# Hearing Objects and Events Nick Young ## Abstract Through hearing we learn about source events: events in which objects move or interact so that they vibrate and produce sound waves, such as when they roll, collide, or scrape together. It is often claimed that we do not simply hear sounds and infer what event caused them, but hear source events themselves, through hearing sounds. Here I investigate how the idea that we hear source events should be understood, with a focus on how hearing an event relates to hearing the objects involved in that event. I argue that whereas we see events such as rollings and collisions by seeing objects move through space, this cannot be how we hear them, and go on to examine two other possible models. On the first, we hear events but not their participant objects. On the second, to hear an event is to hear the appearance of an object to change. I argue that neither is satisfactory and endorse a third option: to hear a source event is to hear an object as extending through time. ## 1 Hearing the Sources of Sounds Hallucinations notwithstanding, we have auditory experiences when sound waves hit our eardrums. Sound waves are usually produced when material objects[^1] move or interact so that they vibrate, such as when they are rolled, scraped, struck, or smashed. Such events are referred to as sound sources, or source events. We very often learn what sort of source event is taking place just from what we hear: if you close your eyes and I roll a bowling ball across the floor you will learn that a heavy, hard, round, object is rolling, if I drop it you will learn that that an object with those same properties has collided with something. A majority of contemporary philosophers who work on auditory perception think that our awareness of these events is due to our hearing these events. The aim of this paper is to determine how we should understand such a notion. What is it to hear a source event? The idea that we hear sources at all might strike some as odd. Do we not hear the sounds that these events produce, rather than the events themselves: the rumble of the rolling and the clunk of the collision? If sounds are all we hear then this would mean that our awareness of everyday events is indirect: we hear the rumble and infer the rolling in the same way that we might hear the rumble and infer that the bowling alley is open, or see smoke and infer fire. While this idea has some historical precedent, Berkeley claimed "in truth and strictness, nothing can be heard but sound" (1713/2012, p. 67), it is a very unpopular amongst contemporary philosophers interested in auditory perception.[^2] O'Callaghan says that, sources "meet causal requirements on auditory perception, and it would be severe to deny they belong among what it seems to us we hear" (2011, p. 1), Kulvicki is concerned that if sounds are understood as individuals distinct from material things, we risk putting "events of interest" (that is, source events) at "one remove" from listeners (2008, p. 15), while Leddington argues that a phenomenological intimacy between listener and source event is apparent in auditory experience: it does not seem as though we are hearing signals or signs of source events, but rather the events themselves (2014, pp. 328--329). Many accounts of auditory perception avoid the severity of Berkeley's view by tethering the hearing of sources to the hearing of sounds. One way of doing this is to say that we hear sounds as properties, either of objects that participate in source events (e.g. Kulvicki 2008) or the source events themselves (Leddington 2014). On this sort of approach, we, as Leddington puts it, hear sources in hearing sounds (ibid., p. 324). Another is to say that sounds are individuals distinct from sources but that we hear sources mediately, through or by hearing sounds. O'Callaghan, for example, proposes that we hear sounds as parts of events (2011), and Nudds that we hear sounds as having been produced by sources of one kind or another (2010, p. 285). My interest here is not in what sounds are, nor in the relation between sound hearing and source hearing, but in source perception itself. All the views just mentioned are united in saying that sources are heard, not inferred, and I want to explore what such a claim amounts to. Questions about source hearing can be decoupled, by and large, from questions about sound hearing: claiming that we hear a source as causing, as part of, or as bearing, a sound, does not explain what it is to hear a source, in the same way that seeing an object as a cause, as having other objects as parts, or as bearing a colour, does not explain what it is to see an object. You and I might agree on how sound hearing relates to source hearing, yet disagree about what sounds are, conversely, you and I might agree on what sounds are, and on how hearing them relates to hearing sources, yet disagree about how the second relatum should be characterised, about what hearing a source consists in. For these reasons, sounds will feature little in what follows, with the focus instead being on how source hearing should be understood in and of itself. [^1]: Sound waves can of course also be produced by the movement of liquids or gases. Although I will talk only about material objects here, everything I say applies mutatis mutandis in these cases as well. [^2]: In contemporary philosophy of perception, Matthen comes closest to a sounds only view of audition: "objects are characterizable by the sound they make---there are squeaky violins, baritone singers, alto saxophones---but the inferential path from auditory experience to such dispositional characterizations is quite indirect" (2005, p. 285). Martin says: "One may pick out the source of the sound via picking out the sound itself---we might then understand the demonstrative expression, 'that dog' as involving deferred ostension, perhaps as the descriptive phrase, 'the dog which is actually the source of this sound'" (1997, p. 93) but has a less hardline view in his later work, saying that, in some cases at least, source events can be heard (2012, p. 348). ## 2 Seeing and Hearing Events ### 2.1 What Is Heard? Although the claim that we hear source events is popular, I shall argue in this section that it is not obvious how it should be understood. This can be brought out through a comparison with vision: while we have a clear idea of what it is to see events, it is implausible to think that we hear events in the same way. If this is correct, we must characterise source hearing in some other way. We can begin by asking what is heard when we hear source events. It is common in contemporary philosophy of perception to think that our perceptual systems supply information about features of the immediate environment. As Matthen puts it, perception is "outward-oriented", in that it "conveys... a message about the external world" (Matthen, 2005, pp. 3--4).[^3] If this is correct, we can ask what types of feature a given perceptual modality is oriented towards. The mainstream view for vision, for example, is that we receive messages about material objects, the medium-sized dry goods which surround us (e.g. Cohen 2004; Nanay 2013, p. 51; Matthen 2005, pp. 277--282).[^4] [^5] They are what is seen in the first instance, meaning that anything else we see, we see by seeing them and their properties. Disagreements as to what sounds are can be understood as a debate about whether the auditory system is oriented towards one feature of the environment or another: does hearing a sound consist in the auditory system picking out sound waves (Nudds 2010), disturbances of a medium (O'Callaghan 2007) or properties of objects (Kulvicki 2008)? If, as I have suggested, questions about source perception can be considered separately from questions about sound perception we can ask what aspects of the environment are picked out when we hear source events. One might think that in asking this question we have answered it: we are auditorily oriented towards events. Whereas the visual system deals in balls, doors, and vases, the auditory system keeps track of rollings, slammings, and smashings. Things, however, cannot be so straightforward, as source events include material objects: there is no such thing as a rolling (or collision, scraping etc.) simpliciter, something needs to be doing the rolling. Given this complication, is it possible to make sense of the idea that events and not objects are fundamentally what is heard? Can we hear a rolling without hearing that which rolls? We shall see later that there are those who argue that we can. Alternatively, perhaps audition, like vision, picks out material objects, and that "hearing a rolling" is just an elliptical way of saying "hearing a ball". But questions can be asked of this approach too. How does hearing a material object differ from seeing it? How should we characterise the difference between different types of events involving the same object, such a ball rolling and a ball bouncing? In vision the relation between object seeing and event seeing is straightforward. If material things are what we see in the first instance, then we see events by seeing objects: seeing a rolling consists in seeing a ball and seeing it to move, to change its location and orientation. Seeing different types of event consists in seeing the object move in different ways: the ball rolls horizontally across the ground, and falls vertically towards the ground. Might we hear events in the same way? That is, does source perception consist in the auditory system picking out objects and hearing them to change location? We might already be suspicious that this is the correct way to characterise source hearing, but it will be instructive to bring out exactly why. I suggest that we cannot hear events in the same way that we see them because seeing movement depends upon a certain structural feature of vision, the spatial field, which audition does not share. [^3]: This is in contrast to the sense-data theories of perception popular in the first half of the twentieth Century. [^4]: Representationalists such as Cohen, Nanay, and Matthen hold that perceivers represent material objects and attribute, or predicate, properties to them, but relationalists also think that material objects are, fundamentally, what we see, in that perception consists in their standing in a certain type of relation to a subject. See, for example, Brewer (2007). [^5]: Less mainstream views of vision can be found in Clark (2000) who argues that we see, first and foremost, places, portions of space, not the things which occupy them. And Matthen (2010) who suggests that we see two types of individual simultaneously: material objects, and the ambient light illuminating those objects. ### 2.2 Perceiving Movement and the Spatial Field When our eyes are open we are not presented simply with material objects and their properties, but rather a portion of space with some regions filled by objects, and some empty regions that could potentially be filled by objects, this feature of visual experience I will refer to (following for example, Martin 1992; Richardson 2014) as the spatial field. Taking in a region of space at a time adds to visual experience in various ways. First, it allows for the perception of spatial relations between different objects: you see the bowling ball as in front and to the right of the region of your feet. Second, it allows for the perception of property variation: you can see your bowling shoes gradually change from a bright green at the toe, to a darker shade at the heel.[^6] Third, it allows for the perception of the precise location of objects, in that objects can be seen to extend across, or fill out, certain regions of space: seeing the bowling ball to be located here rather that there is to see it to fill out this ball-shaped region of space rather than that one. It is this final aspect of spatial seeing which allow us to see movement. Watching an object move involves seeing it to extend over different portions of space at different moments: seeing the bowling ball roll down the lane involves seeing it to be first by your feet, then increasingly further away as it travels down the lane.[^7] Audition however, is not field-like in the same way that vision is. It does not present an array of filled and empty regions of space, nor of objects as extending through space. As O'Callaghan puts it: > It is counterintuitive to say you can auditorily single out material objects because auditory experiences do not reveal three-dimensional solid bodies with rich internal spatial structure as such. (2011, p. 23) This is not to say that audition provides no spatial information. We often hear source events as located: footsteps behind us, a ball colliding with the ground to the left. We can also hear source events to be at different locations from moment to moment: the rolling is heard to be close by and then increasingly further away as the ball travels down the lane. However, hearing source events as located is not equivalent to hearing clearly bounded, three-dimensional objects. We do not hear the shape of the rolling ball, where its stops and the rest of the world begins. Consider a different case: you lie in bed while a mosquito flies around your head, and from what you hear you learn that it is first on the left and then the right. But this is still quite dissimilar to how we would see the creature move. First, as with the bowling ball case, our experience is not of a three dimensional, mosquito-shaped object extending over different portions of space. Second, the source event in this case, the movement which produces sound waves, is not the mosquito flying from the left to the right per se, but rather the beating of its wings, and we do not hear this event by hearing each wing to fill out different wing shaped regions of space at different moments. In both of these cases, it seems that while the approximate location of moving objects is revealed by hearing the location of the source event in which they participate, we do not hear source events by hearing these objects to extend over different regions of space at different moments.[^8] Finally, notice that, unlike vision, auditory experiences can sometimes lack spatial information entirely, yet our ability to recognise events is not impeded. If a mono recording of a rolling ball is played back on headphones it will still be identifiable as a rolling, yet it will present the listener with no information as to which direction the object is travelling. There is no visual equivalent of such a case.[^9] If hearing movement cannot be modelled on seeing it, we need a different account of source perception. I shall now examine two suggestions as to what this might be. On the first, we can hear source events but not the objects participating in those events. On the second, hearing sources is conceived of as analogous to seeing the appearances of objects to change. I shall argue that neither approach is satisfactory and go on in Sect. 5 to put forward my own account. [^6]: Property variation will be returned to later when change perception is discussed. [^7]: We will see later that there is more to seeing movement than this. [^8]: The degree to which audition provides spatial information is controversial See, for example, Strawson (1959, pp. 65--66) Casati and Dokic (2009). [^9]: At least, no non-pathological equivalent. Patients suffering from simultanagnosia (a symptom of Balint's syndrome) can perceive only one object at a time and are unable to locate that object in relation to others. It is possible that if a sufferer of simultanagnosia were able to track an object as it moves (those with this condition also have difficulty fixating on moving objects) they would perceive an object moving, but not see where it was moving from or to (see Rafal 1997, 2003). Thanks to an anonymous referee for drawing my attention to these cases. ## 3 Not Hearing Objects O'Callaghan suggests that the fact we do not hear material objects as extended in space is a reason to give up the idea that we hear material objects at all. He says: "Plausibly, perceiving a particular thing requires being able to differentiate, discriminate, or distinguish it from the surrounding environment" (2011, p. 8), and points to similar claims that have been made about vision, such as Siegel saying: "If S sees o, then S's visual phenomenology differentiates o from its immediate surroundings" (2009, p. 434).[^10] He suggests instead that "Hearing is notable in that...you do not auditorily experience ordinary material objects as such, while you do auditorily experience their activities" (2011, p. 23) and goes on to suggest that an advantage of his own account of source perception is that it allows for "the evidential parity of vision and audition regarding, respectively, material things and their activities" (ibid., p. 26). A similar idea can be found in Casati et al.: > The immediate object of auditory perception is just the event that is the sound...in virtue of the perception of it we may recognize the thing source. "In virtue of" means, roughly, that one has indirect awareness of x when one's awareness of x is caused by one's awareness of something else (2013, p. 465; see also Leddington 2014, p. 330) This type of approach reverses the order of priority that we find in vision: we do not see events, but only objects moving or changing; we do not hear objects, but only events unfolding. While the idea that vision deals with objects and audition with events has a certain neatness, I think objectless accounts can be challenged in three ways: a lack of spatial singling out is not a good reason to give up the idea that we hear material objects, the idea that we hear source events but not their participating objects raises more questions than it answers, and we can ask whether an account of source perception which discards material objects is even desirable. First, while it may be that spatially singling something out is a necessary condition for seeing it, making a similar requirement for audition would seem to preclude the hearing of just about anything. As we have seen, although audition is spatial, it is not field-like in the way that vision is; whatever we hear, we do not hear as filling regions of space. Source events are not auditorily singled out: we might hear the rolling to be over there, rather than over there, but we do not differentiate it from its surroundings or hear it as shaped. If this is correct, why should we think event individuals are a better candidate for what is heard than material objects? Neither, if they are understood as individuals distinct from source events, it is plausible to think that we spatially single out sounds. Consider O'Callaghan's own proposal as to what sounds are: > sounds are the events in which a medium is disturbed or changed or set into motion in a wave-like way by the motions of bodies. Events such as collisions and vibrations of objects cause the sound events. (2010, p. 36) On this account, sounds extend in space: there are portions of the environment in which the air (or some other medium such as liquid) is disturbed by the motions of bodies, and portions where it is not, but we do not hear them to extend over space in this way, we do not hear where they end and the rest of the world begins. It might be objected here that sounds, unlike objects, have fuzzy boundaries, as air will be disturbed less and less the further away it is from the vibrating object, but this is beside the point; we do not hear individuals with fuzzy boundaries, as we might see a cloud of smoke to fade at its edges, instead audition presents no information about boundaries at all. Again, this should not be taken as the claim that audition is non-spatial: we hear what we hear to be located, but we do not hear things as located in the same way that we see them to be. In short, a lack of spatial singling out can be understood as a characteristic way in which audition presents whichever features of the world it presents, not as evidence that it presents one type of individual or another. If this is correct then material objects have no less a claim of being heard than anything else. [^10]: He also cites Strawson (1959), Dretske (1969, p. 20), Martin (2007, p. 706). Second, this approach to source hearing offers a muddy answer to the question of what we hear when we hear sources. We have already seen in Sect. 2 the difficulties in making sense of the idea that we hear source events but not the objects participating in those events. How can we hear a rolling without hearing that which rolls? Moreover, unless they are willing to give up outward orientation, defenders of this position are required to say which aspects of the physical environment are auditorily picked out in source hearing if not material objects. It cannot be the air that moving objects disturb, as this would be to hear sounds produced by sources rather than sources themselves, but there appear to be a dearth of other candidates. What other aspect of the physical environment could be picked out by our auditory systems and still be properly considered a source event? Discarding objects also causes problems in accounting for the audible similarities between different source events involving the same object. Consider, vision: the experience of seeing a ball dropped on the ground, and seeing it roll along the ground have something in common. Specifically, obviously, we see the ball in both cases. Consider audition: if I drop the hard, heavy, bowling ball on the ground, and then roll it towards you, the auditory experiences each event elicits have, arguably, something in common. You can tell, just through hearing, that it is the same object, or at least an object with the same properties, taking part in both events. But if the audible similarity between these cases cannot be explained in terms of them sharing objects, how can it? Problems remain even if a slightly weaker version of the position is adopted. Elsewhere in his (2013) O'Callaghan considers the possibility that we in fact do hear objects, but only derivatively, as "constituents", "protagonists", or "sufferers" of source events (p. 23). However, it is again not obvious how such an idea should be understood.[^11] While it is straightforward to explain how we see events by seeing objects---seeing an event is to see an object move or change---it is much less clear how to make sense of the idea that we hear events first and foremost, and through doing so hear their protagonists. Third, it is questionable whether we would want an account of source hearing which excludes material objects. Recall the reasons mentioned in Sect. 1 for wanting an account of audition which allows for source perception: to not do so would be "severe" (O'Callaghan 2011, p. 1), put interesting events at "one remove" from the listener (Kulvicki 2008, p. 15), and conflict with the "phenomenological intimacy" apparent in auditory perception (Leddington 2014, pp. 328--329). However, excluding material objects from what we hear is, arguably, quite severe, as our interest in source events is not only in the type of event taking place (a rolling, collision etc.), but also in which objects are participating (what is rolling, colliding etc.): we are interested in the smashing because it is the smashing of an expensive vase, or our kitchen window. Neither is it obvious that we are any less auditorily intimate with the objects than with their activities: we learn immediately from what we hear that a rolling is taking place, but we become aware, no less immediately, that it is a heavy, round, object doing the rolling. Excluding objects from what we hear risks throwing out the baby with the bathwater. [^11]: I am also uncertain how such a claim can be reconciled with O'Callaghan's stronger claims quoted at the beginning of this section.