The capacity of humans to identify components in complex odor-taste mixtures. Chem. Senses 31:539–545 (original) (raw)
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In flavor perception, both experience with the components of odor/taste mixtures and the cognitive strategy used to examine the interactions between the components influence the overall mixture perception. However, the effect of these factors on odor mixtures perception has never been studied. The present study aimed at evaluating whether 1) previous exposure to the odorants included in a mixture or 2) the synthetic or analytic strategy engaged during odorants mixture evaluation determines odor representation. Blending mixtures, in which subjects perceived a unique quality distinct from those of components, were chosen in order to induce a priori synthetic perception. In the first part, we checked whether the chosen mixtures presented blending properties for our subjects. In the second part, 3 groups of participants were either exposed to the odorants contributing to blending mixtures with a ''pineapple'' or a ''red cordial'' odor or nonexposed. In a following task, half of each group was assigned to a synthetic or an analytical task. The synthetic task consisted of rating how typical (i.e., representative) of the target odor name (pineapple or red cordial) were the mixtures and each of their components. The analytical task consisted of evaluating these stimuli on several scales labeled with the target odor name and odor descriptors of the components. Previous exposure to mixture components was found to decrease mixture typicality but only for the pineapple blending mixture. Likewise, subjects engaged in an analytical task rated both blending mixtures as less typical than did subjects engaged in a synthetic task. This study supports a conclusion that odor mixtures can be perceived either analytically or synthetically according to the cognitive strategy engaged.
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The present study investigates the hypothesis that complex object odors (odors that emanate from flowers, foods, sewage, etc.) that consist of dozens of odorants are processed and encoded as discrete entities, as if each was a single chemical odor. To test this hypothesis, the capacity of trained subjects to discriminate and identify the components of stimuli consisting of one to eight object odors was determined. The results indicated that subjects could only identify up to four object odors in a mixture, which is similar to earlier findings with mixtures that contained only single chemical odors. The limited capacity was also reflected in the number of odors selected, regardless of whether the choices were correct or incorrect, in confidence ratings, and in decision times. The identification of a limited number of object odors in every mixture that was presented suggests that both associative (synthetic) and dissociative (analytic) processes are involved in the perceptual analysis of odor mixtures.
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Perceptions of the flavors of foods or beverages reflect information derived from multiple sensory afferents, including gustatory, olfactory, and somatosensory fibers. Although flavor perception therefore arises from the central integration of multiple sensory inputs, it is possible to distinguish the different modalities contributing to flavor, especially when attention is drawn to particular sensory characteristics. Nevertheless, our experiences of the flavor of a food or beverage are also simultaneously of an overall unitary perception. Research aimed at understanding the mechanisms behind this integrated flavor perception is, for the most part, relatively recent. However, psychophysical, neuroimaging and neurophysiological studies on cross-modal sensory interactions involved in flavor perception have started to provide an understanding of the integrated activity of sensory systems that generate such unitary perceptions, and hence the mechanisms by which these signals are functionally united when anatomically separated . Here we review this recent research on odor/taste integration, and propose a model of flavor processing that depends on prior experience with the particular combination of sensory inputs, temporal and spatial concurrence, and attentional allocation. We propose that flavor perception depends upon neural processes occurring in chemosensory regions of the brain, including the anterior insula, frontal operculum, orbitofrontal cortex and anterior cingulate cortex, as well as upon the interaction of this chemosensory flavor network with other heteromodal regions including the posterior parietal cortex and possibly the ventral lateral prefrontal cortex.
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Certain odors are routinely described as smelling sweet, This phenomenon may result from the co-occurrence of such odors and tastes outside the laboratory. Experiment 1 tested this possibility by pairing a selected odor with sucrose and another with citric acid in a masked design, using 24-h spaced sessions, preceded and followed by ratings of the odors' taste attributes when sniffed and when rated with tastes in solution. Following conditioning, the odor paired with sucrose smelled sweeter and with citric acid, sourer. In Experiment 2, contingency awareness was examined using a recognition measure, in an otherwise similar design. Again, odors smelled sweeter and sourer postconditioning. Contingency aware and unaware subjects did not differ in performance. Experiment 3 examined an exposure account of these changes, using a similar paradigm to Experiment 1, but with no exposures to sucrose or citric acid. No changes in odor taste attributes were observed. Overall, these findings demonstrate that associative learning, irrespective of awareness, has an important role in tile acquisition of odor-taste qualities.
Selective attention and the perceptual analysis of odor mixtures
Physiology & behavior, 1992
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Perception & Psychophysics, 1982
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Learning Influences the Perception of Odor Mixtures
In this study, we investigated the influence of semantic and perceptual learning on the perception of odor blending mixtures, i.e., mixtures eliciting a different odor quality as compared with their components. Following a between-groups design, we set out to examine whether being pre-exposed to target mixture odor labels (semantic learning) and to the mixture's odor components (perceptual olfactory learning) would modify the perception of odor mixtures quality. In a first experimental condition, a group (control) of 28 subjects evaluated the odor quality of mixtures and then their components. In this condition, subjects were not exposed to the individual odor components (no perceptual learning) and were only weakly exposed to the target mixture odor labels (weak semantic learning) when asked to evaluate the quality of the mixtures. In a second experimental condition, a group (learning) of 29 other subjects performed the same tasks but evaluated first the components and then the mixtures. In this condition, subjects have experienced both perceptual and strong semantic learning when asked to evaluate the quality of the mixtures. Within each condition, odor quality was evaluated following two verbal tasks: a free description task and a choice between several odor attributes. The comparison of the data obtained in both experimental conditions revealed that semantic and perceptual learning could influence odor mixture quality and suggested a differential influence of both learning types according to mixture complexity.
Behavioural Processes, 2003
Odours are judged to smell sweeter following simultaneous oral pairings with the tastant sucrose and sourer after parings with the tastant citric acid. This effect may result from human participants perceiving and encoding a unitary odour-taste percept. This study examined two factors thought likely to disrupt such encoding; (a) preexposure to the mixture elements and (b) training to spot the elements of taste-odour mixtures. Half of the participants were trained to identify tastes and smells and half received no training. All participants were preexposed to two odours (A, B) and two tastes (X, Y), followed by pairings of these stimuli (AX, BY) and then by pairings between two non-preexposed odours and the same tastes (CX, DY). This process was then repeated on a second session. Odour-taste learning was retarded following preexposure, but was unaffected by training. These findings suggest; (1) that odour-taste mixtures may be cognitively impenetrable and (2) that preexposure leads to encoding of A and B, which are then resistant to interference when further pairings are presented (i.e. AX, BY).