Phenomenology of Smells Phenomenology of Smells For Husserl, phenomenology is "the reflective study of the essence of consciousness as experienced from the first-person point of view."1 The phenomena, which are intuitively experienced, are used as starting points in phenomenological investigations. From the phenomena, phenomenologists try to extract the structure of consciousness by a systematic reflection and analysis. Merleau-Ponty writes in his preface to the Phenomenology of Perception: "Phenomenology is the study of essences: the essence of perception, or the essence of consciousness, for example."2 Most of the phenomena, perceptions, and consciousnesses that are used in phenomenological studies are visual. Husserl writes in the Analyses Concerning Passive Synthesis: "Let us privilege here the normal and basic instance of the constitution of external existence, namely, the constitution of unaltered spatial things." (p. 11)3. However, despite this declared focus on vision, both in Husserl and in Merleau-Ponty, it is clear that they are not concerned with something that could be called visual 1 David Woodruff Smith (2007) Husserl New York: Routledge Maurice Merleau-Ponty (1962) Phenomenology of Perception translated by Colin Smith, New York: Routledge 3 Edmund Husserl (2001) Analyses Concerning Passive and Active Synthesis - Lectures on Transcendental Logic translated by Anthony J. Steinbock, Dordrecht (Netherlands): Kluwer Academic Publishers All quotes from Husserl are from this book. The page numbers refer to the German edition: Edmund Husserl (1966) Analysen zur passiven Synthesis (1918-1926). Husserliana XI, ed. Margot Fleischer 2 Phenomenology of Smells phenomenology; they are interested in the essence of consciousness and the structure of all possible experience, regardless of the sensory system that probe the phenomena. The focus on vision combined with mild curiosity about hearing and touch and a disregard for smell and taste that is found in phenomenological writings has a long tradition in philosophy. In the Timaeus Plato writes that God has given us sight to give us philosophy and that we can derive philosophy from vision because it gives us the inspiration to think of rational abstract concepts. Smells, on the other hand are "a sort of half-breed" and only the terms "pleasant" and "painful" apply "to them with any clarity"4. In Kant's Critique of Pure Reason, the attempt to identify necessary structure in experience in the Analogies of Experience rests on visual examples (a ship sailing down a river, a lead ball resting on a pillow, the moon circling the earth) with one exception, the fire in the fire place causing a room to heat up5. Husserl and Merleau-Pointy follow Plato and Kant and rely on an analysis of visual experience. The occasional appearances of other modes of perception (mostly audition) in their writings are sometimes used to show that their analysis is not restricted to visual experience, whereas at other times they are used as a contrast to the visual phenomenology. Husserl explains the tripartite structure of time consciousness using both visual and auditory examples to show that they are interchangeable. On the 4 Plato's discussion of smells in the Timaeus can be found in 66D to 67B. It is noteworthy that the example of the fire and heat is less convincing than the visual examples because it remains unexplained how one could perceive the fire (perceived visually) to cause the heat (perceived through thermosensors on the skin) when there is no perceptible connection between the position in space in which the fire is experienced and the position in space (on the skin) where the heat is experienced. 5 Phenomenology of Smells other hand, Merleau-Ponty lists psychophysical experiments in support of his view that man merely "inhabits his auditory phenomena and 'lives' in the visual"6. I propose here to systematically investigate the different sensory modes phenomenologically. The results generated by reflection and analyzes of phenomena are necessarily limited by the phenomena which, as intuitive experiences, are in turn limited by the sensory organs. Adding a wider variety of phenomena to the analysis will overcome this limitation and increase our knowledge of the structure of consciousness. In as far as phenomenology attempts to describe the essential features of all possible transcendental phenomena the considering of non-visual phenomena will help to avoid the mistake of confusing features of the eye with features of consciousness. Towards this goal I propose to analyze the phenomenology of smells. Here, I will first introduce the five senses and then the sense of smell in more detail. I will then develop an ontology of smells with phenomenological topics on my mind. I plan to extend this ontology to a comprehensive phenomenology of smells later. The Five Senses Aristotle described five senses: vision, hearing, touch, smell, and taste. Today, there is no agreement on the number of senses that humans possess because there are alternative usages of the concept "sense". Humans can sense magnetic fields, pain, temperature, relative positions of joints, etc. A common modern classification that is based on the cellular properties of sensory cells recognizes four senses: 6 Footnote on page 293 of the Phenomenology of Perception Phenomenology of Smells chemoreception, photoreception, mechanoreception, and thermoception. In principal, there is nothing in the physical world that can not be sensed. Some animals for example have electroreception, etc. From a phenomenological perspective it is irrelevant if the sensation is caused by a photon or a volatile chemical and what the features of the sensory cells are. A phenomena like the flavor of food is simple and unified, although it is vastly complex at a biological and cognitive level. Flavor consists of the activation of taste cells, smell cells, the trigeminal nerve, heat-sensing cells in the mouth, and mechanosensory cells in the mouth that assess the texture of the food. These cells all project to different areas in the brain. How these signals are integrated to generate a unified phenomenon is not understood. Similarly, kinesthetic senses (also called proprioception) and other introceptive senses influence strongly the phenomena of exteroceptive sense without producing their own (conscious) phenomena7. There are differences between the senses that are relevant to phenomenology. These differences concern the temporal and spatial structure of the phenomena. Vision is spatially and temporal continuous. This is a feature of great importance.8 Causality, like in the case of a billiard ball colliding with another billiard ball, can only be perceived in a temporally continuous perception. A spatially continuous perception is necessary to perceive things as simultaneous. The philosophical importance of the continuity of 7 Perhaps surprisingly, Husserl is not a proponent of multimodal integration: "We must not think that temporal continuity can be filled with just any content: We cannot mix color data together with sound data to form a unity of an immanent temporal datum; homogeneity in continuity belongs to a selfcontained datum." (p.141) 8 Again, the Analogies of Experience in the Critique of Pure Reason nicely demonstrate the consequences of the focus on visual perception. The spatial and temporal continuity of visual perception are necessary for Kant to establish the unity of nature. Phenomenology of Smells visual perception nicely corresponds to the functional and evolutionary importance of this feature. The signal from the photoreceptors is not at all continuous. We blink. During the several dozen microsaccadic eye movements every second, the image, that would otherwise appear blurred from the motion, is suppressed by a process known as saccadic masking. The temporal resolution of the human eye is rather low. However, a very sophisticated neuronal machinery is dedicated to make our visual experience continuous. Similarly complex mechanisms are employed to establish (the illusion of) spatial continuity despite, for example, a 2mm wide hole in the retina where the optic nerve passes through the retina (the physiological blind spot). The continuous space that is perceived through vision is three-dimensional, despite the retina being a twodimensional surface. Hearing is temporally continuous like vision, but it is spatially ambiguous. Hence, Husserl's positive use of it in the context of temporality and Merleau-Ponty's negative use of it in the context of spatiality9. Auditory space is three-dimensional, despite the cochlea being a one-dimensional structure. Taste and smell are fundamentally different from vision and hearing. These two sensations are much more active. They are usually involved in the active sampling of information to assess, for example, the edibility of a food item. In taste the sampling is done by putting something in our mouth, in smell it is done by sniffing. Both create discrete sensory events. If we have a temporally continuous smell or taste experience 9 Spatial audition, auditory scene analysis, and binding of sound features across space are very complex problems that can not be discussed here further. I only wish to make the point that there is some spatial perception in audition but that it is more ambiguous than in vision. Phenomenology of Smells this is unusual and unsettling (having a taste in your mouth, having a smell stuck in your nose). Again, the phenomenological importance of the temporal discreetness of these phenomena is reflected by the functional importance and the extensiveness of the processes involved in achieving the discreetness. There is no spatial information in smell and taste experience10. Touch is in between sight and hearing on the one side and taste and smell on the other side. The special position of touch comes through the fact that it can be both active and passive. We can sense that we touch something (in which case touch is similar to smell and taste) or we can sense that we are touched by something (in which case touch is similar to vision and hearing). This dualism of touch is the tactile description of the dual structure of the body as object and subject. Its importance for existential phenomenology is discussed by Sartre in Being and Nothingness. The similarities between the chemical senses (taste and smell) and active touch extend to the temporal structure. When we probe something with our fingers to gather information, this is done in discrete movements in which different constellations of the fingers are employed11. Passive touch is temporally continuous. Active touch senses a three dimensional space. A hand touching a pen on the desk analysis this scene in three 10 In artificial experimental situations tastes can be applied to discreet areas of the tongue and subjects can learn to recognize which area of the tongue is tasting (much like locating a touch on the bodies surface). This shows that it is possible to have taste phenomena with a spatial component. However, in normal experience this does not happen. For smells, there is no spatial structure to the phenomena at any given moment (as opposed to vision and audition), but over several sniffs and under the involvement of body movements, smells can be given a spatial structure. This is discussed in detail below. 11 Spatial touch, tactile scene analysis, and binding of tactile features across space are very complex processes that I can not discuss here. The surface of a skin is a two-dimensional sensory field and if the fingers probe an object, the spatial relations of the contact points in this field are unrelated to the spatial structure that is experience. Kinesthetic senses are probably the real source of spatial information. A configuration of the fingers can be analyzed as the shape of the enclosed object even without touch perception. Phenomenology of Smells dimensions. Passive sense is two-dimensional and the dimensions are congruent with the sensory field (the skin). Smell The most interesting modality to analyze phenomenological as an addition to the extensive analysis of vision is olfaction. As described above, vision and audition are similar. Taste and smell are similar to each other but very different from vision. Touch is in between the two extremes. An analysis of vision and smell will therefore cover the whole spectrum of possible phenomenomenal experience. It is noteworthy that smell used to play a much more important role in the life of humans until very recently. Before artificial lightning was common, vision was of limited use. It was presumably very common to encounter an object olfactory without encountering it visually or otherwise. The purely olfactory phenomena that are considered here are therefore common and relevant and not abstracted unrealistic situations12. To understand the phenomenology of smells, some neurobiological features of smell perception have to be known. Smells are volatile molecules. They are inhaled through the nose during sniffing and bind to receptor molecules on the surface of nerve cells that extend from the brain through small holes in the skull into the nasal cavity. The binding of the smell molecules induces the nerve cells to fire a signal to a brain 12 Two recommendable books that show the importance of smell information throughout history and in non-Western cultures are: Constance Claasen, David Howes, and Anthony Synnott (1994) Aroma - The Cultural History of Smell New York: Routledge, and Mark M. Smith Berkeley (2007) Sensing the Past Seeing, Hearing, Smelling, Tasting, and Touching in History Berkeley: University of California Press Phenomenology of Smells structure called the olfactory bulb. The binding of the smell molecule to the molecules on the surface of the cells is thought to be mediated by shape (the lock-key theory)13. Similarly shaped molecules bind similar receptor molecules and each smell molecule binds to many different receptor molecules. Each receptor molecule in turn binds a variety of different smell molecules. The result is called combinatorial coding: each individual smell molecule binds to a specific and unique combination of receptors. Natural smells consist of a mixture of a large number of different types of molecules. The processing of the smell information from the olfactory bulb happens in an evolutionary very old brain system that is otherwise mainly concerned with emotions, behaviors, and memories (as opposed to higher cognitive abilities mediated by the cortex and other structures). It is because of this overlap of structures involved in smell assessment and the regulation of emotions, that smells are so potent in evoking memories, emotions, aversions, etc. The brain system in which this happens is called the limbic system. Olfaction is different from all other sensory system in that the information is not relayed through the thalamus. This is relevant, because the thalamus is speculated to be involved with consciousness. After explaining my reasoning for studying phenomenology of smells and reviewing relevant biological factors about the nose, I will now come to the main part of the paper where I will sketch an ontology of smells. I will focus on six aspects that are of great importance in Husserl's visual phenomenology. 13 This theory is not uncontroversial. Phenomenology of Smells Ontology of Smells 1: Temporality The olfactory experience is not temporally continuous. It is parceled in sniffs. Within each sniff, the experience is temporally continuous but it is not constant. The intensity during a sniff changes, with few smell molecules arriving at the neurons in the nose early and late in the sniff and the bulk being delivered in the middle of the sniff. In addition to the changing intensity, the experienced smell quality also changes during a single sniff. Natural odors consist of a mixture of different types of smell molecules that are of different sizes and weights. These molecules have to diffuse through mucus to reach the nerve cells that carry the smell receptors. Because of their differences in size, the molecules take different times to travel through the mucus and arrive at slightly different times at the nerve cells. They are consequently experienced at different times. The light, diffuse top notes of a smell are perceived early (they consist of small light molecules) whereas the heavy, animalic base notes are perceived later (they consist of large heavy molecules). A sniff constitutes a smell object. The object consists of the different attributes (notes) that are stretched out over time, unlike a visual object, whose attributes are stretched out over space (like the front and the back of a cube), or overlapping in both space and time (like the color and shape of a colored figure). The sniff as a olfactory object is analogues to the auditory object, like a tune from a violin, as described by Husserl: "All continuity with respect to content (e.g., the continuity with respect to the content of a sound from s violin) is the unity of a continual fusion passing from phase to phase; but the content can only meld together continually in the continual process of becoming in the order of time." (p.141). Phenomenology of Smells The idea of the sniff as an object therefore has the consequence that, like in audition, an object has a temporal structure. Ontologically this results in a more complex situation than with visual objects. What about temporal relations of olfactory objects to each other? Clearly olfactory experience is discontinuous, parceled by sniffs. We can increase our sniffing rate, thereby increasing the number of objects per time. However, we can never reach the level that the visual system reaches when watching TV. When watching TV the picture rate is so high that the illusion of continuous motion is generated by a succession of stationary images. We can not sniff at a high enough rate to generate the illusion of a continuous, changing, "moving" olfactory world. Because of the discontinuity, memory plays a more important part in any olfactory phenomenology of time that unites more than a single sniff (object). Ontology of Smells 2: Constancy of Smell Objects We said that a smell object is smeared out over time in a single sniff. Two subsequent sniffs would therefore sample two objects. Can these be the same object? Is the smell (object) of a frozen pizza the same smell (object) as the hot pizza in the oven and the burnt pizza? The pizza as an object is the same although its visual and olfactory appearance changes. The smell object, however, does not stay the same. It is a different object. In fact, the whole purpose of having discreet odor phenomena through sniffs is to dispel the illusion of one all-encompassing and gradually changing smell object inside Phenomenology of Smells of which we live14. Two sniffs, therefore, can never reveal to us the same object, although they can reveal identical objects. This, however, is not the normal case. In the normal case the objects are different by intensity or quality15. Ontology of Smells 3: Spatiality of Smell Objects Smell Objects have no extension in space. Each sniff samples a singularity in space. When we use several sniffs and therefore several smell objects to constitute spatiality from smells, we construct a smell landscape out of smell objects. The smell landscape can be very simple. If we imagine in a wind-free environment a point source of a single smell, the landscape will consist of smell objects of decreasing intensity in concentric circles around the source. The reason why we can't think of the whole smell filled space as a smell object is that it does not have boundaries. There are just stochastic distributions of small odor molecules. To create a smell landscape, we have to move. This is in stark contrast to (for example) vision and audition, where spatiality (in the form of position) is innate in the object. With smells the position of the smell is the position of our body and we need to locate and move our body to locate smells. 14 Incidentally, our olfactory world in the womb before we are born is continuous. It is one continuously changing odor object inside of which we live. In the womb, the nose is filled with fluid and the odor molecules are transported to the olfactory epithelium by diffusion and not by sniffing. What we smell in this environment is fundamental for our future preferences. Children born to mothers who consumed anise during pregnancy for example show a stable preference for anise after birth (Human foetuses learn odours from their pregnant mother's diet Schaal B, Marlier L, Soussignan R, Chemical Senses 25(6) 729-737 (2000)). 15 The case of two subsequent sniffs producing the same odor object is only a theoretical possibility. If subjects are given the same odor sample twice (without knowing that it is the same sample) and are asked to say if the to samples are the same quality and intensity, they very often do report the two sniffs as being different. This is explained by stochastic differences in the complex air flow that is produced inside the nose by sniffing. Phenomenology of Smells Therefore, we do not only have to move, but we also have to have a kinesthetic sense of our movements to create the smell landscape16. Ontology of Smells 4: Coexistence of Smell Objects Coexistence of objects is one of the few topics were Husserl considers different modalities. He writes: "What holds for the visual filed holds for the tactile field - for all authentic fields as such that are unities of locality. Not for the auditory field; it is not an authentic field. For here we lack every possibility of ordering the coexistent." (p. 137). While the auditory filed is not an authentic field, the olfactory "field" is no field at all. But is Husserl's intuition that only a field will allow to order the coexistent correct? Can smell objects coexist in time? Each sniff constitutes an object and we can not perform two sniffs simultaneously. The question of the coexistence of smell objects is a question of identifying smells and therefore ultimately of language. The complexity of an odor (in physical terms) is the number of different types of molecules it consists of. A rose has a complex odor consisting of over 300 different types of molecules. The odor of leaking gas in contrast consists of only a single type of molecule that was added to gas to make it detectable. The complexity of an odor is a physical measure and it is opaque to consciousness. It is not possible to assess the complexity of an odor (i.e. to smell an 16 The situation is further complicated because the olfactory landscape is constantly moving itself and it is impossible (without a kinesthetic sense) to distinguish changes of our position in space from movement of smell objects in the olfactory landscape. In the odor world, movement is the norm, whereas in the visual or auditory world movement is a special case that can be detected against an unmoving background. There is no unmoving odor background. Phenomenology of Smells odor and estimate how many different types of molecules it is made of). It is therefore not meaningful to talk about the rose odor consisting of 300 smell objects. It consists of a single smell object. The smell of a rose that sits on a chocolate cake may be regarded as two smell objects ("rose" and "chocolate") because the two smells are so distinct and familiar that they will refuse to form a single smell object17. Often, to be able to claim that there are two objects, a temporal relation will help. A change in odor may well be interpreted as the addition of a second smell object although the two smells would constitute a single object if they would completely overlap temporally18. In any case, a given mixture of unknown odors will always be perceived as a single odor object. The olfactory world falls into coexistent objects through our experience in naming odors. This is what the wine tester uses to be able to smell several objects (tar, cherry, peach, etc.), where someone else may only smell a single object, wine. The individuation of objects presupposes acquaintance with them. This is in contrast to the a priori objectivity of visual perception, where order and permanence individuate objects. Ontology of Smells 5: Completeness of Object Determination In visual perception, an object is never given fully. There always is a backside and an interior and finer visual structure. As Husserl points out, this results in a situated consciousness which will only be able to experience something from its own 17 It is important to note that this has nothing to do with the rose and the chocolate cake being two actually distinct objects. A bar of rose-scented chocolate would present two smell objects. 18 If the rose smell and the chocolate smell appear at the same time and disappear at the same time they are more likely to be regarded as a single smell object than when the rose smell is added to an already existing chocolate smell. Phenomenology of Smells perspective. Does this perspectiveness persist in olfactory phenomenology? Odor objects are non-spatial, so there is no backside and no interior. There also is no finer structure of the object that could be probed in more detail because within a sniff, while the aspects of an object unfold, there is no way to "look closer" and the next smell will know the next object, that will also be completely known. The choice of "determining more closely, which is a fulfilling process, or (...) as a counterpart, disappointment, annulment of sense, and crossing out." (p. 22) in visual phenomenology is replaced by confirmation or crossing out in the olfactory phenomenology. The question is "Is there a smell?" and if this question is answered in the affirmative, the smell is known from all sides and from inside out. Every smell object is a completely determined object. Husserl talks about "the idea of the completely determined object, of the object that would be determined through and through, known through and through, where every one of its determinations would be purified of all indeterminacy" (p. 20). He calls this an "unattainable idea" (p.21) because the very structure of perception "excludes such a knowledge in which the tension would collapse between the object and the How of determination". In odor perception, the tension does not exist, the object and the How of determination are congruent19. The determination of a smell object is not at the level of perception, it exhausts itself in olfactory phenomenology in the attempt to name the odor. "Naming" the odor is placing the object into a (experienced or remembered) smell landscape. 19 Husserl's examples here are tactile and visual: "We always have the external object in the flesh (we see, grasp, seize it), and yet it is always at an infinite distance mentally." (p. 21) Phenomenology of Smells Ontology of Smells 6: Affection Affection is the ability of phenomenological content to attract or repulse the ego. Husserl uses an auditory example: "For example, a soft noise becoming louder and louder takes on a growing affectivity in this materially relevant transformation; the vivacity of it in consciousness increases. This means that it exercises a growing pull on the ego. The ego finally turns toward it. However, examining this more precisely, the modal transformation of affection has already occurred prior to the turning toward. Along with a certain strength that is at work under the given affective circumstances, the pull proceeding from the noise has so genuinely struck the ego that is has come into relief for the ego, even if only in the antechamber of the ego." (p. 166). This description could as well be the description of an odor increasing in intensity. It could also describe a light, a sweet taste, a touch, a bodily feeling of unbalance, and any other possible perception. In affection, a universal feature of phenomenology has been discovered. Preliminary Remarks and Future Plans This sketch of olfactory ontology points towards a phenomenology that does not limit itself by the special structure of perception in one modality. The ontology is clearly not meant to be complete. There is much more to say about the "phenomenology of the socalled unconscious" (p. 154)20. The discussion of temporality presented here does not 20 The "unconscious" and the "becoming conscious" are closely connected to affection. Husserl himself writes: "Accordingly, the problem of affection returns once more with respect to what is elementary, and in particular it returns as the problem of whether affection is not already an essential condition for the Phenomenology of Smells even attempt to establish a structure of olfactory time - the ontology of time that would emerge if all information would be in the olfactory format21. I also did not discuss the role of the body, which has a much more fundamental role in olfactory phenomenology than in visual phenomenology. The body has been given its important status in MerleauPonty's Phenomenology of Perception; however, Merleau-Ponty arrived at his conclusion while relying on visual phenomenology even more than Husserl. I also did not discuss in any depth the related and very important question of what role movement plays in olfactory consciousness22. Furthermore, olfactory memories and olfactory imagination are very different from visual memories and imagination and an analysis of memories and imagination would further clarify the underlying ontologies. emergence of every constitutive synthesis, and whether both of these must not go together: a preaffective characteristic of the elements, with the essential presuppositions for the formation of unity proper to the pre-affective character, and the affection itself." (p. 165). In smell perception the unity of affection and consciousness is striking. Often, if somebody asks 'Is there a smell around here?', with the next inhalation we can consciously smell an odor. The inhalation before transported the exact same stimulus to our olfactory epithelium, yet it did not result in a smell experience. In neuroscience this is called top-down influence, or attention. 21 This omission is despite the great interest in a phenomenology of time consciousness. Several recent works are concerned with this topic (The Specious Present: A Neurophenomenology of Time Consciousness, Francisco J. Varela and Wooden Iron? Husserlian Phenomenology Meets Cognitive Science by Tim van Gelder, both in Jean Petitot, Francisco J. Varela, Bernard Pachoud, and Jean-Michel Roy (editors) (1999) Naturalizing Phenomenology - Issues in Contemporary Phenomenology and Cognitive Science Stanford: Stanford University Press and How to, and how not to, bridge computational cognitive neuroscience and Husserlian phenomenology of time consciousness by Rick Grush in Synthese 153(3), 417-459, 2006 and references therein). The reason for this interest is in that time consciousness is a perfect topic for combining phenomenology with cognitive neuroscience. This allows also another level to the analysis presented here. If the neuroscience of time consciousness works according to the same fundamentals in all perception, it is fair to assume that there is something fundamental to the phenomenology. However, if the time consciousness of vision and smells is implemented in different ways, resulting in different experiences, it probably does not reveal anything fundamental about time and the world. 22 The role of movement in (visual) phenomenology is discussed in several contributions to Jean Petitot, Francisco J. Varela, Bernard Pachoud, and Jean-Michel Roy (editors) (1999) Naturalizing Phenomenology Issues in Contemporary Phenomenology and Cognitive Science Stanford: Stanford University Press Phenomenology of Smells I am sure there are more holes in this ontology. However, my aim here is to clarify the strategy for a much more ambitious project. I propose that through systematic reflection and analysis of all consciousness, regardless of modality, the fundamental structure of consciousness and its objects can be elucidated. From there, the adaptations of this system to different modalities, objects, and contexts need to be described. If this project is followed through, the importance of space and time for phenomenology will decrease, whereas affection, "the so-called unconscious", and embodiment will emerge as the concepts fundamental to all phenomenology. Phenomenology of Smells Bibliography Edmund Husserl (2001) Analyses Concerning Passive and Active Synthesis - Lectures on Transcendental Logic translated by Anthony J. Steinbock, Dordrecht (Netherlands): Kluwer Academic Publishers David Woodruff Smith (2007) Husserl New York: Routledge Maurice Merleau-Ponty (1962) Phenomenology of Perception translated by Colin Smith, New York: Routledge Jean Petitot, Francisco J. Varela, Bernard Pachoud, and Jean-Michel Roy (editors) (1999) Naturalizing Phenomenology - Issues in Contemporary Phenomenology and Cognitive Science Stanford: Stanford University Press Constance Claasen, David Howes, and Anthony Synnott (1994) Aroma - The Cultural History of Smell New York: Routledge Mark M. Smith Berkeley (2007) Sensing the Past - Seeing, Hearing, Smelling, Tasting, and Touching in History Berkeley: University of California Press