Working memory (WM) processes are assumed to operate on a wide variety of sensory materials, yet WM research rarely extends beyond sight and hearing. In this systematic review, we integrate research from studies that address WM in olfaction, the sense of smell, spanning the last 50 yr (N = 44). We assessed whether 21 proposed benchmarks for WM generalize to olfactory WM. Seven benchmarks generalized to olfaction, whereas 2 failed to generalize. Evidence was insufficient to address the remaining 12 benchmarks (4 had mixed support and 8 were yet unaddressed). We conclude that the available evidence indicates that the sense of smell has a short-term memory system that mostly resembles WM processes in higher senses, although there are exceptions related to how olfactory WM performance is associated with other functions. We argue that researchers studying WM should explicitly consider evidence outside of the audio-visual senses when establishing theoretical frameworks. Further, we point out avenues for future research that may help close the remaining gaps in knowledge on this neglected topic.

Navigating the world and remembering events require processing information from various sensory modalities. However, research on human spatial memory and navigation is dominated by vision and little is known about the nonvisual senses. According to a recent theoretical framework, spatial memory and navigation evolved together with olfaction to aid navigation. We tasked participants with memorizing locations of odors and sounds in a virtual reality setting, hypothesizing that odor memory representations would disproportionately interfere with sound memory representations. In three recall times (immediate, 15-min delay, and 1-week delay), we tested whether spatial memory of odors would retroactively interfere with sounds. We predicted that performance should decline more in the sensory modality encoded first than in the modality encoded second, due to retroactive interference, especially when sounds are encoded first. Results indicated a decline in spatial memory performance over time, and similar retroactive interference effects from smells and sounds, but no olfactory-specific interference. However, exploratory results indicated that olfactory retroactive interference is apparent in error trials where participants tended to misplace sounds in the vicinity of smells related to the same concepts (e.g., misplacing the sound of a coffee maker at the location of the smell of coffee). There was no similar interference from sounds on odor misplacements, suggesting asymmetry or “olfactory dominance,” at the conceptual level. Our exploratory results suggest that the hypothesized unique role of olfactory retroactive interference might manifest in the type of errors, rather than in overall performance.

Chemosensory sensations are often hard to describe and quantify. Language models may facilitate a systematic understanding of sensory descriptions. We accessed consumer and expert reviews of wine, perfume, and food products (English language; about 68 million words in total) and analyzed their sensory descriptions. Using a novel data-driven method based on natural language data, we compared the three chemosensory vocabularies (wine, perfume, food) with respect to their vocabulary overlap and semantic properties, and explored their semantic spaces. The three vocabularies primarily differ with respect to domain specificity, concreteness, descriptor type preference and degree of gustatory vs. olfactory association. Wine vocabulary primarily distinguishes between white wine and red wine flavors and qualities. Food vocabulary separates drinkable and edible food products and ingredients, on the one hand, and savory and non-savory products, on the other. A salient distinction in all three vocabularies is between concrete and abstract/evaluative terms. Valence also plays a role in the semantic spaces of all three vocabularies, but valence is less prominent here than in general olfactory vocabulary. Our method allows a systematic comparison of sensory descriptors in the three product domains and provides a data-driven approach to derive sensory lexicons that can be applied by sensory scientists.

A persistent belief holds that humans can imagine visual content but not odors. While visual imagery is regarded as recreating a perceptual representation, it is unknown whether olfactory mental imagery shares a perceptual format. Visual imagery studies have demonstrated this perceptual formatting using distance and shape similarity judgments, whereas olfactory studies often use single-odor vividness ratings, complicating the establishment of perceptual formatting for odors. Using odor pair similarity scores from two experiments (odor-based: 8,880 ratings from 37 participants, including 20 women; label-based: 129,472 ratings from 2,023 participants, including 1,164 women), we observed a strong correlation (r =.71) between odor-based and label-based odor pairs. The correlation was unaffected by gender and age and was present in a wide range of self-perceived olfactory functions. Pleasantness similarity was the main determinant of overall similarity for both odor-based (r=−.63) and label-based (r=−.45) odor pairs. We then used a large language model to derive semantic similarity scores for the labels of all odor pairs. Semantic similarity only mediated a small part of the observed correlation, further supporting our conclusions that odor imagery shares a perceptual formatting with vision, that odor percepts may be elicited from verbal labels alone, and that odor pair pleasantness may be a dominant and accessible feature in this regard.

Rejection of food, including fruits and vegetables, is prevalent among children. In adolescents and adults, a link has been observed between food neophobia (the rejection of unfamiliar foods) and olfaction, which plays a key role in food acceptance. However, research on olfaction's role in food acceptance and rejection among children is limited. Utilizing the U-sniff test and the Italian Child Neophobia Scale, this study investigated associations between odor awareness, odor identification, food neophobia, and the acceptance of fruits and vegetables in Swedish children aged 9–12 years (n = 126). A Swedish version of the ChiPSO questionnaire on odor awareness (including subscales for food, social and environmental odors) was developed, and initial validation conducted through back translation, cognitive interviews, and exploratory factor analysis. Fruit and vegetable acceptance was assessed through a questionnaire and a tasting session. Findings indicated that food neophobia was associated with lower fruit and vegetable acceptance (questionnaire ρ = −0.296, p = 0.002; tasting session ρ = −0.273, p = 0.004) but no significant associations observed with odor awareness (ρ = 0.159, p = 0.094) or odor identification performance (ρ = −0.141, p = 0.176). However, odor awareness was negatively associated with vegetable acceptance (ρ = −0.200, p = 0.034), while odor identification performance showed no significant associations (questionnaire ρ = −0.049, p = 0.638; tasting session ρ = −0.101, p = 0.316). A negative association was found between odor identification performance and environmental odor awareness (ρ = −0.269, p = 0.010). This suggests that some children may struggle to identify odors due to emotional reactions and avoidant behaviors, reducing engagement and hindering identification. Further exploration of the relationship between olfaction and children's food acceptance or rejection is encouraged.

INTRODUCTION: Olfactory-based cognitive training may be of benefit to individuals at risk of dementia given the strong association between olfactory impairment and cognitive decline. The Mind Your Nose (MYN) trial compared an olfactory-based memory training protocol (OMT) to a visually-based memory training protocol (VMT) among older adults with subjective cognitive decline. METHODS: Participants (N = 53; 17 males; Mage= 72.77, standard deviation [SD] = 6.12) were randomly assigned in a 2:1 ratio to daily OMT (n = 36) or VMT (n = 17) intervention for 20 days. Outcomes were evaluated at baseline (T0), post-intervention (T1), and 1-month follow-up (T2) and included standardized measures of global olfaction (Sniffin’ Sticks) and cognition (National Institutes of Health Toolbox), as well as performance on the olfactory memory (OM) and the visual memory (VM) tasks, and measures of mood and meta-cognition. RESULTS: A significant interaction was found between treatment allocation, time, and modality of memory task at T1(β = −37.50, p = 0.008) and T2(β = −28.75, p = 0.041). Post-hoc comparisons revealed improvement in trained tasks; OMT led to improvement on the OM task (T1; g = 0.71, p = 0.036; T2; g = 0.72, p = 0.035), and VMT led to improvement on the VM task (T1; g = 1.22, p = 0.011; T2; g = 1.29, p = 0.006). Improvement on the untrained memory task only occurred in OMT (VM task, T1; g = 0.63, p = 0.071; T2; g = 0.74, p = 0.033). No interaction between treatment allocation and time was observed post intervention or at follow-up for global olfactory ability (T1; β = 0.27, p = 0.871; T2; β = −1.27, p = 0.296). DISCUSSION: Consistent with previous research, transfer gains from the OMT condition to an untrained VM task suggest that olfaction may contribute to a-modal representations of memory. We argue that memory-based olfactory training offers a new frontier for cognitive interventions among those at risk of dementia. Highlights: Relatively few cognitive training programs engage the olfactory sense. Olfactory memory training offers a new frontier of cognitive training for older adults. Olfaction may contribute to improved performance on trained and untrained tasks. The functional impact of olfactory training should be further explored.

Whereas human cognition develops through perceptually driven interactions with the environment, language models (LMs) are “disembodied learners” which might limit their usefulness as model systems. We evaluate the ability of LMs to recover sensory information from natural language, addressing a significant gap in cognitive science research literature. Our investigation is carried out through the sense of smell — olfaction — because it is severely underrepresented in natural language and thus poses a unique challenge for linguistic and cognitive modeling. By systematically evaluating the ability of three generations of LMs, including static word embedding models (Word2Vec, FastText), encoder-based models (BERT), and the decoder-based large LMs (LLMs; GPT-4o, Llama 3.1 among others), under nearly 200 training configurations, we investigate their proficiency in acquiring information to approximate human odor perception from textual data. As benchmarks for the performance of the LMs, we use three diverse experimental odor datasets including odor similarity ratings, imagined similarities of odor pairings from word labels, and odor-to-label ratings. The results reveal the possibility for LMs to accurately represent olfactory information, and describe the conditions under which this possibility is realized. Static, simpler models perform best in capturing odor-perceptual similarities under certain training configurations, while GPT-4o excels in simulating olfactory-semantic relationships, as suggested by its superior performance on datasets where the collected odor similarities are derived from word-based assessments. Our findings show that natural language encodes latent information regarding human olfactory information that is retrievable through text-based LMs to varying degrees. Our research shows promise for LMs to be useful tools in investigating the long debated relation between symbolic representations and perceptual experience in cognitive science.

Background: Subjective cognitive decline (SCD) is a risk factor for future cognitive impairment and dementia. It is uncertain whether the neurodegeneration of the cholinergic system is already present in SCD individuals. We aimed to review the current evidence about the association between SCD and biomarkers of degeneration in the cholinergic system.

Method: Original articles were extracted from three databases: Pubmed, Web of Sciences, and Scopus, in January 2023. Two researchers screened the studies independently.

Results: A total of 11 research articles were selected. SCD was mostly based on amnestic cognitive complaints. Cholinergic system biomarkers included neuroimaging markers of basal forebrain volume, functional connectivity, transcranial magnetic stimulation, or biofluid. The evidence showed associations between basal forebrain atrophy, poorer connectivity of the cholinergic system, and SCD

Conclusions: Degenerative changes in the cholinergic system can be present in SCD. Subjective complaints may help when identifying individuals with brain changes that are associated with cognitive impairment. These findings may have important implications in targeting individuals that may benefit from cholinergic-target treatments at very early stages of neurodegenerative diseases.

Background

More than a year after recovering from COVID-19, a large proportion of individuals, many of whom work in the healthcare sector, still report olfactory dysfunctions. However, olfactory dysfunction was common already before the COVID-19 pandemic, making it necessary to also consider the existing baseline prevalence of olfactory dysfunction. To establish the adjusted prevalence of COVID-19 related olfactory dysfunction, we assessed smell function in healthcare workers who had contracted COVID‐19 during the first wave of the pandemic using psychophysical testing.

Methods

Participants were continuously tested for SARS‐CoV‐2 IgG antibodies since the beginning of the pandemic. To assess the baseline rate of olfactory dysfunction in the population and to control for the possibility of skewed recruitment of individuals with prior olfactory dysfunction, consistent SARS-CoV‐2 IgG naïve individuals were tested as a control group.

Results

Fifteen months after contracting COVID‐19, 37% of healthcare workers demonstrated a quantitative reduction in their sense of smell, compared to only 20% of the individuals in the control group. Fifty-one percent of COVID‐19‐recovered individuals reported qualitative symptoms, compared to only 5% in the control group. In a follow-up study 2.6 years after COVID-19 diagnosis, 24% of all tested recovered individuals still experienced parosmia.

Conclusions

In summary, 65% of healthcare workers experienced parosmia/hyposmia 15 months after contracting COVID-19. When compared to a control group, the prevalence of olfactory dysfunction in the population increased by 41 percentage points. Parosmia symptoms were still lingering two-and-a half years later in 24% of SARS-CoV-2 infected individuals. Given the amount of time between infection and testing, it is possible that the olfactory problems may not be fully reversible in a plurality of individuals.

Introduction: Disgust sensitivity to body odors plays a role in a set of psychological mechanisms supposedly evolved to avoid pathogens. To assess individual differences in body odor disgust, we previously developed the body odor disgust scale (BODS) and validated it in English. The BODS presents six scenarios where disgust could be evoked by smells coming from an internal source and an external source. The present study aimed to validate the BODS in the Italian population and to find further evidence for its structural, construct, and criterion validity.

Methods: We used two large samples (N = 1,050, F = 527; and N = 402, F = 203, respectively) that were representative of the Italian population for sex and age.

Results: Across these two studies, we confirmed the hypothesized bifactor structure, with all the items loading onto a general body odor disgust sensitivity factor, and on two specific factors related to the internal structure. In terms of construct validity, we found that the BODS converged with pathogen disgust sensitivity of the three-domain disgust scale (TDDS) but was distinct from a general propensity to experience negative emotions. The BODS showed criterion validity in predicting the behavioral intentions toward COVID-19 avoidance behavior, although it did not seem to be incrementally valid when compared to the TDDS pathogen subscale. We also established scalar measurement invariance of the BODS regarding gender and found that women display higher levels of BODS.

Discussion: Results from the Italian version of the BODS indicate its structural, construct, nomological and criterion validity. Furthermore, our result on sex differences in disgust sensitivity are consistent with previous literature, and we discuss them in the broader context of cross-cultural and primate findings that points toward a possible evolutionary explanation of this difference.