Difficulty in evoking odor images: The role of odor naming

Many studies report that people have difficulty in evoking odor images. In this article, we explore whether this results from another commonly observed phenomenon, difficulty in naming odors. In Experiment 1, participants both named and attempted to imagine either odors or their common visual referents. More-difficult-to-name odors were reported as being more difficult to evoke as olfactory images, in comparison with the visual condition. In Experiment 2, participants received training prior to forming odor images and naming the same set of odors. As in Experiment 1, more-difficult-to-name odors were harder to imagine, but participants who had learned the odor names during training were significantly better, by their own report, at imagining many of these stimuli, relative to participants who were either exposed to the odors, exposed to their names, or who received no pretraining. In sum, these experiments suggest that odor naming may account for some of the difficulty reported by participants when attempting to evoke odor images; we discuss an associative basis for this effect.     

Iranian Herbalists,But Not Cooks,Are Better at Naming Odors Than Laypeople

Odor naming is enhanced in communities where communication about odors is a central part of daily life (e.g., wine experts, flavorists, and some hunter‐gatherer groups). In this study, we investigated how expert knowledge and daily experience affect the ability to name odors in a group of experts that has not previously been investigated in this context—Iranian herbalists; also called attars—as well as cooks and laypeople. We assessed naming accuracy and consistency for 16 herb and spice odors, collected judgments of odor perception, and evaluated participants' odor meta‐awareness. Participants' responses were overall more consistent and accurate for more frequent and familiar odors. Moreover, attars were more accurate than both cooks and laypeople at naming odors, although cooks did not perform significantly better than laypeople. Attars' perceptual ratings of odors and their overall odor meta‐awareness suggest they are also more attuned to odors than the other two groups. To conclude, Iranian attars—but not cooks—are better odor namers than laypeople. They also have greater meta‐awareness and differential perceptual responses to odors. These findings further highlight the critical role that expertise and type of experience have on olfactory functions.     

Smelling what was there: Acquired olfactory percepts are resistant to further modification

Repeated exposure to a mixture of two odors can increase their perceived similarity to each other when presented separately. Experiment 1 failed to detect any reduction of this effect by an interference treatment consisting of separate exposures to the odors after they had first been presented as a mixture. Exposure to a mixture also results in participants mistakenly rating this mixture and its elements as having occurred with equal frequency (i.e., confusing the mixture and its elements). The interference treatment did not affect this either, whereas it did change judgments about the frequency of a color–odor mixture and its elements. The greater resistance to interference of odor–odor learning compared to color–odor learning may result from configural encoding of odor–odor mixtures. Experiment 2 found that separate exposures to two odors not previously mixed decreased their perceived similarity. This result was inconsistent with the possibility that the interference treatment in Experiment 1 had tended to increase the similarity of the two odors, for example, by a process of sensory adaptation. Rather it suggested a process akin to acquired distinctiveness.     

Odor from rats tasting a signal of illness

Rats running in a runway emit discriminable odors when encountering reward (R) or nonreward (N) goal events, and subsequent rats use these odors as discriminative stimuli to alter their approach speeds. In the present studies, a third goal event, aversively conditioned denatonium saccharide (A), was introduced. In Experiment 1, rats evidently emitted an odor when encountering the A goal event, because in the presence of this A odor subsequent conspecifics slowed their approach to the goal, much like their behavior on N trials. In Experiment 2, when N odor signaled R goal events and A odor signaled A goal events, rats approached quickly to N but slowly to A, indicating that they could discriminate N and A odors at the given concentrations. These studies indicate that rats emit an odor when confronted with a signal of impending illness and that this odor seems readily discriminable from R and N odors.     

Very long-term memory for odors: retention of odor-name associations.

The ability to remember odor-name associations for recent odors (those associated with everyday products experienced within the past 2 years) and distant odors (those associated with children's toys not encountered for 3 years or more) was examined in two experiments. In recognition tasks, subjects attempted to match odor names to odors, or odors to odor names. In a recall task, subjects tried to identify odors by name. The results showed that although odor retention was better for recent than distant odors, significant retention remains for odors not experienced since childhood. These results are consistent with other studies that found very slow and gradual loss of odor information in memory. They extend that research by showing that odor information is still available over a much longer period of time.     

Subliminal smells can guide social preferences

It is widely accepted that unconscious processes can modulate judgments and behavior, but do such influences affect one's daily interactions with other people? Given that olfactory information has relatively direct access to cortical and subcortical emotional circuits, we tested whether the affective content of subliminal odors alters social preferences. Participants rated the likeability of neutral faces after smelling pleasant, neutral, or unpleasant odors delivered below detection thresholds. Odor affect significantly shifted likeability ratings only for those participants lacking conscious awareness of the smells, as verified by chance-level trial-by-trial performance on an odor-detection task. Across participants, the magnitude of this priming effect decreased as sensitivity for odor detection increased. In contrast, heart rate responses tracked odor valence independently of odor awareness. These results indicate that social preferences are subject to influences from odors that escape awareness, whereas the availability of conscious odor information may disrupt such effects.     

Similarity in the qualities of individual odors among kin and species in Turkish (Mesocricetus brandti) and golden (Mesocricetus auratus) hamsters.

In this investigation, the authors used habituation techniques to explore similarities and differences in the qualities of individual odors from hamsters. In Experiment 1, male Turkish hamsters (Mesocricetus brandti) treated flank-gland odors of 2 males from 1 litter as similar compared with the odor of a male from another litter, whether the odor donors were familiar or unfamiliar. At the same time, the Turkish hamsters discriminated between the subtle differences in the individual odors of their familiar brothers. In Experiment 2, male Turkish and golden hamsters (Mesocricetus auratus) treated the flank-gland odors of 2 unfamiliar, unrelated conspecifics as similar compared with the flank odor of a heterospecific individual. The results suggest that similarities in individual odors are related to genetic similarity of the odor donors. These similarities could provide a basis for different types of social recognition, including kin and species recognition.     

Implicit and explicit tests of odor memory reveal different outcomes following interference

Experiencing two odors as a mixture can later increase their perceived similarity when presented separately. Such an increase in similarity can be used as an implicit measure of how well participants remember the mixture. Three experiments tested the resistance to interference of this effect by first giving participants exposure to two 2-odor mixtures and then presenting each odor from one mixture (interfered pair) separately many times. After the latter interference phase, participants rated the similarity of the two odors in each pair. The experiments varied in terms of the number of initial exposures to the mixtures, the number of odor presentations in the interference phase, and the control conditions employed. No difference in similarity ratings for the interfered and non-interfered pair was found in any experiment. In contrast to the lack of interference with this implicit measure, an explicit measure of memory based on participants’ ratings of odor frequency revealed that they could recall to some degree that the interfered odors had been presented alone in the second phase. These results suggest that implicit memory for odor mixtures is highly resistant to interference and is consistent with a configural encoding account of this effect.     

Perceptual learning with odors: implications for psychological accounts of odor quality perception

After two odors have been experienced in a mixture, the pair are subsequently rated as sharing more qualities and smelling more alike than equally exposed controls. These effects may result from the retrieval of a common mixture memory when either component is sniffed alone. If correct, odor pairs experienced together in a mixture should also be less discriminable than those experienced an equal number of times but in different mixtures. This was tested here by exposing participants to two odor mixtures (either AX, BY or AY, BX) and then testing their ability to discriminate between the components. As predicted, odors previously experienced together as a mixture were less discriminable than controls. These and related findings noted above suggest that learning and memory play an important role in odor quality perception.     

The influence of verbal labeling on the perception of odors: evidence for olfactory illusions?

Using the definition that an illusion is observed when a stimulus is invariant but context alters its perception, we examined whether verbal context could produce olfactory illusions. To test this effect, we chose five odors with minimally fixed sources and that could be interpreted with various hedonic connotations. The odors were violet leaf, patchouli, pine oil, menthol, and a 1:1 mixture of isovaleric and butyric acids. Subjects individually sniffed each odor at two different sessions separated by one week. At each session an odor was given a different verbal label (either positive or negative) and subjects rated the odors on several hedonic scales and provided perceptual and interpretative responses to them. Results showed that the perception of an odor could be significantly influenced by the label provided for it. We propose that the cases where verbal labels inverted odor perception are the first empirical demonstrations of olfactory illusions.     

Pain tolerance selectively increased by a sweet-smelling odor

The mechanism underlying reported analgesic effects of odors in humans is unclear, although odor hedonics has been implicated. We tested whether odors that are sweet smelling through prior association with tasted sweetness might influence pain by activating the same analgesic mechanisms as sweet tastes. Inhalation of a sweet-smelling odor during a cold-pressor test increased tolerance for pain compared with inhalation of pleasant and unpleasant low-sweetness odors and no odor. There were no significant differences in pain ratings among the odor conditions. These results suggest that smelled sweetness can produce a naturally occurring conditioned increase in pain tolerance.     

Proust nose best: Odors are better cues of autobiographical memory

The Proust phenomenon is an enduring piece of folk wisdom that asserts that odors are particularly powerful autobiographical memory cues. We provide a more formal exposition of this phenomenon and test it in two experiments, using a novel double-cuing methodology designed to negate less interesting explanations. In both studies, recall of an autobiographical event was initially cued by a verbal label (an odor name) for a fixed period, following which a second, extended recall attempt was cued by the same verbal label, the relevant odor, an irrelevant odor, or a visual cue. The focus of Experiment 1 was participants' ratings of the emotional quality of their autobiographical memories. In Experiment 2, content analysis was employed to determine the quantity of information in participants' recollections. Results revealed that odor-cued autobiographical memories were reliably different in terms of qualitative ratings and reliably superior in the amount of detail yielded. Moreover, visual cues and incongruent olfactory cues appeared to have a detrimental effect on the amount of detail recalled. These results support the proposal that odors are especially effective as reminders of past experience.     

The influence of chemical complexity on the perception of multicomponent odor mixtures

The present study investigates the hypothesis that complexobject 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.     

AUDITORY PITCH AS A PERCEPTUAL ANALOGUE TO ODOR QUALITY

Abstract— Experiments in cross-modal matching suggest that smells can be arranged by odor qualify along the color dimensions of hue and lightness. Here we report that subjects readily adjust the loudness-equalized pitch of on auditory tone to match a stimulus odor. The results allow odors to be arranged in sequence by their pitch-equivalents. The tone matches appear to be based on perceptual feature of olfaction other than stimulus intensity or pleasantness. The results suggest that features of odor quality may be more accessible and structured than previously acknowledged.     

Recognition of odors and identification of sources

The purpose of the present study was to investigate the accuracy of the memory for odors and for the location of odors. In Experiment 1, 5 unfamiliar odors were presented in each of 2 rooms. Twenty participants were instructed to remember only the odors (odor-only control group) and 20 were instructed to remember both the odors and the room where the odors were presented (odor place group). In Experiment 2, both the odor presentation room and the sex of the experimenters were manipulated to increase the uniqueness of the odor location. The results demonstrated that the memory for an odor is superior to the memory for the location of an odor. The results also indicated that the intention to learn the sources of an odor improves the memory for the source. These results are discussed in the context of the source monitoring framework.     

The Sound of Smell: Associating Odor Valence With Disgust Sounds

Olfaction has recently been highlighted as a sense poorly connected with language. Odor is difficult to verbalize, and it has few qualities that afford mimicry by vision or sound. At the same time, emotion is thought to be the most salient dimension of an odor, and it could therefore be an olfactory dimension more easily communicated. We investigated whether sounds imitative of an innate disgust response can be associated with unpleasant odors. In two experiments, participants were asked to make a forced choice between a pseudoword including a disgust sound and a neutral pseudoword, for pleasant and unpleasant odors. Overall, participants chose more disgust pseudowords than neutral pseudowords for unpleasant odors, but this was not the case for pleasant odors. This effect was not driven by a general association between unpleasant sounds and unpleasant odors, but specifically the sounds [x/χ] and [f], thought to reflect physical responses to disgusting odors, as seen in the Polish fu! or the English ugh!. In line with growing evidence that language can encode odor, we provide the first experimental evidence for an association between the sound of a word and odor valence.     

Categorizing Smells: A Localist Approach

Humans are poorer at identifying smells and communicating about them, compared to other sensory domains. They also cannot easily organize odor sensations in a general conceptual space, where geometric distance could represent how similar or different all odors are. These two generalities are more or less accepted by psychologists, and they are often seen as connected: If there is no conceptual space for odors, then olfactory identification should indeed be poor. We propose here an important revision to this conclusion: We believe that the claim that there is no odor space is true only if by odor space, one means a conceptual space representing all possible odor sensations, in the paradigmatic sense used for instance for color. However, in a less paradigmatic sense, local conceptual spaces representing a given subset of odors do exist. Thus the absence of a global odor space does not warrant the conclusion that there is no olfactory conceptual map at all. Here we show how a localist account provides a new interpretation of experts and cross-cultural categorization studies: Rather than being exceptions to the poor olfactory identification and communication usually seen elsewhere, experts and cross-cultural categorization are here taken to corroborate the existence of local conceptual spaces.     

The role of the dorsal and ventral hippocampus in olfactory working memory

Olfactory working memory and pattern separation for odor information was assessed in male rats using a matching-to-sample for odors paradigm. The odor set consisted of a five aliphatic acids with unbranched carbon chains that varied from two- to six-carbons in length. Each trial consisted of a sample phase followed by a choice phase. During the sample phase, rats would receive one of five different odors. Fifteen seconds later during the choice phase one of the previous odors was presented simultaneously side by side with a different odor that was based on the number of aliphatic acids that varied in the carbon chains from two- to six-carbons in length and rats were allowed to choose between the two odors. The rule to be learned in order to receive a food reward was to always choose the odor that occurred during the study phase. Odor separations of 1, 2, 3 or 4 were selected for each choice phase and represented the carbon chain difference between the study phase odor and the test phase odor. Once an animal reached a criterion of 80–90% correct across all temporal separations based on 40 trials, rats received a control, dorsal hippocampal, or ventral hippocampal lesion and were retested on the task. On postoperative trials, only the ventral hippocampal lesion group was impaired relative to both control and dorsal hippocampal groups groups. There were no effects on odor pattern separation. All groups of rats could discriminate between the odors. The data suggest that the ventral hippocampus, but not dorsal hippocampus, supports working memory for odor information.     

Influence of color on odor identification and liking ratings.

The effects of color on odor identification were tested under color appropriate, inappropriate, and blindfolded conditions. Subjects made fewer errors in identifying solutions that were colored appropriately (e.g., red-cherry) than in either the blindfolded condition, where there were no color cues, or the inappropriate color condition (e.g., red-lemon). Identification accuracy was greatest for typical odor-color combinations (e.g., red-cherry) compared with appropriate but nontypical odor-color combinations (e.g., red-watermelon). Response latencies were fastest for odors in the appropriately colored solutions. Subjects also rated appropriate color-odor combinations as most pleasant. However, this effect is probably due to the increase in identification accuracy of the appropriately colored solutions. In all three conditions, correctly identified odors were liked more than odors that were not correctly identified. Thus, color is an important perceptual variable in odor identification because it biases subjects toward a color category that facilitates identification if the color is "correct". This ability to identify an odor in turn influences the affective response to the odor.