Benjamin D. Young is an Assistant Professor and Director of Graduate Studies in Philosophy, and graduate faculty in the Interdisciplinary Neuroscience Program and the Institute for Neuroscience at the University of Nevada, Reno. Ben conducts research at the intersection of Cognitive Neuroscience and Philosophy with a particular emphasis on olfaction. His research on consciousness, non-conceptual content, and the perceptible object of smell has been published in philosophical, psychological, and neuroscientific venues.
A post by Benjamin D. Young.
Imagine the smell of freshly baked cookies. Can you smell them right now? Unsurprisingly this is rather difficult but not impossible for some of us. Our ability to imagine smells is similar in many respects to our capacity for perceiving smells in general. It is affected by our attention to them and their importance within our daily lives. Over the years, I have used the unique features of olfaction to question general issues such as the anatomical realization of consciousness (Young, 2012), the difference between phenomenal consciousness and awareness (Young, 2014), as well as the representational format or formats of cognitive architectures (Young, 2015, 2019a). Smell is special and that carries over in cases where we lack direct sensory stimulation. Olfactory imagery, I have argued (Young, 2019b), is best conceived of as a form of mental imagery that inherits many of its properties from olfactory perception. What follows is a general overview of what we know about our imagined experiences of smells and how this suggests further directions of research exploring the boundaries of mental imagery.
Some used to claim that it is impossible to self-generate experiences of smell (olfactory qualities) (Engen 1982; Crowder and Schab 1995; Herz 2000). In Young 2019b, I show that claim to be unjustified, and yet, the vividness of the imagined olfactory quality is reported as rather week by comparison to visual imagery. Additionally, the proportion of the population who claim to experience olfactory imagery is almost the converse of visual imagery. Olfactory imagery is, by comparison to visual imagery, quite similar to the differences we observe between visual and olfactory perception.
The vividness of the imagined olfactory quality, the duration of the reported experience, and the frequency at which these state occur are all similar to olfactory perception. Our perception of smells is reported as weaker than visual experiences. We rather infrequently pay attention to and report the smells transiting our nostrils. What is rather interesting about the commonalities between olfactory perception, in general, and imagery, in particular, is that the same variables that increase olfactory perceptual acuity and explain expertise amongst professionals, can also be shown to mediate the capacity for olfactory imagery, the vividness of the experienced olfactory quality, the duration of these experiences, and their frequency.
In general, olfactory perceptual acuity (and expertise) is not mediated by an increased conceptual repertoire (Young, Keller, & Rosenthal, 2014; Majid, Speed, Croijmans, & Arshamian, 2017), rather there is a direct relation between one’s number of experiences and perceptual acuity. Relatedly, your capacity for olfactory imagery increases in relation to the regularity with which you entertain olfactory experiences. Not only is the amount of experience related to both perceptual acuity and imagery, but it has a direct impact upon our perceptual acuity and capacity for olfactory imagery as well. But here comes the tricky question – what exactly counts as an imagined smell in a person’s private phenomenology and how can we measure it?
Recent research has vindicated our capacity for retrieving memories of smells with olfactory qualities. We’ve also observed a capacity for imagined smell experiences that match their perceptual sensory qualities (for a fantastic, but slightly dated review, cf Arshamian and Larsson 2014). Yet, given the role of subjective measures in olfactory imagery, it is worthwhile to employ objective measures to corroborate that participants are experiencing smells, and that these are similar to (or the same as) veridical olfactory perceptual states.
In experimental settings, the subjective reports of participants are validated using objective behavioral, physiological, and cortical measures that are correlated with properties of perceived olfactory quality.
The behavioral and physiological characteristics of olfactory perception are preserved across occurrences of olfactory imagery, such that the individual’s respiratory rate, heart rate, sniffing behavior both in terms of rate and volume of sniffs all have the same properties during olfactory imagery as they do in perception of olfactory qualities. … [O]ur overall heart rate and respiratory rates … are preserved during olfactory imagery of unpleasant smells— physiological responses and behavioral measures mimic that of veridical perception. Furthermore, neuroimaging using PET scans and fMRI have shown that the areas of olfactory perceptual processing are activated during olfactory imagery and bear a striking resemblance to those that occur during veridical olfactory perception (Young, 2019b, p. 5).
These objective measures support the claim that we can self-generate an experience of olfactory quality when experiencing an imagined smell. Research has also shown that the same motorsensory contingencies that support olfactory perception can affect our capacity to imagine smells. Maintaining the same sniffing patterns as if one was smelling has been shown to enhance the vividness of the imagined smell, while occluding the nostrils decreases our ability. Additionally, those suffering from Anosmia (the inability to perceive smells) show a deficit in olfactory imagery that is directly related to the duration and degree of their deficit in olfactory perception. However, the prevalence of imagined smells vastly expands if we do not limit our conception of them to only self-generated, voluntary experiences of (orthonasal – from the front of the nose) olfactory qualities.
Involuntary imagined experience of smells have been documented in cases of olfactory dreams, hypnotic suggestion, and most prevalently in the form of phantosomia. Phantosomia, whereby subjects report the occurrence of a phantom smell, occur throughout the population in proportion to olfactory imagery. The sensory nature of reported episodes of phantosomia show an interesting conservation of the valence of olfactory mental imagery that is apparent in olfactory memories. The vast majority of individuals who report having olfactory hallucinations report the olfactory quality of the experience as having a negative valence (i.e. smoky, burnt, or fecal), which is similarly seen in reports from adults of their olfactory memories. Remembered experiences of smells are predominantly of olfactory qualities with a negative valence, such that experimental research indicates olfactory memory more frequently encodes and stores negative smells (Larsson, Oberg-Blavarg, & Jonsson, 2009). However, a rather odd asymmetry appears within olfactory memories when comparing general with autobiographical memories. While olfactory memories and hallucinations are usually unpleasant, lack detail, and seem weak, autobiographical memories are reported as being highly vivid in terms of the re-experienced olfactory quality, its fine-grained detail, and most interestingly its positive valence (for an excellent in depth review cf. Hackländer, Janssen, & Bermeitinger, 2018). Yet, this discrepancy seems less puzzling if we note olfaction’s general formative difference with vision and our semantic conceptual abilities (Young, 2019a). Olfaction it has been argued implements a format of representation that is at odds with that employed by vision and our conceptual (semantic) cortical processing centers.
As I speculate (Young, 2019b), the reason for the difference between general olfactory memories and the pleasant vivid nature of autobiographical memories might be the period when the latter are encoded. There is an ‘olfactory memory bump,’ found when experimentally probing for autobiographic memories, which locates the developmental period of these memories as clustering around the ages of 6-11. During this period of development, olfactory acuity is just beginning to peak, yet it is before the acquisition of linguistic tags for smells begins to mediate olfactory perception. Thus, autobiographic olfactory memories from this early period are encoded and stored in a representational format that is incompatible with the format employed by our conceptual (semantic) processes and generally at odds with our visuocentric dominate cortical processing. Thus, these experiences are somewhat immune to interference effects within long-term memory storage and upon retrieval are less dominated by visual imagery.
If the discrepancy of smells format might be used to explain this phenomena, does it appear in other areas of imagination? For instance, retronasal (from the back of the throat) olfactory imagery of flavors is an under-explored topic, but assuming a conservation of format between the two senses of smell (Smith, 2015), might we anticipate failures of imagined sensory qualities when considering the integration of cross-modal qualities? Not only might we anticipate incongruency, but olfaction might even be deployed as a means of testing directional effects requiring integration across modalities. We know such directional effects occur in cross-modal perception. For example, a visual cue can enhance odor identification (when the stimuli are semantically related) and a congruent odor can cause a decline in performance in visual (color) working memory tasks (Tamura, Hamakawa, Okamoto, 2018). From these findings it seems quite likely that if mental imagery is a form of perceptual processing, then similar effects should be predicted in directional modulation of our capacity for cross-modal (visual and olfactory) imagery. In conclusion, the future directions of research on mental imagery employing olfaction could provide boundless areas to fruitfully test the limits of our imagination.
And for those less empirically inclined, who prefer more traditional methods of pumping metaphysical intuitions, consider this: if I am correct about mental imagery being a form of perceptual processing, what could anosmic Mary know about smells while inside her odorless laboratory?
Reference:
Arshamian, A., & Larsson, M. (2014). Same same but different. Frontiers in Psychology, 3, 1–8. https:// doi.org/10.3389/fpsyg.2014.00034.
Crowder, R. G., & Schab, F. R. (1995). Imagery for odors. In R. G. Crowder & F. R. Schab (Eds.), Memory for odors (pp. 93–107). Mahwah, NJ: Erlbaum.
Engen, T. (1982). The perception of odors. Toronto: Academic Press.
Hackländer, R. P. M., Janssen, S. M. J., & Bermeitinger, C. (2018). An in-depth review of the methods, findings, and theories associated with odor-evoked autobiographical memory. Psychonomic Bulletin& Review. https://doi.org/10.3758/s13423-018-1545-3.
Herz, R. S. (2000). Verbal coding in olfactory versus nonolfactory cognition. Memory and Cognition, 28, 957–964. https://doi.org/10.3758/BF03209343.
Larsson, M., Oberg-Blavarg, C., & Jonsson, F. U. (2009). Bad odors stick better than good ones. Experimental Psychology, 56(6), 375–380. https://doi.org/10.1027/1618-3169.56.6.375.
Majid, A., Speed, L., Croijmans, I., & Arshamian, A. (2017). What makes a better smeller? Perception, 46, 406–430. https://doi.org/10.1177/0301006616688224.
Smith, B.C. (2015) ‘The Chemical Senses.’ In Mohan Matthen (ed.), The Oxford Handbook to Philosophy of Perception. New York, NY, USA: pp. 314-353
Tamura K, Hamakawa M, Okamoto T (2018) Olfactory modulation of colour working memory: How does citrus-like smell influence the memory of orange colour? PLoS ONE 13(9): e0203876. https://doi.org/10.1371/journal.pone.0203876
Young, B. D. (2012). Stinking consciousness! Journal of Consciousness Studies, 19, 223–243.
Young, B. D. (2014). Smelling phenomenal. Frontiers in Psychology, 5, 713. https://doi.org/10.3389/fpsyg.2014.0071.
Young, B. D. (2015). Formative non-conceptual content. Journal of Consciousness Studies, 22, 201–214.
Young, B. D. (2019a). Smell’s puzzling discrepancy. Mind and Language. https://doi.org/10.1111/mila.12233
Young, B.D. (2019b) Olfactory imagery: is exactly what it smells like. Philosophical Studies. https://doi.org/10.1007/s11098-019-01371-4
Young, B. D., Keller, A., & Rosenthal, D. (2014). Quality-space theory in olfaction. Frontiers in Psychology, 5, 1. https://doi.org/10.3389/fpsyg.2014.00001.