An interaction model for odor quality and intensity

Abstract

The perceived intensity and quality of binary odor mixtures are studied in relation to how their components are perceived when presented separately. Subjects judged the perceived intensity and quality of 6 concentrations of pyridine, 6 concentrations of n-butanol, and their 36 possible combinations. The results show that the perceived intensity ofthe mixture can be predicted from the perceived intensity of its components presented separately (R A and R B ) by the Euclidian arithmetic model. The maximum probability of identifying a mixture as a "mixture" is reached when R A and RB are equally strong. An interaction model for mixtures that relates perceived intensity and quality is presented and tested. The test reveals that both the perceived intensity of a mixture and the probability that it will be identified as the one or the other component can, by a simple interaction model, be successfully predicted from RA and RB• What do we perceive when more than one odorant is presented at the same time? Around the turn of the century, this question became quite controversial due to the substantial contributions of Zwaardemaker (1895, 1900/1959, 1907, 1930; for a review, see Olsson, 1993). He advocated that the mixture of two suprathreshold odors, even quite strong ones, are able to suppress each other to an odorless mixture when they are mixed in certain proportions. Zwaardemaker argued that this phenomenon, which he called compensation, was the olfactory analogue to how complementary colors form white light when different wavelengths are combined. However, several authors questioned the existence of compensation (e.g., Henning, 1924Henning, , 1926Nagel, 1897; Skramlik, 1926).Several decades later, attention was again given to odorquality interaction. The related question of whether the components are perceived in the mixture or form a new odor was revived. It has now been investigated with a number of methods, some of which imply different definitions of the problem, and the results have been diverse (e.g., Jellinek & Koster, 1979;Laing & Francis, 1989; Mitchell & McBride, 1971;Moskowitz & Barbe, 1977; Schiet & Frijters, 1988;Schwartz, Rabin, & Cain, 1987). Independent of the type of mixture percept, the mixture quality frequently seems to be intermediate to the quality of its component odors when presented separately (Ekman & Engen, 1962;Gregson, 1980;Moskowitz, 1976;Moskowitz & Barbe, 1977 Typically, the hedonic value of an odor emerges in the first dimension of the odor space as revealed in a multidimensional scaling experiment, and it may be the most salient attribute of odors (B. Berglund, U. Berglund, Engen, & Ekman, 1973;Moskowitz, 1976;Moskowitz & Barbe, 1977;Woskow, 1968). In accordance with the perceived quality of odor mixtures, their hedonic value is also found to be intermediate to their components (Lawless, 1977;Spence & Guilford, 1933;Lawless, 1977; cf. Dravnieks & Jarke, 1980).With progress in the abilities to scale odor intensity directly, a number of studies have described the quantitative princ...

Chemosensory Detectability of 1-Butanol and 2-Heptanone Singly and in Binary Mixtures

“…This holds for all three sensory enpoints: odor, nasal pungency, and eye irritation. The present data for smell, seen in the context of the commonly observed hypoadditivity of responses at suprathreshold levels, suggests that peri-threshold stimulation might elicit little or no mutual inhibition between components of a mixture (11,28). At levels progressively above threshold, an inhibitory interaction appears to grow.…”

“…In each session, the subject (26)), fish (e.g., (22)), and mammals (e.g., (5)), including primates (e.g., (24) Human studies of odor mixtures have largely focused on suprathreshold intensity (e.g., (8,28)) and quality discrimination (e.g., (25)). Considerably less attention has been paid to studies of thresholds for mixtures and for their components (see, for example, (17)).…”

Characteristic component odors emerge from mixtures after selective adaptation

“…We are uncertain whether this difference reflects fundamental differences in trigeminal and olfactory adaptation/identification [59] or slight mismatches in stimulus intensity, distinctiveness or familiarity. Nonetheless, identification of odors of the four component compounds all showed similar improvement after selective adaptation, providing evidence for analytical processing of odors not available from other experimental paradigms [25,26,56,63].…”

“…Consistent with mixture suppression, odors of many common foods and fragrances appear to be dominated by notes of single compounds that impart characteristic, albeit crude, identities [20,25,26,61]. Because odor-component identification is suppressed in mixtures [44,45,46], we surmise that olfactory notes originate from very few components that dominate odors of mixtures due to their relative strength at a given point in time [39,56]. "Top note," "middle note" and "bottom note" [62] are terms used to specify the timing of successive odors emerging from fragrant stimulus mixtures.…”

Chemesthesis from volatile organic compounds: Psychophysical and neural responses

“…We speculate that systematic variation in slope arises from the diversity of olfactory receptors stimulated by even a single VOC. The perception of mixtures offers potential insight here [42,43]; the more complex a mixture, the more compression, or mutual suppression of components, will it exhibit [44,45], presumably because more complex mixtures stimulate wider varieties of receptors. The outputs from different receptor neurons most likely exhibit mutual inhibition upstream [46,47].…”