J . Smith Decoding the psychological dimensions of human odor perception has long been a central issue of olfactory research. It is debatable whether verbal attributes can appropriately reflect the quality features applied by nonprofessionals. PM Many investigators have focused on confirming the existence of a hedonic factor that has been based on theoretical considerations or proposed by previous studies. Yousem AN Rinck C Land . Based on a subjective summary of these verbal reports, Henning proposed 6 odor qualities and arranged them as corners of a prism. . RM Finding the most appropriate number between these 2 extremes has been a challenge, especially when prior knowledge of the grouping and external validation criteria has been missing (Everitt 1979). Herz and von Clef (2001) investigated the influence of verbal labels on odor descriptions by presenting identical odors with different labels in 2 several test sessions (violet leaf as “fresh cucumber” or “mildew”). The dimension could, however, be labeled with terms that refer to the semantic arrangement of the attributes like garden, vegetable, fresh, organic, or ecological. D DH DB The 4 classification studies that performed cluster analysis (Døving 1970; Chastrette et al. In a simulation study, they demonstrated a good fit of averaged data to standard MDS models, whereas these models failed to represent the data of any individual subject appropriately. KR Not surprisingly, several studies reported a poor agreement among subjects in pairwise ratings of odors (Yoshida 1964; Gregson 1972; Berglund et al. Lundström In a cluster analysis, the final number of groups can possibly be between 1 and n, where n is the number of objects assessed. 1999; Distel and Hudson 2001; Hudson and Distel 2002). Ashby Features of the sensory stimulus: The chemical structure of an odorous compound strongly determines its perceived quality. Ueno (1993) asked 20 Japanese and 20 Nepalese (Sherpa) participants to sort 20 Japanese food flavors based on their perceived similarity. However, a large number of compounds is not necessarily more representative than a well-selected smaller stimuli set. 1978) or presented compounds as diverse as possible from a perceptual or a chemical perspective (Berglund et al. . Haddad Overview of psychological classification studies. 1968), most of them have, in fact, pursued different aims without stating them explicitly. Published by Oxford University Press. Carrie However, the degree to which they reflect “natural” odor categories or are completely arbitrary remains questionable. SOR may actually benefit from the availability of perceptual odor spaces, while they are little promising in the development of basic classifications. Its impact on language is especially strong not least because of the sparse olfactory terminology of untrained subjects. Hence, a valid olfactory classification requires the reliability of both perception and verbal expression. K S From the different categories, only source labels refer to real, distinct percepts and hence seem to provide most applicable rating standards—especially for untrained panelists. Intercultural research has shown that culturally acquired experience mainly affects the evaluation of familiar versus unfamiliar odors rather than perceptual processes in general. Hence, odors should have been selected to represent the full extent of olfactory space. . A Lawless 1988; Wysocki et al. RA Zellner RG An index of similarity is derived across all panelists from counting the joint occurrence of any possible pair of odors in the same group. To facilitate a satisfactory communication despite this inaccuracy of everyday language, perfumers and fragrance companies have established a professional terminology. They found significant differences for ratings of the fixed compounds between both conditions with odors being rated as more similar in the presence of a very disparate smell (vinegar). M For full access to this pdf, sign in to an existing account, or purchase an annual subscription. Aronov HS CJ Features of the sensory percept:Henning (1916) was the first who directly classified olfactory percepts by arranging verbal odor descriptions. JW C IE Maute I Courcoux Gottfried Harper and colleagues (1968) characterized the language people use to capture odors as “a borrowed one” (p. 84), “a language of substances and things” (p. 167). 2007; Djordjevic et al. R Although Henning’s model has been repeatedly tested and falsified (Dimmick 1922; MacDonald 1922; Findley 1924; Hazzard 1930), many studies have followed his approach and applied verbal reports of odor perception to established odor classifications. Siddiqi Psychiatry Res. In a number of the classification studies we reviewed, intensity effects were controlled. Many systems have been proposed-by … It contains as much as 3102 odor samples that have been characterized with about 270 different attributes. Glusman These will reflect natural perceptual dimensions more appropriately than predefined verbal descriptors but they may change for every new pair of odors and they may remain largely unknown—to the participants as well as to the researcher. Several authors noted that odor classifications have been particularly affected by the linguistic or semantic arrangements of (supposed) odor sources rather than the sensory characteristics of odors (Chastrette et al. When Lawless (1989) first applied a sorting task to generate MDS data, he raised the question whether different data collection approaches yield comparable olfactory spaces. S One patch is located in each of the two main compartments of the back of the nose. R . 2001; Zozulya et al. There has been a constant matter of scientific debate whether mental categories are innate and thus universal or learned and therefore experience dependent. If we could establish the odor classification technology, we would expect various new technology since human being requires five sences to acheive higher quality information processing and sophistcated decision making. WW Gottfried Martinetz S 1993; Pierce et al. CB Analysis of individual differences in multidimensional scaling via an n-way generalization of “Eckart-Young” decomposition, Classification of odors and structure-odor relationships, Analysis of a system of description of odors by means of four different multivariate statistical methods, A multidimensional statistical study of similarities between 74 notes used in perfumery, Determining the number of clusters in cluster analysis, Graded structure in odour categories: a cross-cultural case study, Culture and odor categorization: agreement between cultures depends upon the odors, Semantic, typicality and odor representation: a cross-cultural study, Odour-evoked autobiographical memories: psychological investigations of proustian phenomena, Commission internationale de l’Éclairage proceedings, 1921, The importance of language in describing perceptions, A review and evaluation of exploratory factor analysis practices in organizational research, Workplace, age, and sex as mediators of olfactory function: data from the National Geographic Smell Survey, Best practices in exploratory factor analysis: four recommendations for getting the most from your analysis, Multidimensional scaling of perceived odour of bicyclo [2.2.1] heptane, 1,7,7-trimethylbicyclo [2.2.1] heptane and cyclohexane derivatives, Identification of olfactory dimensions by semantic differential technique, The use of semantic differential scaling to define the multi-dimensional representation of odors, Olfactory perceptual space models compared by quantitative methods, The smell map: commonality of odour perception confirmed, How to map the affective semantic space of scents, The human capacity to transmit olfactory information, Odor quality: discrimination versus free and cued identification, Perception of everyday odors: correlation between intensity, familiarity and strength of hedonic judgement, Judgement of odor intensity is influenced by subjects’ knowledge of the odor source. KORYO (Flavor & Fragrances), No.100, 45-53. Abdi DG Braun Wise et al. PJ C Wysocki An example is the widely applied color metric established by the International Commission on Illumination (CIE) in 1931 (CIE 1932) and 1964 (CIE 1964), respectively. A Seven PJ White CJ Grandjean Olsson Various notions concerning the relationship between properties of molecules and their corresponding odors have appeared, but none has attained acceptance as a legitimate theory (Cain, 1988; Rossiter, 1996, Chastrette, 1997). 1973; Moskowitz and Gerbers 1974; Yoshida 1975; Schiffman et al. Kringelbach Chrea T This, in turn, might influence intensity as well as quality features (Figure 1). F 1988; Lawless 1989; Prost et al. Davis Lapid eCollection 2013. Kobayakawa Several classifications of odors have been proposed, but none have been generally accepted. Amoore Gutiérrez ED, Dhurandhar A, Keller A, Meyer P, Cecchi GA. Nat Commun. In this paper, the detection and classification of human body odor by E-nose measurement have been demonstrated. Each manifest variable is expressed as linear combination of common factors that explain the shared variance plus factors of unique variance and measurement error. In summary, olfactory ratings appear to be stable over short periods of time. MacCallum C Camus To address this issue, recent studies have revived early approaches (Amoore et al. Corwin Rouby P WS 1973; Coxon et al. Thus, classification studies have usually applied analysis approaches that either search for a parsimonious but meaningful dimensionality of the data set, like exploratory factor analysis (EFA), principal component analysis (PCA), and multidimensional scaling (MDS), or summarize odors to more homogenous groups, like cluster analysis. Participants were asked to sort 40 odorants based on their perceptual similarity in as many groups as they felt necessary. In almost all M/Ts, odor-evoked responses can be classified as excitatory, inhibitory and unresponsive, based on the initial change in firing rate after odor presentation. Philos Trans R Soc Lond B Biol Sci. 1996; Lavin and Lawless 1998; Morrot et al. (1978) questioned “if an adequately universal but relatively small and manageable set of reference odorants can be developed” (p. 192). Applebaum . Davis (1979) and Gregson (1972) showed that panelists actually differ in the comparison strategies they apply. R Foods. Hummel CJ Based on the research reviewed, we give preference to MDS and EFA for the analysis of nonverbal data sets and profile data, respectively. Flinker This is not intended as an endorsement. 1977). Uchida This is, however, not easily attained by EFA: For a given odor, several factor scores (positions in the odor space) can be calculated that perfectly fit the factor model but vary considerably. HS 2004). (1999) applied the same approach and extended the German–Japanese sample by 39 Mexican subjects. (2000) collected dissimilarity ratings for a set of 4 fixed odorants (licorice, mint, mothballs, rose) and either vinegar or rubbing alcohol. JD . To uncover the criteria applied by subjects, researchers might ask them to provide verbal labels for their nonverbal arrangements (Stevens and O’Connell 1996; Chrea et al. An examination of relationships between the pleasantness, intensity, and concentration of 10 odorous stimuli, Influence of age and age-related diseases on olfactory function, Sex differences in odor identification ability: a cross-cultural analysis, An electrophysiological study of odour similarities of homologous substances, Evaluation of human body odors: methods and interpretations, Odor quality: semantically generated multidimensional profiles are stable, Comparison of odors directly and through profiling, Categories as acts of meaning: the case of categories in olfaction and audition, Names and categories for odors: the veridical label, Fragrances of the World 2012: Parfums du Monde, Multivariate analysis in sensory evaluation, Evaluating the use of exploratory factor analysis in psychological research, Affective dimensions of odor perception: a comparison between Swiss, British, and Singaporean populations, Further studies of Henning’s system of olfactory qualities, The application of exploratory factor analysis in applied psychology: a critical review and analysis, Stimulus selection in the design and interpretation of olfactory studies, Cross-modal correspondence between vision and olfaction: the color of smells, Sulfur-containing odorants in fragrance chemistry, Common factor analysis versus component analysis: some well and little known facts, Dissociable codes of odor quality and odorant structure in human piriform cortex, Odour similarities and their multidimensional metric representation, Odor quality similarity scaling and odor-word profile matching, Concentration-dependent changes of perceived odor quality, The colorimetric properties of the spectrum, Categorical perception: the groundwork of cognition, Odour description and odour classification: a multidisciplinary examination. 2006; Bensafi et al. Prost Along with this terminology, odor professionals have acquired cognitive categories that allow them to perceive a continuous space of odors in discrete conceptual categories. Takahashi Several studies addressed this issue and found differences in MDS solutions caused by different scale levels of the data (Rao and Kaltz 1971; Humphreys 1982; Bijmolt and Wedel 1999). Although several studies have addressed the impact of particular variables on odor arrangements (Yoshida 1975; Schiffman and Dackis 1976; Davis 1979; Jeltema and Southwick 1986; Chastrette et al. Chrea et al. odor classification of various sources for fire such as household burning materials in [21]. R The smell map: is there a commonality of odour perception? Tait Rubin . 2006; Howard et al. Predicting natural language descriptions of mono-molecular odorants. Nilsson Gross-Isserhoff 1977; Carrasco and Ridout 1993). Although numerous investigators have tried to establish classification systems to facilitate “differentiation, recognition, and identification” (Harper et al. Remarkably, odor quality is not only a matter of the stimuli offered but also of how these are presented and to whom. 2009). . C USA.gov. S WF Remarkably, Wright (1929) and Stiles and Burch (1959) reported considerable differences in the color-matching functions of the observers they had tested. This prevalence of PCA over EFA does not just apply to classification studies but has also been found in other areas of psychological research (Ford et al. Odor and smell classification and measurement. Chem Senses. Empirical evidence for this notion is provided by a study of Boelens and Haring (1981). A Lancet G Among other rating tasks, subjects were asked to report a memory evoked by each smell, to describe its function, and to generate a name for what they supposed the odors could be. I Issanchou However, both approaches are based on distinct mathematical assumptions even though often yield fairly similar results. It represents objects as points of a (preferably) low-dimensional space in a way that interpoint distances best match the measured (dis)similarities of associated objects. Other studies used empirical cross-adaptation approaches to investigate the relation between odor classes and receptor types (Cain 1970; Todrank et al. . Wysocki This has also been true for olfactory classifications: The selection of odors has determined the structure and meaning of odor arrangements. Hence, when subjects have been instructed to compare an odor with an attribute as “birch bark” (Dravnieks 1985), they might have pictured odor sources or appropriate situations (walk in the woods, collect mushrooms) rather than a distinct smell. However, other studies demonstrated high interrater agreement for verbal ratings (Dravnieks 1982; Jeltema and Southwick 1986) and considerable interindividual variety for nonverbal techniques (Yoshida 1964; Gregson 1972; Berglund et al. Various odors have been mixed naturally in our living environment. . JM D AN M Aarts Rawcliffe MJ JM Sasaki The act or process of smelling. However, classification studies have usually not explained why they applied either method. These findings suggest that pleasantness is a generic factor of olfactory perception, which is subdivided in more specific facets related to the functions and effects of odors on humans. 1990; Madany Mamlouk et al. Hence, the unique and complex interaction between language and olfaction should be assessed more thoroughly. However, as the organization of this space is under investigation, the matter of representativeness is vague and classification studies have dealt differently with this issue: Several studies of the works we reviewed did not report selection criteria at all (Wright and Michels 1964; Woskow 1968; Jeltema and Southwick 1986; Stevens and O’Connell 1996; Dalton et al. Saito 2002). . Gilbert . Elderly subjects might be excluded from classification studies to reduce the impact of physiological impairments. Although Chastrette (2002) assumed a high-dimensional olfactory space, most of the reviewed studies reported between 2 and 4 perceptual dimensions. Not surprisingly, intra- and interindividual variances have also been observed for basic perceptual ratings in other sensory modalities, as in color vision (Viénot 1980; North and Fairchild 1993; Alfvin and Fairchild 1997). BJ 2018 Oct 24;7(11):176. doi: 10.3390/foods7110176. Lawless (1991) and Lawless et al. 2011; Delplanque et al. 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