CH YK Kikuchi . 2001; Sakai 2005) or verbal label attached to an odor. D Lundström Williams 2004; Cheong and Lee 2008), but none of them have prevailed to adequately solve the problem. Kathrin Kaeppler, Friedrich Mueller, Odor Classification: A Review of Factors Influencing Perception-Based Odor Arrangements, Chemical Senses, Volume 38, Issue 3, March 2013, Pages 189–209, These reference odors are usually meant to represent specific perceptual qualities; that is, they act as olfactory counterpart to verbal descriptors. . LR Walther Hatayama Based on the research reviewed, we give preference to MDS and EFA for the analysis of nonverbal data sets and profile data, respectively. Rolls Lawless (1989) applied a time-efficient alternative to pairwise similarity ratings: He adopted a method used in personality research (Rosenberg and Park Kim 1975) and asked subjects to sort odorants based on their similarity in as many groups as they considered necessary. Hence, a valid olfactory classification requires the reliability of both perception and verbal expression. To stabilize ratings, several of the reviewed classification studies have counterbalanced their stimuli sets (Wright and Michels 1964; Woskow 1968; Berglund et al. Olofsson Zellner Odor researchers should thus not lose sight of perception-based classification and focus on new approaches for establishing them. 2009; Ferdenzi et al. This lack of control might have produced variance in the data that has been falsely ascribed to odor quality (Berglund et al. However, a large number of compounds is not necessarily more representative than a well-selected smaller stimuli set. . Boyle T Bartoli Jap. AN Morrot If this information becomes available from contextual cues or memory, it will dictate perceptual ratings (Lorig and Roberts 1990; Distel and Hudson 2001; Herz and von Clef 2001; Herz 2003; Rolls et al. Out of 175 different descriptors, the vast majority pointed to odor sources (84.3%), 8.4% represented sense-specific qualities (fragrant, aromatic, rancid), and 6.7% described nonolfactory percepts (dry, heavy, sweet); 1 descriptor referred to pleasantness, 1 to an odor effect (full list is available from first author). Odor scientists as well as fragrance professionals have tried to establish comprehensive standards for the description, measurement, and prediction of odor quality characteristics. In a cluster analysis, the final number of groups can possibly be between 1 and n, where n is the number of objects assessed. . A LB 2004; Keller et al. Hence, the unique and complex interaction between language and olfaction should be assessed more thoroughly. Several classifications of odors have been proposed, but none have been generally accepted. 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. Herz (2005) proposed that this evolutionary meaning has caused the weak connection of odors and language. Maute Lombion S, Bechetoille B, Nezelof S, Millot JL. Distel In a number of the classification studies we reviewed, intensity effects were controlled. Sander . 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. 2008a, 2008b). But it may be questioned whether this number is sufficient to represent a presumably high-dimensional olfactory space. A great number of color systems has been developed to accomplish distinct tasks at different levels of detail (for an overview, see Kuehni and Schwarz 2008). 1998). Categorical dimensions of human odor descriptor space revealed by non-negative matrix factorization. S He presented 415 odorants to 6 participants and asked them to freely verbalize their perceptions. de Laumer To our knowledge, no study has yet compared the applicability of PCA and EFA to classification data. M 2009). SE Sulmont A third database that has been applied in several classification studies is published and regularly updated by Sigma-Aldrich. . Cain 2006 Oct;31(8):713-24. doi: 10.1093/chemse/bjl013. Maldjian Get the latest public health information from CDC:, Get the latest research information from NIH:, Find NCBI SARS-CoV-2 literature, sequence, and clinical content: Wise et al. Komukai Haddad A CP is a fundamental process in perception: It was first observed for color vision and has since been found in various perceptual domains (Harnad 1987).  |  . Bensafi Rouby Coxon JD Please enable it to take advantage of the complete set of features! P Smith . M SS The data analysis revealed that different from the Japanese sample, Sherpa did not apply a distinct category for “fishy” odorants. Belzung The latest version of the catalog (Sigma-Aldrich Company 2011) comprises profiles of more than 1600 aroma raw materials that have been characterized with 82 attributes. In this paper, the detection and classification of human body odor by E-nose measurement have been demonstrated. Hulshoff Pol S Tibshirani Preti n 1. the sense of smell 2. the act or function of smelling n. 1. the act of smelling. Takahashi Lawless HS We have proposed a scheme to minimize the humidity effect that is usually a serious problem for the detection of human body odor. D However, the same could not be found in either of the other two odor mixtures. Fabrigar P 2004), these effects have not been reported systematically so far. . Chem Senses. In summary, olfactory ratings appear to be stable over short periods of time. S Cotman Odor receptors on the antennae of a Luna moth. 2005). I T Odor researchers should nevertheless consider that the exclusion or underrepresentation of specific odor classes, especially of unpleasant odors, will yield biased classification systems. UG Dravnieks 1986). Cummings Ayabe-Kanamura et al. However, in many of the reviewed studies, we have found an overrepresentation of specific quality classes that has undoubtedly yielded in fragmentary and biased odor arrangements. It rather changes with other odor characteristics, contextual information, and personal experiences. 2000; Larsson et al. The pairwise similarity is evaluated in each possible dyadic combination of a set of odors on numerical or visual rating scales (Woskow 1968; Berglund et al. However, one should not simply assume 1) that olfactory perceptions are generally stable over time, 2) that different people perceive identical odorants in the same way, and 3) that different people verbalize their olfactory percepts consistently. . Participants were asked to sort 40 odorants based on their perceptual similarity in as many groups as they felt necessary. T CBR involves four step which are retrieve, reuse, revise and retain. However, the assumption of a single comprehensive color system that is rooted in a natural arrangement of stimuli is a fallacy. A rose by any other name: would it smell as sweet? JD 2004; Higuchi et al. PCs are linear combinations of the original variables and explain the entire variance of the data in successively decreasing proportions. D 2004, 2005), whereas those by odor professionals have usually not applied pleasantness as comparison criterion (Ennis et al. However, these criteria usually remain unknown. . Zhang X, Zhang K, Lin D, Zhu Y, Chen C, He L, Guo X, Chen K, Wang R, Liu Z, Wu X, Long E, Huang K, He Z, Liu X, Lin H. Gigascience. JM With the Atlas of Odor Character Profiles, Dravnieks (1985) published an extensive database from expert ratings: He carefully developed a 146-attribute list (Dravnieks 1975; Dravnieks et al. 2007; Dalton et al. Dawes CJ N Wright (1929) discarded the results of 10 participants due to “inaccuracy and unreliability” (p. 152). Paddick 2020. Various findings indicate that superior experience yields in odor arrangements that are distinct from the perceptional systems of nonprofessionals: 1) When data has been gathered from either experts or laymen, odor arrangements have varied with respect to the prevalence of a pleasantness factor. Schiet Participants were asked to smell 18 everyday odorants (6 familiar to Japanese, 6 familiar to Germans, 6 familiar to both groups) and to judge them against several perceptual characteristics. However, theoretical assumptions (Harper et al. 1973; Yoshida 1975; Boelens and Haring 1981; Ennis et al. 1973). Epub 2020 Apr 20. Nguyen MJ In addition to physiological effects, experience accounts for interpersonal differences in odor perception or evaluation, respectively. Classification studies have usually calculated MDS spaces from averaged group data (Woskow 1968; Døving 1970; Schiffman 1974a, 1974b; Coxon et al. With this sample size, researchers have usually found a trade-off between methodological requirements and practicability aspects. Tibbetts 1977), whereas most “semantic differential ratings tended to be widely distributed over subjects across scales” (Schiffman et al. Aggarwal Elmouaffek Hayes Howgate S COVID-19 is an emerging, rapidly evolving situation. This approach has been based on the assumption that intensity represents a distinct perceptual dimension—comparable, for instance, with color perception. Gutiérrez ED, Dhurandhar A, Keller A, Meyer P, Cecchi GA. Nat Commun. (2012) reported that within-individual variability does not increase with longer time intervals. However, the potential purposes of odor systems are diverse: They range from the allocation of odors in classes with appropriate labels over the identification of (hierarchical) relations between these classes and the features by which they may be distinguished to the establishing of an appropriate terminology, the depiction of blending rules, perceptual similarities, and finally the relations to physical, chemical, or functional criteria. PM Clin Toxicol (Phila). Jinks 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. 2013 Feb;51(2):70-6. doi: 10.3109/15563650.2013.767908. 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C Evaluating and classifying the odor pollution is important basis for analyzing the odor pollution. . 2) When attribute lists have been provided by experts and applied by laymen, terms have been understood and used differently by the untrained subjects (Lawless 1984; Solomon 1990, 1997). V In order to represent the different odor qualities appropriately, a minimum number of odors is required. . Tanifuji Even most basic aspects like an odor carrier and dilution (air, liquid) or the duration of its presentation may affect the perceptual evaluation. 1990) but without reporting their decision criteria appropriately or at all. KORYO (Flavor & Fragrances), No.100, 45-53. B MI 2004). F H . M B At the same time, it may have affected odor arrangements when the linguistic or perceptual categories of laymen have been captured and possibly blurred by professional terms. Among various contextual biases in sensory judgments, contrast effects are probably the most common (Lawless and Heymann 2010). 1973). Given that the presentation of familiar odors to nonprofessionals is meant to facilitate the already demanding task of odor evaluation, this is comprehensible. Hommet 1996; Lavin and Lawless 1998; Morrot et al. (2003) assessed 5 odorants at 7 different concentrations. (1991) confirmed the impact of perceptual context on quality judgments. The variance between 2 measures is largely attributable to sniff-to-sniff changes, that is, processes in the range of seconds or minutes. 1988; Dubois 2000; Rouby and Bensafi 2002). S doi: 10.1371/journal.pone.0073289. Odor classification: a review of factors influencing perception-based odor arrangements. H On the other hand, several authors have discussed that PCA tends to inflate loadings of variables and estimates of explained variance when compared with EFA (Widaman 1993; Fabrigar et al. . I Many systems have been proposed-by … PCA searches for m (m < p) dimensions that provide an alternative description of the data points minus the redundancy expressed by intercorrelations between the original variables. W D 1973; Coxon et al. Jr 1986; Fabrigar et al. Discriminability may also vary within a category given that some odors are perceived as more typical than others (Chrea et al. Dailey . C A T Subjects are asked to express their olfactory sensations verbally, but instead of actively generating verbal descriptions, they evaluate odors against fixed references. Even if a sufficiently representative yet relatively small set of odors can be found, the sensations of these odors are anything but accurate reflections of actual stimuli. However, this approach requires both the soundness of applied descriptors as well as the comparability of verbal and nonverbal procedures with respect to their results. However, if this notion is appropriate remains questionable (Chastrette 2002). 2006) or calculated from odor profiles (Madany Mamlouk et al. HT For future research, scientists should not only control for intensity effects by presenting compounds at equally intense dilutions. EV Gilbert S N Hummel . One patch is located in each of the two main compartments of the back of the nose. Howard B Kobayakawa 2001; Chrea et al. 1990; Prost et al. K 1973). Hence, odor arrangements have possibly factored out differences between subjects with the application of classical MDS models. Ly Mai But to this day none of them has sustained scientific scrutiny. Affective responses to odors do not mirror basic human emotions but rather reflect the “role of olfaction in well-being, social interaction, danger prevention, arousal or relaxation sensations” (Chrea et al. Their results clearly indicate that the proposed odor arrangements have varied considerably with respect to number and nature of olfactory dimensions. . However, these differences were mainly found in the assignment of single odors to classes. . Pierce 1999; Conway and Huffcutt 2003; Costello and Osborne 2005). Gottfried Nilsson . It affects 1) basic perceptual ratings as well as 2) odor classifications. However, both approaches are based on distinct mathematical assumptions even though often yield fairly similar results. Park Dravnieks To address this issue, we reviewed 28 perception-based classification studies and found that their outcome has been largely determined by 4 influencing factors: 1) interindividual differences in perceptual and verbal abilities of subjects, 2) stimuli characteristics, 3) approaches of data collection, and 4) methods of data analysis. Zarzo (2008b) and Zarzo and Stanton (2009) labeled a dimension feminine versus masculine that discriminated floral, fruity from earthy, dusty odors. S When comparing both approaches with respect to the aims of classification studies, conceptual assumptions as well empirical evidence argue for the application of EFA in classification studies (Gorsuch 1983, 1990; Widaman 1993; Fabrigar et al. T AN Unquestionably, the perceptual classes applied by odor professionals are acquired. Grandjean H C Subjects were asked to decide whether pairwise presented odors were identical. Hence, odor researchers are advised to control for basic sources of variability, namely age, gender, and culture, both in the recruitment of participants and the analysis of (group) data. EP 1968). The search for an adequate system has been a long one. 2004). D B D 2) Different from nonprofessionals, experts can give verbal descriptions for odors that are matched with an appropriate stimuli by other experts (Lawless 1984; Solomon 1990). 2006; Howard et al. . Kanaya Jones-Gotman Decoding the psychological dimensions of human odor perception has long been a central issue of olfactory research. Not surprisingly, neither an accepted system nor a reliable consensus on the basic principles of this arrangement has been reached. The results of almost 2.4 million panelists aged between 10 and 90 years point toward a change in odor quality perception with increasing age. Decoding the psychological dimensions of human odor perception has long been a central issue of olfactory research. A metric of 1664 structural characteristics smell 2. the act or function olfactory... 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