another, more general problem with all three responses is that, as Dainton and Grush emphasize in the quotations above, the phenomenological evidence for the claim that we perceive motion does not seem to be significantly less compelling than that for the claim that we perceive, e.g., shape or colour. Chuard writes that the snapshot theorist should insist that we mistakenly think of our awareness of temporal properties as perceptual rather than post-perceptual because of “cognitive, mnemonic, and introspective limitations of various sorts” (2011, 11). The insistence that we can be mistaken about perceptual phenomenology is reasonable. But it does not give us any reason for doubting our phenomenological judgments about temporal properties in particular.

1.3 The Dynamic Snapshot Theory: Motion and Change in Position

Earlier proponents and critics of the snapshot theory agree on a conditional claim: if perception presents only momentary states of affairs, then the perception of motion and change is impossible. In the recent literature on temporal experience, however, several philosophers have denied this conditional. They argue that perception presents us with momentary snapshots of the world, but these snapshots can portray motion and change. The dynamic snapshot theory says that while, strictly speaking, we never perceive an object as occupying different positions at different times, we can perceive it as moving in such-and-such a direction at such-and-such a rate at a time. Prosser draws an analogy between perceiving motion and representing speed with a speedometer:

… note that the position of a speedometer needle, at any time t, could itself be regarded as a representation of the speed of the car at t. It represents a rate of

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motion of the car at an instant. There is such a quantity as the velocity of an object at a time, even if motion necessarily takes time. Consequently there is no obvious reason why an instantaneous velocity could not be represented, or experienced, as part of an instantaneous content. (2016, 121)

The claim here is not simply that a static mental image can represent how things unfold over an interval of time, akin to how a motion-blurred photograph of an object can represent the object’s trajectory over an interval. Nor is it the claim that motion can actually occur at a moment, such that it can be true that an object moved between locations instantaneously. Rather, the claim is that there is such a property as movingat a time, and that it can be part of what is presented in a perceptual snapshot. Thus, if the dynamic snapshot theory is a viable view, we do not need to suppose that we perceive temporal structure to explain the perceptual experience of motion.

Dynamic snapshot theorists want to show that their theory can explain all there is to explain about perception’s temporal phenomenology, and so we do not need to suppose that we perceive temporal structure. The argument involves two stages. The first stage is to show that the idea of dynamic snapshots can explain the phenomenology of motion experience. To this end, they attempt to show that the experience of motion can be dissociated from the experience of change in position. Since motion experience does not require the experience of change in position, it does not require the experience of temporal structure. The second stage is to argue that this strategy for explaining motion experience can be extended, without loss of plausibility, to all other forms of temporal experience.

I will argue that the first stage of the argument can be seen as a limited success, insofar as dynamic snapshot theorists have presented empirical evidence that makes the dissociation between experiences of motion and those of change in position (a

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dissociation their view requires) seem plausible. However, this is not to say that the evidence offered provides any positive support for their view—and I will argue that the evidence does not help establish that their view offers a better explanation for motion experience than does the view that we experience temporal structure.

Then, I will argue that the second stage is unsuccessful. There are genuine perceptual experiences of temporal features that are not plausible candidates for the dynamic snapshot theorist’s strategy for explaining motion experience. The idea of dynamic snapshots is reasonable but inconclusive as a conjecture about motion experience; it is hopeless as an account of other aspects of temporal experience.

First, let’s consider the case of motion. Prosser (2016, 2017) and Arstila (2018) both argue that the experience of motion and the experience of changes of position are dissociable. The main case for the dissociation comes from motion aftereffects, which occur when the visual system adapts to a pattern moving in one direction and afterwards a static pattern appears to move in an opposite direction. The most famous example is the

waterfall illusion, in which watching the downward motion of the waterfall makes the surrounding rocks appear to be moving upwards.12_{Prosser describes the experience as} one in which motion in a particular direction is experienced but “arguably—it does not appear to the subject that there is any change in the locations of the objects in the perceived scene” (2016, 123). Arstila claims that the rocks appear paradoxically “to move and not move at the same time” (2018, 290).

12_{A version of the illusion is discussed by Aristotle in}_{On Dreams}_{: “And also when persons turn away from} looking at objects in motion, e.g. rivers, and especially those which flow very rapidly, they find that the visual stimulations still present themselves, for the things really at rest are then seen moving…” (Part 2).

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Arstila interprets the illusion as demonstrating that the perceptual awareness of motion involves a kind of encapsulated perceptual system dedicated to the detection of what he calls ‘pure’ motion—that is, a system dedicated to producing representations of motion without representations of differences in position. What this means is that the information accessible to and employed by the system is not available to other perceptual or cognitive systems. Thus, the detection system for pure motion might involve neurons that are sensitive to such properties as an object first occupying location l1 and then l2, but

this information is not part of the output of the system, and it is not accessible to other systems. The output of the system is the information that something is moving (with a certain direction and velocity) but not the information that it occupied l1 and l2 at different

times. The system produces experiences of motion without concurrent experiences of things being different at different times.13_{Arstila’s view is that the outputs of the system} are conscious representations of instantaneous states of the environment that include pure motion properties. The dynamic snapshot theory of motion experience is the view that all perceptual experiences of motion are of pure motion, and never of change in position.

Let us grant that motion aftereffects help to establish how the dynamic snapshot theory might work as an explanation of motion phenomenology. But do they show that the theory is the best explanation? I think not, for at least three reasons.14_{First, it is one} thing to claim that there is a perceptual mechanism that produces representations of pure

13_{Arstila is significantly influenced by Le Poidevin’s (2007) discussion of the waterfall illusion. Le Poidevin} proposes that the waterfall illusion demonstrates that there are two mechanisms for motion detection involved in perception: one that detects pure motion and another, involving short-term memory, that detects differences in position. He claims that in the illusion, only the pure motion system is activated. 14_{See Shardlow (2019) for related criticisms.}

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motion. It is quite another to claim that the mechanism produces representations of

instantaneous states of affairs involving pure motion. Even if motion is represented by a separate system, it may be that pure motion, like change in position, can be represented as being instantiated only over an interval. Evidence for a pure motion detection system thus is not by itself evidence for the dynamic snapshot theory.

Second, it is unclear what the dissociation between motion and change in position experiences demonstrated in motion aftereffects implies about ordinary, non-illusory experiences of motion. Arstila and Prosser conclude that all perceptual experiences of motion are experiences of pure motion, and never experiences of differences in position.15 But this does not follow from the evidence for a dissociation. It could be that Arstila’s encapsulated pure motion system constitutes only one aspect of the ordinary perceptual experience of motion, and that ordinary perceptual experiences of motion are also experiences of changes in position. The proponent of perceived temporal structure can argue that the experience of motion aftereffects is phenomenologically impoverished and unlike ordinary experiences of motion in this respect. Indeed, all parties seem to agree that there is something strange about your experience of the waterfall illusion. The proponent of perceiving temporal structure can explain this in terms of one of the aspects of ordinary perceptual experiences of motion being absent, while the dynamic snapshot theorist cannot.16

15_{An important caveat in Prosser’s case is that he ultimately does not think that the snapshot model (which} he calls the ‘cinematic’ model) differs in content from the retentionalist, atomist or extensionalist models (2016, 154-158; 2017, 152-154). He is influenced by Dennett’s argument that there are no empirically detectable differences between such models, and that they differ only in hypothetical distributions of ‘qualia’. I criticize Dennett’s argument in Chapter 2.

16_{This might help to explain why some commentators describe the experience of the waterfall illusion in} such quasi-paradoxical terms as something visually appearing both as moving and as staying still. For

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Third, the evidence for a complete dissociation between motion and change-in-position perception is somewhat murky. Arstila’s idea of an encapsulated pure motion detector follows the once dominant view in the psychological literature that motion aftereffects show that object position and object motion are processed completely independently. But more recent studies show a view this strong to be implausible. For example, Nishida and Johnston (1999) found that motion aftereffects do involve a shift in perceived position. In their experiment, subjects adapt to a rotating stimulus and then are shown to misperceive a static pattern as rotating in the opposite direction (this is the motion aftereffect). But they found that subjects also perceive the static pattern as displaced in orientation in the same direction as the illusory rotation—so an illusion of change in position does accompany the illusion of motion. Although these results show that Arstila’s pure motion system is not strictly encapsulatedfrom systems representing position, they do not show that these systems are identical. Nishida and Johnston argue that the motion and position systems must be distinct because the motion aftereffect and the shift in position evolve differently over time: the aftereffect decreases as the position shift increases, and the position shift can outlast the aftereffect (1999, 611). Therefore, the dynamic snapshot theorists appear to be correct that the representation of motion is not carried out by the same perceptual mechanisms as the representation of position. However, it is one thing to claim that motion experiences do not reduce to experiences of change in position and another thing to claim that one can perceptually experience motion at an instant without experiencing anything as changing position. The latter claim appears empirically unfounded.

example, Crane (1988) takes the waterfall illusion to involve contradictory representational content in visual experience (the experience represents something both as moving and as not moving).

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1.4 The Dynamic Snapshot Theory: Other Temporal Features

So far, I have argued that the first stage in the dynamic snapshot theorist’s argument for the possibility of their view is successful, although their view fares no better with respect to the available evidence than the view that we experience temporal structure. Here, I will argue that the second stage in their argument fails: the strategy they employ to explain motion experience cannot be extended to the full range of temporal features that we perceptually experience. I will do this by considering some examples. But first I will make some comments about how to understand the strategy.

Let’s call this general strategy (abstracted from its application to the motion case) the pure temporal properties strategy. In its general form, the strategy is to claim that for every variety of perceptual temporal experience we enjoy (e.g., motion experience, change experience) there is some pure temporal property P such that the temporal phenomenal character of experiences of that kind can be exhaustively explained by appealing to awareness of P. A pure temporal property is, approximately, a property that can be experienced as being instantiated at an instant.17_{Often we can specify these} properties by adding ‘at a time’ to the name of an ordinary temporal property (or, more precisely, to the present progressive form of the corresponding verb). The pure temporal property corresponding to motion is moving at a time; that corresponding to change is

changing at a time.

17_{It should also be a property corresponding to a variety of}_temporal_{experience (motion experience, change} experience, etc.), since, e.g., colours can be experienced as instantiated at an instant but are not pure temporal properties.

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This approximate definition of ‘pure temporal properties’ is useful but not quite sufficient. This is because (perhaps depending on one’s ontology of properties) there are properties that can be represented as being instantiated at an instant but that are not ‘pure’ in a sense that would be helpful to the dynamic snapshot theorist. Consider the property of occurring three seconds after a flash. A clap of thunder might have this property, and can be represented as having it at a time in speech or thought. But one cannot represent the thunder clap as having that property at a time without tacitly representing how things were at other times (in particular, how things were three seconds earlier) and tacitly representing a temporal relation between events. Thus, if such a property counted as pure, then sometimes representing pure temporal properties would involve tacitly representing temporal structure, and so the pure temporal properties strategy would not support the dynamic snapshot theory. What this shows is that the pure temporal properties involved in the dynamic snapshot theorist’s strategy are not merely those properties that can be represented as instantiated at an instant, but rather those that can be so represented without representing how things are at other times.

For any putative example of a kind of temporal perceptual experience, the dynamic snapshot theorist has two options: employ the pure temporal properties strategy to explain the experience, or deny that the experience in question really occurs (or really is perceptual). In certain cases beyond motion experience, the extension of the pure temporal properties strategy looks promising. For example, consider the experience of a continuous change such as a light gradually changing from bright to dim. This appears to be a temporal experience, as it seems to concern which properties the light has at different times. But the dynamic snapshot theorist can maintain that the phenomenology can be explained by postulating awareness of a pure temporal property—namely, that of changing in brightness from brighter to dimmer at such and such a rate at a time (Prosser

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2016, 123). At each moment you watch the light, you experience it as instantiating certain static properties (like shape and current level of illumination), as well as a certain dynamic property that is pure (the property of changing in brightness at a certain rate). You do not, according to this explanation, ever experience the light as having changed from one level of brightness to another, or as being at one level of brightness at t1 and

being at a different level at t2. Thus, this case seems to be well-suited to the pure temporal

properties strategy.

Other cases look less promising for the strategy. Consider the experience of succession: of one event as following another. Here, the dynamic snapshot theorist cannot employ the strategy, because no pure temporal property is available that would explain the phenomenology. They cannot say that we perceptually experience the second event as instantaneously instantiating the ‘pure’ temporal property of following the first, because this would be to admit that we perceive temporal structure. Here, they are better off trying to deny that experiences of temporal order are genuinely perceptual and maintain that awareness of succession is always a post-perceptual achievement involving memory.18

The strongest evidence against the dynamic snapshot theory would be a case where neither of these responses is plausible. One kind of case that fits this description is a certain kind of experience of the persistence of an object across time. To illustrate the kind of experience I have in mind, consider the motion-bounce illusion (Sekuler et al. 1997). The illusion involves an ambiguous percept in which two dots approach each other and

18_{Arstila suggests employing the pure temporal properties strategy across a range of cases, including the} perception of change, causation and succession (2018, 9-10). For the reasons I have discussed, I do not think that the strategy is available in the case of succession.

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can either be seen as crossing paths or as bouncing off each other and changing trajectories. Subjects might interpret the visual percept on its own as either ‘bouncing’ or ‘passing,’ but the ‘bounce’ interpretation can be induced by inserting an audio cue at the moment the dots meet. There is an obvious phenomenological difference between the experiences associated with the ‘bounce’ interpretation and the ‘pass’ interpretation. The difference seems to concern which dot is which, before and after they intersect, and whether or not the dots change trajectories. But it is unclear what the dynamic snapshot theorist could say about this phenomenological difference, because which dot is which doesn’t seem to be a matter of how things are at any time considered in isolation. At each moment you are watching the display, you will see two dots as having the same static properties (like location) and the same pure temporal properties (like instantaneous rates and directions of motion), regardless of whether you see them as bouncing or passing. Rather, the difference between interpretations seems to concern what’s going on across time: whether the dots appear to change direction at the moment they intersect, and whether the dot that was in the top-left quadrant of the display is now in the bottom-left, or in the bottom-right.

The dynamic snapshot theorist might reply that the characterization of the difference as a temporal difference is incorrect and that instead we just experience each dot at each time as instantiating an identity-involving property. For example, we first experience the dot in the top-left quadrant as having the property of beingdot A. Then, in the bounce interpretation, we experience the dot in the bottom-left quadrant as having the property of being dot A, and in the pass interpretation, we experience the bottom-right dot as having that property. According to this reply, the property of being dot A is not a temporal property. Thus, there is a difference in the experience associated with each condition that is not a difference in how things are experienced as persisting over time.

Perceiving Temporal Structure

Perceiving Temporal Structure

Perceiving Temporal Structure

Abstract

Acknowledgements

Table of Contents

Introduction

Chapter 1

Do We Perceive Temporal Structure?