Demographic and cognitive predictors of cued odor identification: evidence from a population-based study

This study investigated demographic and cognitive correlates of cued odor identification in a population-based sample from the Betula project: 1906 healthy adults varying in age from 45 to 90 years were assessed in a number of tasks tapping various cognitive domains, including cognitive speed, semantic memory and executive functioning. The results revealed a gradual and linear deterioration in cued odor identification across the adult life span. Overall, females identified more odors than men, although men and women performed at the same level in the oldest age cohort (85-90 years). Hierarchical regression analyses revealed that age, sex, education, cognitive speed and vocabulary were reliable correlates of performance in the odor identification task. In addition, age-related deficits in the included demographic and cognitive variables could not fully account for the observed age-related impairment in identification, suggesting that additional factors are underlying the observed deterioration. Likely candidates here are sensory abilities such as olfactory detection and discrimination.     

A metamemory perspective on odor naming and identification

A metacognitive perspective is utilized to elucidate why it is so difficult to name common odors and what characterizes the subjective knowledge people have about their actual odor knowledge. Odor-naming failures are often accompanied by strong feelings of knowing (FOK) or feelings of imminent retrieval of what it is that smells. The paper's two experiments investigate FOK judgements and tip of the tongue (TOT) experiences for odor and person names. The data indicate that our inability to correctly name odors are typically not due to the often proposed uniquely poor association between odors and their proper names, but rather due to failures to identify the odors, that is, failures to know 'what it is'. It was also found that (i) TOT experiences are very unusual for odor names and more so than for person names; (ii) FOK judgements about odor names are significantly less predictive of later retrieval than equivalent judgements about names of persons; (iii) FOK judgements were highly correlated with the familiarity of the cue (odor or picture of famous person), rendering some support for the idea that FOK judgements are based on the perceived familiarity of the cue triggering the FOK; and (iv) the idea that FOK judgements are based on the amount of available information about the sought-for memory (accessibility theory) was also supported.     

Odor recognition memory as a function of odor-naming performance

A series of experiments sought to clarify the relationship between odor naming and memory by manipulating odor label availability during a dual naming-memory task. Experiment 1 demonstrated that recognition memory and odor naming were both better when the naming task provided participants with odor label alternatives. Consistent and correct odor naming was associated with nearly perfect memory, whereas inconsistent or incorrect naming was associated with very weak memory if any at all. Experiment 2 showed that the availability of odor labels was effective at improving memory only if labels were available at both memory encoding and retrieval, suggesting that the labels were aiding memory by improving the identification of the odors. Odor naming was manipulated in Experiment 3 by varying the number of available labels from 4 to 16 during each odor-naming trial. As found in the previous experiments, naming and memory were strongly related in each of the labeling conditions. Experiment 4 showed that corrective naming feedback produced better memory performance but only when the feedback led to correct odor naming. It was concluded that perceptual processes related to matching olfactory input to acquired, multidimensional representations of odors play a critical role in both odor naming and episodic memory.     

Odor identification by males and females: predictions vs performance

More than 200 males and females estimated the identifiabilityof 80 common odorous objects (e.g., chocolate, beer, mustard,rubber). The two genders agreed rather closely in their estimates.The groups also agreed closely in their relative judgementsof whether males or females could identify the objects better.Both groups anticipated that males would be superior for onlya small number of substances, mainly substances that seem stereotypically‘male’ (e.g., cigar butts, beer, machine oil). Thegroups anticipated female superiority for not only stereotypically‘female’ substances (e.g., Ivory soap, Johnson'sbaby powder, nail polish remover), but also for virtually allfoods, including foods presumably consumed equally by both sexes(e.g., potato chips, Juicy Fruit gum, grape drink). The resultssuggested the existence of a second stereotype, namely thatfemales will be superior at identifying all substances not clearlyin the male domain. An experiment that explored the performanceof 46 males and females over five sessions revealed generalfemale superiority. The superiority extended to odors considered‘male’. Males seemed educable and could apparentlyovercome their disadvantage eventually with merely some helpin the retrieval of odor names. Blockage of retrieval seemsa strong limiting factor in odor identification for femalesas well as for males. Irrespective of gender, when persons havethe veridical name of a well-known odor made available by oneor another means, they exhibit considerable talent at identifyingobjects by smell. ¹Supported by NIH Grant ES 00592     

Odor emotionality affects the confidence in odor naming

Previous research has demonstrated that participants are overconfident in the veracity of their odor identifications. This means that their confidence expressed as subjective probabilities is, on average, higher than the actual proportion of correct odor identifications. The current experiment tested the hypothesis that the more arousing an odor is, the more participants are overconfident in their identification of it. The results indicated that part of the overconfidence in odor identification can, indeed, be due to the arousing properties of the odors. This suggests that emotional variables should be taken into account when researching metamemory.     

New evidence that the MHC influences odor perception in humans: a study with 58 Southern Brazilian students

Increasing evidence suggests a correlation between mate choice, odor preference, and genetic similarity at the Major Histocompatibility Complex (MHC) in a variety of animals, including our species. The MHC is a highly polymorphic group of genes that play an important role in the immunological self/nonself recognition. Its products have been reported to take part on the variety of compounds and reactions that together build an individual's body odor. It has been suggested, therefore, that animals use body odor as a guide to identify possible mates as MHC-similar or MHC-dissimilar from their own genotype. Preference for a MHC-dissimilar partner enhances MHC heterozygosity of an individual's offspring. The possible adaptive advantages are clear: it is a mechanism of avoiding inbreeding and MHC-heterozygous offspring may have enhanced immunocompetence. The aim of this study was to search, in our species, new evidence on the correlation between specificities at HLA-A and HLA-B and assessments of pleasantness regarding specific body odors. HLA is the name for the human MHC. Four olfactory sessions were performed with 58 young Southern Brazilian students, in order to investigate whether assessments of pleasantness of body odors from individuals correlate to a person's HLA phenotype. Body odors were collected via sweat and urine from all participants. Women smelled and scored all male odor samples and men did the same with all female samples. We found a significant correlation only when female smellers evaluated male sweat odors.     

Olfactory metacognition

The current paper focuses on the subjective knowledge people have about their ability to name odors. Previous investigations of such metacognitive aspects of olfactory cognition are very scarce and have yielded results that need further scrutiny. In two experiments, we investigated three metamemory judgments about odor identity. As opposed to previous findings, participants' feeling of knowing judgments about odor identity predicted later recognition. Participants were also accurate but highly overconfident in their retrospective confidence in odor identification. A strong and imminent feeling of being able to name an odor, a so-called 'tip of the nose' experience, was found to predict later recall, but was otherwise poorly related to any partial activation of the odor name or other information associated with the odor. This makes it different from the commonly investigated 'tip of the tongue' phenomenon. The current study shows that olfactory metamemory is related to actual knowledge, a finding that is in line with what has been observed for other modalities.     

Effects of perceived and imagined odors on taste detection

We assessed the influence of different odors on detection of a sweet tastant, and the ability of imagined odors to elicit the same effects as perceived odors on taste perception. The tastant used was sucrose, and the two odorants were strawberry and ham. In the first experiment, participants either smelled or imagined one of two odors during taste detection tasks (between-subject design), whereas in the second one, subjects completed both the odor imagery and perception conditions with taste detection tasks (within-subject design). The effect was odorant-specific: detection of sucrose was significantly better when subjects smelled strawberry than when they smelled ham. Furthermore, imagined odors influenced taste perception in the same way as did perceived odors. We concluded that the odor-specific effect on taste perception is an authentic perceptual phenomenon. Our results also support the notion that odor-induced changes in taste perception are mediated centrally. Finally, our findings are in agreement with reports supporting the existence of odor imagery.     

Chemosensory cross-modal stroop effects: congruent odors facilitate taste identification

In order to explore the cross-modal cognitive associations between smell and taste, a chemosensory analogue of the Stroop task (Stroop 1935) was developed. Fourteen participants were presented with an odorant and a tastant and asked to identify the tastant as "sweet" or "sour" by pressing 1 of 2 buttons as quickly as possible. Participants were faster to name the taste when it was presented with an odor that was congruent (e.g., strawberry/sweet) than with an incongruent odor (e.g., strawberry/sour). These results support the concept of a high level of cognitive integration between the senses of smell and taste and illustrates occasions of interference between information arising from different sensory systems.     

The kinological identification of individual scents in the traces of the vital activities of 4 vertebrate species

One can successfully identify individual odors of almost any terrestrial vertebrates using laboratory dogs. The excretions can be collected on adsorbent paper and conserved for subsequent identification. It has been experimentally shown that the odor of house mice remains stable during the whole life span and that the stabilization of dog-identifiable odors finishes in young mice at 14 day. The method tested will allow to create individual banks of animal odors, e.g. for identification of rare species.     

Odor Valence Linearly Modulates Attractiveness,but Not Age Assessment,of Invariant Facial Features in a Memory-Based Rating Task

Scented cosmetic products are used across cultures as a way to favorably influence one''s appearance. While crossmodal effects of odor valence on perceived attractiveness of facial features have been demonstrated experimentally, it is unknown whether they represent a phenomenon specific to affective processing. In this experiment, we presented odors in the context of a face battery with systematic feature manipulations during a speeded response task. Modulatory effects of linear increases of odor valence were investigated by juxtaposing subsequent memory-based ratings tasks – one predominantly affective (attractiveness) and a second, cognitive (age). The linear modulation pattern observed for attractiveness was consistent with additive effects of face and odor appraisal. Effects of odor valence on age perception were not linearly modulated and may be the result of cognitive interference. Affective and cognitive processing of faces thus appear to differ in their susceptibility to modulation by odors, likely as a result of privileged access of olfactory stimuli to affective brain networks. These results are critically discussed with respect to potential biases introduced by the preceding speeded response task.     

Development of a smell identification test using a novel stick-type odor presentation kit

The odor identification is strongly influenced by the social and cultural factors; therefore, the odorants used in a smell identification test should be familiar to the test population. In addition, the device used in the test is desired to be simply handled and retain odor quality over time. We developed a novel stick-type odor presentation kit that consists of microcapsules of odorant incorporated into stable cream and the smell identification test using it. Thirteen odorants were selected to be familiar to the test population. In the test, we used two identification methods: one was a modified forced-choice paradigm with "detectable but not recognizable" and "no smell detected" added as choices and the other was a two-step identification paradigm where the participant first selected one of eight odor categories and then chose the specific odor name from the selected category. We verified the performance of the odor stick and the test by stability, using a test-retest paradigm, comparing this test with another smell test, and testing Japanese people from a range of age groups. We conclude that this kit is a useful odor presentation device, and the test using it works effectively as a smell identification test.     

Measures of human olfactory perception during pregnancy

Although considerable anecdotal evidence suggests that pregnancy affects olfactory sensitivity, scientific evidence is limited and inconclusive. Whereas hedonic ratings are affected by pregnancy, odor identification is not. The aim of the current study was to examine odor perception in women across pregnancy and in the postpartum period. One hundred nonsmoking women who were pregnant, postpartum, or had never been pregnant were tested on the University of Pennsylvania Smell Identification Test (UPSIT). Intensity ratings and scratch patterns were collected as potential indicators of sensitivity, and participants rated the odors' pleasantness. Participants also rated their own sense of smell. Mean UPSIT scores did not differ significantly across groups indicating no difference in odor identification. Trends in planned comparisons suggested that in the first trimester, odors were rated as more intense and less pleasant. In the first trimester, women scratched the odor strips significantly fewer times. Consistent with previous reports, 90% of pregnant women reported that specific odors smelled less pleasant and 60% reported that some odors smelled more pleasant. Although nearly two-thirds of pregnant women rated their olfactory sensitivity to be enhanced during pregnancy and overall pregnant women's self-rated olfactory sensitivity was higher than controls', self-ratings were not correlated with UPSIT scores nor odor intensity ratings. These results suggest that these and previous findings may reflect the fact that the effect of pregnancy on olfaction is small and inconsistent.     

Olfactory cues modulate facial attractiveness

We report an experiment designed to investigate whether olfactory cues can influence people's judgments of facial attractiveness. Sixteen female participants judged the attractiveness of a series of male faces presented briefly on a computer monitor using a 9-point visual rating scale. While viewing each face, the participants were simultaneously presented with either clean air or else with 1 of 4 odorants (the odor was varied on a trial-by-trial basis) from a custom-built olfactometer. We included 2 pleasant odors (geranium and a male fragrance) and 2 unpleasant odors (rubber and body odor) as confirmed by pilot testing. The results showed that the participants rated the male faces as being significantly less attractive in the presence of an unpleasant odor than when the faces were presented together with a pleasant odor or with clean air (these conditions did not differ significantly). These results demonstrate the cross-modal influence that unpleasant odors can have on people's judgments of facial attractiveness. Interestingly, this pattern of results was unaffected by whether the odors were body relevant (the body odor and the male fragrance) or not (the rubber and geranium odors).     

Olfactory conditioning of positive performance in humans

Olfactory conditioning effects have been widely demonstrated in the animal literature but more seldom in human populations and rarely of consciously controlled human behaviors. Building upon previous work on negative performance, we report the first experimental evidence that odors can be used effectively in a classical conditioning paradigm to positively influence human behavior. In the present study, underachieving schoolchildren experienced unexpected success at a paper-and-pencil task in the presence of an ambient odor. When they later experienced the same odor again, performance on other tasks was superior to that of relevant control groups. These data substantially extend previous results on human olfactory classical conditioning and show that odors potentially can be used to exert positive influences on human behavior.     

Some effects of aphasic lesions on order perception.

Twenty-four aphasic, nine brain-damaged, and eight non-brain-damaged patients were tested for their ability to associate odors with visual targets. The results of the experiment show that lesions producing aphasia interfere with the ability to match an odor to a directly corresponding visual target. As aphasics with anterior and posterior lesions performed at similar levels in this task, it was not possible to conclude that the observed deficits were specifically related to temporal lobe functions. The severity of the deficit was greater for more massively lesioned aphasics. The exact nature of the deficit was not clear, but review of the literature and differential results obtained for the two experimental tasks suggest that aphasic lesions may interefere with odor identification.     

Implicit learning and implicit memory for odors: the influence of odor identification and retention time

One hundred and fifty-two subjects, divided into eight groups, were exposed to a room with a low concentration of either orange or lavender and to an odorless room. In a careful double-blind procedure, neither the subjects nor the experimenters were made aware of the presence of the odors in the experimental conditions. Later they were asked to indicate how well each of 12 odor stimuli, including the experimental and control odors, befitted each of 12 visual contexts, including the exposure rooms. At the end of this session they rated the pleasantness and the familiarity of the odors, and identified them by name. Finally they were debriefed and asked specifically whether they had perceived the experimental odors anywhere in the building. The results of four subjects who answered positively to the latter question were omitted. The results confirm the earlier finding that non-identifiers implicitly link odor and exposure room, whereas identifiers do not show such a link. It is suggested that episodic information is an essential constituent of olfactory memory and that its function is comparable to that of form and structure in visual and auditory memory systems.     

Odors: implicit memory and performance effects.

In order to assess the influence of odors on human performance and implicit memory for odors, 108 subjects completed a variety of tests in weakly scented (jasmine, lavender or odorless) rooms without having been made aware of the odor. After a 30 min interval the subjects were shown slides of different surroundings, including the room they had been in, and were requested to rate how well a set of 12 odors, including a blank, would fit to these surroundings. Half of these contexts contained visual cues related to two of the presented odors (leather and coffee). After the rating of fit the subjects had to rate the odors for pleasantness, were asked to identify the odors with their correct names and to tell where and when they had last smelled these odors. One subject remembered smelling the odor (jasmine) in the room and was discarded from the analysis of the results for the rating of fit. None of the others reported recollection of the experimental odors. The results showed that in general jasmine had a negative and lavender a positive effect on test performance. If an odor-related visual cue was present in the context, the related odor was always rated highest in fit to that context. Furthermore, the subjects working in rooms with an odor subsequently assigned this odor to the visual context of that room to a significantly higher degree than subjects working in rooms with different odors. Since none of the subjects reported that they had smelled the odor in the rooms where performance testing took place, it was concluded that the memory for these odors was implicit. Further analysis showed that such memory was only found in subjects who were unable to supply the right name for the odor. The possible consequences of this latter finding for understanding the relationship between sensory (episodic) and semantic odor memory are discussed.