Kulturphilosophie of Smell in the Novel “Against Nature” (“À rebours”) by J.-C. Huysmans

The olfactory space in the novel “Against the Grain” (“À rebours”) by J.-C. Huysmans is for the first time analysed from the perspective of Kulturphilosophie. A number of methods, particularly analytical and historical-cultural, can be used to examine this topic. At the same time, the approach of Kulturphilosophie can be applied to the semantic field of the phenomenon of smell. The article deals with the research experience of flower-images and perfume aspects concerning odoric passages in the novel. The text of the novel “Against the Grain” is examined in detail. Specific features of the use of natural, artificial, metaphysical odorisms or components referring to them are revealed. Particular attention is paid to the meaning and symbolism of some of the scents included in the novel, which have come to mark the epoch of “fin de siècle”. On the basis of the analysis of the novel’s olfactory, the olfactory and near-olfactory passages composing the text’s odoristic universe are classified into four groups, taking into account the origin (natural – artificial), the type of perception (syncretic), reality or unreality of embodiment (real – metaphysical). The Kulturphilosophie approach to the novel “Against the Grain” makes it possible to reveal the objectifications of smells, to structure them, to trace their role in revealing the author's creative intentions, and to decipher their hidden meanings, comparing them with cultural trends and creative experiments of the “fin de siècle” epoch.

Drawing the Borders of Olfactory Space

In studies of vision and audition, stimuli can be chosen to span the visible or audible spectrum; in olfaction, the axes and boundaries defining the analogous odorous space are unknown. Features governing the physical transport of molecules to olfactory receptors are sufficient to reliably classify novel molecules as odorous or odorless (AUROC = 0.97). Applying this model to a database of all possible small organic molecules, we estimate that over 30 billion possible compounds are odorous, 6 orders of magnitude larger than current estimates of 10,000. Remarkably, nearly all transport-capable molecules are odorous, suggesting broad collective tuning of olfactory receptors. Defining the boundaries of odor perception will enable design of experiments that representatively sample olfactory space and efficient search for novel odor compounds.

Navigation Towards the Source Through Chemosensory Strategies and Mechanisms

Asymmetry of bilateral visual and auditory sensors has functional advantages for depth visual perception and localization of auditory signals, respectively. In order to detect the spatial distribution of an odor, bilateral olfactory organs may compare side differences of odor intensity and timing by using a simultaneous sampling mechanism; alternatively, they may use a sequential sampling mechanism to compare spatial and temporal input detected by one or several chemosensors. Extensive research on strategies and mechanisms necessary for odor source localization has been focused mainly on invertebrates. Several recent studies in mammals such as moles, rodents, and humans suggest that there is an evolutionary advantage in using stereo olfaction for successful navigation towards an odor source. Smelling in stereo or a three-dimensional olfactory space may significantly reduce the time to locate an odor source; this quality provides instantaneous information for both foraging and predator avoidance. However, since mammals are capable of finding odor sources and tracking odor trails with one sensor side blocked, they may use an intriguing temporal mechanism to compare odor concentration from sniff to sniff. A particular focus of this article is attributed to differences between insects and mammals regarding the use of unilateral versus bilateral chemosensors for odor source localization.

On the dimensionality of olfactory space

We recently presented an estimate of the number of mutually discriminable olfactory stimuli at one trillion (1). Subjects were asked to sniff mixtures of molecules with increasing component overlap selected from a panel of 128 isointense structurally and perceptually diverse monomolecular odorants (2). We considered stimulus pairs discriminable when the majority of subjects could significantly discriminate them at p=0.05, a conventional statistical threshold given our sample size. From these empirical data, we estimated that human discriminative capacity exceeds one trillion olfactory stimuli. Several readers have pointed out that such extrapolations are sensitive to underlying assumptions about the chosen significance threshold (3) and the dimensionality of olfaction (4). It is important to note that any exponential function will be sensitive in this way, and the goal of our model was not to identify the exact number of discriminable olfactory stimuli, or even the exact mathematical bounds, but an estimate of the order of magnitude of human discriminatory power across a population of human subjects. This was not clearly stated in our paper, and we agree that contradictory references to a “lower limit” and an “upper bound” were confusing. The central argument in (4) is that our estimation method assumes that the dimensionality of olfactory space is large. We agree that the high-dimensional nature of olfaction is indeed an assumption, and we should have stated this explicitly in our paper (1). Even if we follow this logic of the models presented in (4), purely geometrical calculations show that our results hold if the dimensionality of olfactory representations is D≥25. The dimensionality of olfaction is a question of interest to everyone, and while we do not know for sure, all available evidence suggests that olfaction is a high-dimensional sense. The olfactory system is wired to keep information from the ~400 odorant receptors strictly separated, so it is plausible that olfaction operates at least in 400-dimensional space. This is an important topic of discussion in olfaction, and we welcome continued debate of the dimensionality of smell and how this impacts human olfactory perception.