# Neural representation of allegedly sex-specific human body odor compounds

Camille Ferdenzi, Arnaud Fournel, Luca Fantin, Stéphane Richard Ortegón, Cédric Manesse, Nicolas Baldovini, Marc Thévenet, Franck Lamberton, Danielle Ibarrola, Frédéric Faure, et al.

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Camille Ferdenzi, Arnaud Fournel, Luca Fantin, Stéphane Richard Ortegón, Cédric Manesse, et al. Neural representation of allegedly sex-specific human body odor compounds. NeuroImage, 2025, 310, pp.121114. 10.1016/j.neuroimage.2025.121114. hal-05361106

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# Neural representation of allegedly sex-specific human body odor compounds

Camille Ferdenzi<sup>a, *, b</sup>, Arnaud Fournel<sup>a</sup>, Luca Fantin<sup>a</sup>, Stéphane Richard Ortegón<sup>a</sup>, Cédric Manesse<sup>a</sup>, Nicolas Baldovini<sup>b</sup>, Marc Thévenet<sup>a</sup>, Franck Lamberton<sup>c, d</sup>, Danielle Ibarrola<sup>c, d, e</sup>, Frédéric Faure<sup>e, f</sup>, Moustafa Bensafi<sup>a</sup>

## ARTICLE INFO

### Keywords:

Human chemical communication

Body odor

Gender

Attractiveness

fMRI

## ABSTRACT

Body odors play an important role in nonverbal communication, and particularly in one's attractiveness. However, their central processing remains underexplored, especially as a function of gender. This study aims at identifying the neural networks involved in the processing of two allegedly sex-specific human body odor compounds (3-hydroxy-3-methylhexanoic acid, HMHA, and 3-methyl-3-sulfanylhexan-1-ol, MSH). We hypothesized that i) these body odors would be processed by different brain regions than non-body odors, and that ii) their role in attractiveness, if any, would be indicated by the activation of specific regions and by differential verbal and neurophysiological responses in men and women. Thirty participants (15 men, 15 women) performed a functional Magnetic Resonance Imaging (fMRI) session during which they rated the attractiveness of HMHA, MSH, and 5 non-body odorants. At the end of the session, participants rated all odors on multiple perceptual scales. HMHA activated visual (striate area and occipital gyrus) rather than olfactory brain regions. Men rated HMHA as more masculine than women did, and presented greater neural activity in the superior and medial frontal gyri while women activated the inferior frontal gyrus significantly more than men in response to this odor. MSH was processed as the other non-body odors, and not subject to gender differences. The results suggest that HMHA (not MSH) bears specific social information, resulting in a neural processing outside the main olfactory network. It is also processed differently in men and women, although our findings do not provide clear evidence in favor of relevance for one's attractiveness.

## 1. Introduction

In humans, there is increasing evidence that olfaction is involved in social interactions, especially in the form of non-verbal communication based on biological body odor produced by an emitter and perceived by a receiver (Loos et al., 2025; Ravreby et al., 2022; Roberts et al., 2020). Body odor is a complex mixture of organic volatile compounds that are produced by skin bacteria, through enzymatic transformation of molecules excreted by the body (mostly through sweat glands) (Leyden et al., 1981). Although biosynthetic pathways of most body odor compounds remain unknown, behavioral studies have highlighted the potential of

body odor to convey a wide range of information about individuals (Havlíček et al., 2017), serving the three main functions of olfaction: danger detection, ingestion, and social communication (Stevenson, 2010).

Indeed, in relation with the first function (danger detection), body odor carries cues regarding one's health status, which may contribute to avoidance behavior of sick individuals and to therefore prevent contamination (Olsson et al., 2014). With respect to the ingestion function, regulation of breast milk intake seems to be operated through olfactory stimulation of the newborns by secretions of specialized glands of the mothers' areola (Doucet et al., 2012). More substantial evidence is

<footnote><sup>a</sup> Université Claude Bernard Lyon 1, CNRS, INSERM, Centre de Recherche en Neurosciences de Lyon CRNL UMR5292, U1028, Bron, France</footnote>

<footnote><sup>b</sup> Institut de Chimie de Nice, CNRS UMR 7272, Université Côte d'Azur, Nice, France</footnote>

<footnote><sup>c</sup> Université Claude Bernard Lyon 1, CNRS, INSERM, SFR Lyon-Est UAR3453, US7, Lyon, France</footnote>

<footnote><sup>d</sup> CERMEP Imagerie du vivant, Bron, France</footnote>

<footnote><sup>e</sup> Hospices Civils de Lyon, Hôpital E. Herriot, Lyon, France</footnote>

<footnote><sup>f</sup> Infirmérie Protestante, Caluire, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: camille.ferdenzi@cnrs.fr (C. Ferdenzi).</footnote>
available on the influence of human chemical communication in social cognition. Body odors have been shown to convey information about individual characteristics, such as age (Gallagher et al., 2008; Haze et al., 2001), gender (Doty et al., 1982; Schleidt et al., 1981), or personality traits (Sorokowska et al., 2012). They are likely to be involved in emotional homeostasis and attachment (between parent and child, Schaal et al., 1980, Sullivan and Toubas, 1998; between romantic partners: Granqvist et al., 2019), as well as emotional contagion (de Groot and Smeets, 2017; Richard Ortegón et al., 2022). Mate choice is the most largely documented context for human chemical communication, with a series of perceptual studies that have revealed preferences for biological odors that provide cues to biological quality of a potential sexual partner (especially with regards to genetics and reproductive status). For example, preferences for body odors are modulated by the major histocompatibility complex MHC (emitter-receiver MHC-similarity, and – most reliably – emitter MHC-heterozygosity: Winternitz et al., 2017), a mechanism believed to have evolved because of its beneficial effects on offspring's fitness. Another adaptive phenomenon is men's preference for body odor samples collected during women's fertile phase of the menstrual cycle (Kuukasjarvi et al., 2004; Singh and Bronstad, 2001). Body odor is also perceived differently according to emitter's (and receiver's) sexual orientation (Lübke et al., 2012; Martins et al., 2005).

Regarding the neural underpinnings of body odor processing, it was found that body odors recruit a large network including the cingulate cortex, the occipital and angular gyri, but not (or less) the primary olfactory areas (Loos et al., 2025; Lundström et al., 2008). Different networks are recruited depending on the origin of the body odor. For instance, networks usually involved in the processing of fearful stimuli are activated by the body odor of a stranger contrasted with the odor of a friend (Lundström et al., 2008). Likewise, the body odor of a sister versus a friend activates a network associated with kin recognition (Lundström et al., 2009), and infants' odors activate the reward system of mothers who have just given birth (Lundström et al., 2013). More directly related to body odor attractiveness, exposure to sadness tears (Gelstein et al., 2011) and to body odors of sexually aroused donors (Zhou and Chen, 2008) modulate activations in the fusiform gyrus and hypothalamus, which are brain substrates of sexual arousal. But much of the current knowledge on brain substrates of body odor attractiveness is based on a given family of body odor compounds, historically believed to have a reproductive function in humans: the sexually dimorphic androgen steroids (produced in higher proportions by men). Among these, androstadienone has been found to activate a brain network related to social cognition and attention rather than olfaction only, even in the absence of conscious perception (Gulyás et al., 2004; Jacob et al., 2001). Differences were found in the hypothalamus as a function of perceiver's sex (Savic et al., 2001; but see Burke et al., 2012) and sexual orientation (Berglund et al., 2006; Savic et al., 2005), and interpreted as being the underpinnings of sex-differentiated behavioral responses. However, although androstadienone has been found to have psychological effects (on mood: Bensafi et al., 2004; Jacob and McClintock, 2000), sex-specificity in behavioral responses has been seriously questioned (Ferdenzi et al., 2016; Hummer and McClintock, 2009). Most importantly, the scientific justification for such a focus on androstenes – to the detriment of all the other components of human biological odor – is highly debatable in the quest for human sex pheromones specifically (Wyatt, 2015), but also more generally for the understanding of human body odor attractiveness.

Other body odor compounds than androstenes have thus attracted our attention in our quest to understand the role of odors in human attractiveness. These are 3-hydroxy-3-methylhexanoic acid (HMHA) and 3-methyl-3-sulfanylhexan-1-ol (MSH), which we were interested in because i) they are two major contributors to axillary odor (Hasegawa et al., 2004), and ii) they are present in sexually dimorphic amounts in men and women's body odor. Indeed, men and women were found to differ in the ratio of the precursors of HMHA and MSH secreted in the

armpit (Troccaz et al., 2009). Namely, in female samples, MSH precursor was found in larger quantities and HMHA precursor in smaller quantities on average than in male samples. Although interindividual variability was huge with significant overlap between men and women, the ratio HMHA precursor / MSH precursor was stable and 3 times higher in men than in women. Despite being very typical of human sweat odor, the effects of HMHA and MSH on human neuro-behavioral responses remain underexplored.

Only a few studies have investigated how these compounds are explicitly perceived. There is no consensus on the sex-related differences in sensitivity to HMHA and MSH. While some studies have found no difference between men and women (Ferdenzi et al., 2019, for HMHA; Troccaz et al., 2009, for HMHA and MSH) others have shown better performances in women in a detection task (Loos et al., 2017, for both compounds). Additionally, although these studies agree that HMHA is perceived as rather unpleasant and described with more negatively connoted terms (rancid, animalic, cheesy) than MSH (fruity, onion), sex differences are again inconclusive (no hedonic differences in Ferdenzi et al. (2019) versus lower pleasantness of HMHA for women in Ferdenzi et al. (2024)). Regarding the implicit processing of these odors, knowledge is also scarce. HMHA has only been investigated in one study which failed to show any pheromone-like effects using odor priming in a face perception task. As for MSH, there is to our knowledge no study assessing its implicit processing. In this study, we propose a combined psychological and neurophysiological approach in order to both investigate further how HMHA and MSH are perceived and identify the neural networks that are activated by both compounds. We hypothesized that, compared to odors of non-body origin, both HMHA and MSH would recruit non-olfactory areas, especially brain regions involved in social-attentional processes, such as the fusiform or cingulate gyri. Given the alleged sexual dimorphism of these compounds, we also hypothesized that gender differences could occur in the brain processing of these compounds. In particular, if HMHA and MSH have a role in inter-sexual attraction, areas related to sexual behavior, namely the hypothalamus (Burke et al., 2012; Savic et al., 2001) and fusiform gyrus (Gelstein et al., 2011; Zhou and Chen, 2008) should be recruited differently in men and women.

## 2. Materials and methods

### 2.1. Participants

Thirty participants (15 women, 15 men; all right-handed but one) aged 22.4±3.5 years old (Mean ± Standard Deviation) took part in the study. All participants reported being heterosexual, not regular smokers, non-pregnant (women) and having normal olfactory function, which was confirmed by psychometric measures (see method in Section 2.2. Olfactory Tests): average PEA threshold (11.9±3.0) was comparable to that of normosmic participants (11.9±2.9, N = 87; Croy et al., 2009), and ETOC scores (10.7±1.2 on average) were associated to more than 76 % chance of being normosmic (Joussain et al., 2016). Most participants (N = 25) were Caucasian, the others were African, Asian, Caucasian-African, and Caucasian-African-Asian. Men and women did not differ in age (W = 140, p = .257), time of testing during the day (W = 120.0, p = .770), hunger level on a 1–10 scale (W = 123.5, p = .659), general olfactory abilities (ETOC: W = 107.0, p = .828; PEA threshold: W = 113.0, p = 1.000). They also did not differ in relationship status (11 women out of 15 and 8 men out of 14 were in a relationship, one missing response; χ²(1) = .84, p = .359) but duration of the relationship tended to be longer in women (3.1±1.6 vs. 1.8±1.8 years; W = 22.0, p = .072). About half the women (N = 7) were taking hormonal contraception; among those who were not (N = 8), one was estimated as being in the fertile phase of her menstrual cycle (Ferdenzi et al., 2009). Participants provided written informed consent prior to participation. They were tested individually and received monetary compensation for their participation. The study was conducted in accordance with the
Declaration of Helsinki and the experimental procedure was approved by the local Lyon Sud-Est II review board (December 17, 2015).

## 2.2. Olfactory tests

Each participant took the 6-item short version (Joussain et al., 2016) of the European Test of Olfactory Capabilities ETOC (Thomas-Danguin et al., 2003). This test combines odor detection and identification of 6 odors: vanilla, orange, cinnamon, pine, cut grass and rose. Scores of detection (0–6) and identification (0–6) are summed to form an overall score (0–12). In addition, a finer measure of olfactory sensitivity was performed using a threshold test to phenyl ethyl alcohol (PEA) as described in Croy et al. (2009). This measure is based on a single-staircase, 3-alternative forced-choice procedure, using 16 dilutions of PEA (Hummel et al., 1997). Individual threshold is a score between 1 and 16 (16 representing the highest sensitivity). Both the ETOC and the PEA threshold were performed before the MRI session, except for 5 participants (3 men) who completed the ETOC afterwards.

## 2.3. Odorants

O odorants were delivered by an air-dilution olfactometer suited for fMRI (described in detail in Sezille et al., 2013). Seven odorants were used (odorant code, CAS and concentration): butyric acid (ABUT; 107-92-6; .01 %), cis-3-hexenol (CIS; 928-96-1; .24 %), 3-hydroxy-3-methylhexanoic acid (HMHA; 58888-76-9; 1 %), isoamyl acetate (ISO; 123-92-2; .32 %), D-limonene (LIM; 5989-27-5; pure), 3-methyl-3-sulfanylhexan-1-ol (MSH; 307964-23-4; 0.598g/L), (-)-Terpinen-4-ol (TER; 562-74-3; pure). Pure odorants (liquid) were provided by Sigma-Aldrich® except for HMHA and MSH, which were synthesized for the purpose of this study using procedures adapted from published protocols (see Supplementary methods), and dilutions were made using mineral oil (Sigma-Aldrich®). Odor concentrations were adjusted to reach iso-intensity, using HMHA concentration as a reference to allow for comparison with Ferdenzi et al. (2024). The odorants were selected because they belong to different categories: human body odors (male-specific HMHA: sweat/fermentation; female-specific MSH: sweat/on-ion), appetitive food odors (LIM: citrus, ISO: banana), and other non-human/non-food pleasant and unpleasant environmental odors (ABUT: vomit/fermented milk, unpleasant; CIS: cut grass, rather pleasant; TER: musty, rather unpleasant). ABUT, CIS, ISO, LIM, TER were chosen among odorants previously used in our research group and for which we already had information on their perceptual qualities. Odors were diffused at an airflow of 2 L/min. Two mL solution (odorous solution, or mineral oil alone for the AIR condition) was absorbed on a scentless polypropylene fabric (twice 1 × 6 cm; 3M®, Valley, NE, USA) placed in U-shaped Pyrex® tubes (VS technologies, France; volume: 10 ml; length: 50 mm; external diameter: 14 mm). The tubes were replaced every 2–3 consecutive participants.

## 2.4. Experimental procedure

An event-related design was used, comprising 8 conditions (non-odorized clean air and 7 odorants) repeated 16 times, with 20s inter-stimulus interval and 5s stimulus duration. Trials were distributed randomly in 4 fMRI scans (sessions). During each trial, the participants were instructed to breathe naturally, and odorants were released during expiration to ensure that they were present for the duration of the subsequent inhalation. Ten seconds after inhalation onset, participants were asked to rate the odor's attractiveness on a scale from 0 ("not at all attractive") to 4 ("very attractive"), with a 5-key response box (allocation of the fingers to one or the other direction of the scale was attributed randomly). Participants were asked to provide their response within a 5s time frame, and their response time (RT) was recorded.

The recorded signals during the fMRI sessions were respiratory flow, odor valve opening and time repetition (TR) signal from the fMRI

scanner, enabling event-related statistical analysis. Subject's respiratory signal was acquired using an airflow sensor (AWM720, Honeywell, France) connected to a nasal cannula (Cardinal Health, OH; 2.8 mm inner diameter) positioned in both nostrils. The sniffing signal was amplified and digitally recorded at 200 Hz using LabVIEW software®. Sniffs were preprocessed by removing the baseline and this signal was then down sampled into the fMRI frequency (1/RT) using the Fourier method implemented in the "resample" function from Scipy python library (https://www.scipy.org).

At the end of the fMRI sessions, the participants were asked to rate aloud each odor on the following perceptual scales ranging from 1 "not at all" to 9 "extremely": intensity, pleasantness, familiarity, edibility, trigeminal sensations of coolness, irritation, and pain, and "human" character of the odor. They then had to evaluate the odor on 9-point scales as if it belonged to a person by answering "to what extent is it the odor of someone:" (a) physically attractive, (b) feminine (1)/masculine (9), (c) socially dominant, and (d) physically dominant. The two latter dimensions were respectively defined as "is respected, influential, and often a leader" and "if this person got in a fistfight, this person would probably win" (from Puts et al., 2006). Finally, alongside these 12-dimension assessments, the participants had the possibility to give a free description of the odor.

The experiment lasted about 2 hours from participant's arrival to departure, including detailed explanation of the experiment, completion of the inclusion/demographic questionnaire, olfactory tests (olfactory abilities and thresholds), and imaging sessions.

## 2.5. fMRI data collection and processing

**Acquisition.** MRI images were acquired with a 3 Tesla MR-scanner (AWP66012 SIEMENS Prisma) at the CERMEP biomedical imaging platform (Lyon, France). The fMRI data were collected during four different sessions (285 vol/session, interleaved, AC/AP acquisition) with a 45 axial-slice 2D EPI sequence (matrix: 78 × 78; TR: 2,500 ms; TE: 30 ms; FA: 90; voxel size: 2.70 × 2.70 × 2.70 mm; FOV: 270). For each session, the first seven volumes were discarded to allow for T1 equilibration. A fieldmap was acquired before the fMRI sessions and used in the pre-processing step to reduce distortion in the sinus, orbitofrontal and temporal areas. A high-resolution T1-weighted brain image (3D MPR sequence – TR: 3500ms; TE: 3.86 ms; voxel size: 0.88 × 0.88 × 0.88 mm) was recorded and used in the EPI/T1 coregistration step.

**Preprocessing.** fMRI images were preprocessed using fMRIPrep (Esteban et al., 2019). fMRIPrep included standard steps: motion correction, co-registration between functional and structural images, normalization in stereotaxic space, estimation of regressors of no interest (see Supplementary methods for detailed preprocessing steps). After preprocessing, functional images were smoothed using a 5 × 5 × 5 mm FWHM Gaussian kernel to take account of between-subject anatomical variability.

## 2.6. Planned statistical analyses

**Odor ratings.** Statistical analyses of the behavioral data were conducted with R 4.0.2 (R Core Team, 2013). For each odor rating (attractiveness during the fMRI session, and the twelve perceptual ratings after the fMRI session), a 7 (odor) * 2 (gender) ANOVA was performed. For attractiveness ratings during the fMRI session, the mean value across all trials for each participant and each odor was used, to avoid missing values. The ANOVAs (type III sum of squares) were conducted using the afex package (Singmann et al., 2015) and post hoc comparisons (with Tukey's adjustment for multiple comparisons) were made with the emmeans package (Lenth et al., 2018). Additionally, FactoMineR (Lè et al., 2008) combined with factoextra (Kassambara and Mundt, 2017) package was used to perform a 3-dimensional Principal Component Analysis (PCA) on the perceptual ratings, so that the
proximity between odors can be visualized in all participants, and in men and women separately.

fMRI data. Statistical analyses were conducted using SPM12 (Statistical Parametric Mapping; Wellcome Department of Cognitive Neurology, London, UK) with Matlab (https://www.mathworks.com, version 9.4). The first-level statistical analysis was modeled using a canonical hemodynamic response function and eight regressors of interest were included corresponding to the eight conditions (control AIR, ABUT, CIS, LIM, HMHA, MSH, ISO, TER). The following signals were added to the model as nuisance regressors: 6 first aCompCor components (Behzadi et al., 2007), 6 motion parameters, frame displacements, nasal respiration (down sampled to fMRI frequency), a cosine basis set acting as a high-pass filter (with a 128s cutoff). First, the average of the 7 odor conditions was compared to the control AIR condition. Second, for each subject, seven contrasts were performed, consisting in comparing each odor condition (ABUT, CIS, LIM, HMHA, MSH, ISO, TER) with the “AIR” condition. For the second level, analyses were carried out using a standard random-effects model and group activation was assessed using a single-sample t-test. To identify significant activation cluster-extent

based thresholding was used with a primary threshold at *p* = 0.001 and a secondary statistical threshold of *p* < 0.05 corrected for multiple comparisons. All activation coordinates are reported in MNI space. Regions were identified using the atlas of human brain (Mai et al., 2004). Using the same method as for odor ratings, we conducted a PCA on the group brain activations elicited by each of the 7 odor conditions, to visualize how they position themselves in relation to each other in a multidimensional space. Third, men vs. women and women vs. men contrasts were performed to test for gender differences in brain responses to the body odor compounds (only the results for HMHA are reported, based on gender differences in the ratings found for this compound only).

## 3. Results

### 3.1. Attractiveness ratings (during the fMRI session)

Odor attractiveness ratings provided repeatedly by the participants while they were in the scanner (Fig. 1) did not differ between men and

<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Average ratings for the seven odors (Mean ± SD) sorted in descending order. Letters a, b, c, d and e identify significantly different groups according to post hoc pairwise comparisons (*p*<.05 after Sidak correction). ¹ Attractiveness, ² Femininity/Masculinity, ³ Social dominance, ⁴ Physical dominance of the individual.</figcaption></figure>
women (ANOVA, no main effect of gender: $F_{(1,24)} = 1.51, p = 0.232$; no gender × odor interaction: $F_{(4,7,111.8)} = 1.69, p = 0.147$; Fig 2.A). There was a main effect of odor ($F_{(4,7,111.8)} = 30.82, p < 0.0001$). Post hoc comparisons showed that this effect was due to the fact that ABUT (0.8 on a 0-to-4 scale) was less attractive than all the other odors, and that CIS (2.4), LIM (2.7) and ISO (3.0) - that were not statistically different from each other - were more attractive than all the other odors. MSH (1.4), TER (1.7) and HMHA (1.7) - not statistically different from each other - had intermediate scores that were significantly higher than those of ABUT but significantly lower than those of CIS, LIM and ISO (Table S1).

## 3.2. Perceptual ratings (after the fMRI sessions)

The average values of the perceptual ratings collected at the end of

the fMRI sessions are shown in Fig. 1 and detailed in Table S1. The intensity of the control condition (clean air) was lower on average (2.7 ± 1.5 on a 1-to-9 scale) than for all odorants, which varied in intensity between 4.5±2.0 for the weakest (HMHA) and 7.1 ± 1.4 for the strongest (ISO) on a 1-to-9 scale. MSH and ABUT were clearly unpleasant (mean pleasantness ratings of 2.8 and 2.4 respectively), HMHA and TER were slightly unpleasant (mean pleasantness of 4.5), and CIS, LIM and ISO had a positive valence (6.3, 6.7 and 7.1 respectively). Food odors (LIM, ISO) received the highest edibility ratings (5.9 for both, versus a range of 1.7 to 3.3 for the other non-food odors). The two body odor compounds HMHA and MSH received the highest ratings on the “human” scale (4.3 and 4.0 respectively, versus a range of 2.4 to 3.8 for the other non-body odors).

ANOVAs testing the effects of gender, odor, and gender by odor interaction revealed that, apart from a systematic main effect of odor

<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Perceptual ratings. (A) Attractiveness ratings of the 7 odorants during the fMRI scanning sessions in female (F) and male (M) participants (main effect of odor, *p* < 0.0001). (B) Representation of the 7 odors on the first two dimensions of the PCA for (B.i) male and (B.ii) female participants. (C) Masculinity ratings of the 7 odorants in female (F) and male (M) participants (significant gender × odor interaction, *p* = 0.012). These ratings are the responses to the question “to what extent is it the odor of someone: feminine (1)/masculine (9)”. Post hoc tests testing gender differences for each odor: \* *p* < 0.05. Black dots represent extreme values.</figcaption></figure>
(see Table 1), the only significant effect involving gender was a gender × odor interaction for the question “to what extent is it the odor of someone feminine (1)/masculine (9)” ($F_{(4,6,110.3)} = 3.19$, $p = 0.012$). Post hoc tests revealed that this interaction was solely due to a significant gender difference on HMHA, with men rating HMHA as more masculine ($5.5 \pm 2.2$) than women did ($4.2 \pm 2.4$, $p = 0.009$; Fig. 2C).

In the PCAs conducted on the perceptual ratings (Fig. S1), the first dimension, explaining a large part of the variance ($>67 \%$) can be interpreted as the valence, with positive valence on the right, which is closely linked with familiarity, attractiveness and edibility, and negative valence on the left, which is closely linked with pain, irritation, and odor masculinity. The second dimension ($10-14 \%$ of the variance) might represent edibility. The PCAs on the ratings of men (Fig. 2B.i) and of women (Fig. 2B.ii) showed similarities in the distribution of the odors in space, especially for MSH, LIM, ISO and ABUT but not for HMHA, further illustrating that this particular smell is perceived slightly differently by both genders.

### 3.3. Brain activations

**All odors vs. clean air contrast.** When contrasting all seven odors together versus the control condition (air), we found significant activations of olfactory areas, especially in the left and right amygdala, but also in the left and right orbitofrontal cortex, and the left superior frontal gyrus (Fig. 3, Table 2).

**Individual odors vs. clean air contrasts.** Each odor was then contrasted with the control condition (AIR). Detailed results are shown in Table 3. Regarding the two body odor compounds, HMHA only activated visual areas since significant clusters were mainly found in the striate area and other activations were found in the occipital gyrus (Fig. 4A), while MSH was associated with activations in a primary olfactory area, the right amygdala (Fig. 4B). The two unpleasant non-body odors showed the following significant activations. For ABUT, in clusters grouping amygdala/putamen/piriform cortex, in clusters that extend over insula, lateral orbital gyrus and frontal operculum, and in a cluster located in the striate area (ABUT; Fig. 4C). As for TER, activations were found in the right amygdala and the superior frontal gyrus (Fig. 4G). The pleasant non-body, non-food odor CIS activated the right amygdala (Fig. 4D). The two pleasant food odorants ISO and LIM were associated with activations in primary olfactory areas (amygdala/putamen/piriform cortex) and activations in insular area and in the left posterior orbital gyrus (Fig. 4E,F).

In the PCA performed on the brain activations by the 7 odors, it is

clear from the representation on the first two dimensions (explaining 62.3 % of the total variance; Fig. 5A) that HMHA has a distinct pattern from the other odors. ISO and LIM (the two pleasant food odors) are close to each other and at the opposite of HMHA on the second dimension. The first dimension seems to separate ABUT on the one hand, from CIS, TER and MSH on the other hand and the second dimension seems to separate HMHA from the other odors. Fig. 5B represents voxel correlation with the first (B.i) and the second (B.ii) component.

**Gender differences.** Because gender differences were found at the behavioral level (Fig. 2C: men rated HMHA as more masculine than women did), we examined how brain activity of men and women differed for this particular odor. Two clusters were found to be more activated in men in response to HMHA (Fig 6A). The first one (110 voxels; $p_{uncorr} = 0.021$) is in the superior frontal gyrus SFG ($FWE = 0.982$, $T = 4.54$, $x = -29$, $y = 35$, $z = 53$). The second one (193 voxels; $p_{uncorr} = 0.045$) is in the medial frontal gyrus MFG ($FWE = 1$, $T = 4.23$, $x = -42$, $y = 35$, $z = 41$). One cluster was more activated in women (23 voxels; $p_{uncorr} = 0.005$; Fig 6B) in the inferior frontal gyrus IFG (a first peak at $FWE = 0.970$, $T = 4.61$, $x = 44$, $y = 19$, $z = 11$; a second peak at $FWE = 0.999$, $T = 4.30$, $x = 47$, $y = 27$, $z = 14$). All clusters were found at $p < 0.001$ uncorrected.

For exploratory purposes (analyses not announced in Section 2.6.), we then examined the correlations between brain activations in these clusters, and the ratings of HMHA femininity/masculinity. While no significant correlations were found in women between activations in the inferior frontal gyrus and masculinity (Pearson's $R = -0.41$, $p = 0.124$), in men the activity in both clusters was significantly and positively correlated with masculinity (superior gyrus: $R = 0.61$, $p = 0.026$; medial frontal gyrus: $R = 0.60$, $p = 0.029$, Fig 6A). Interestingly, the correlation between brain activity and response time (RT) to the attractiveness ratings of HMHA was significant and negative in the medial frontal gyrus ($R = -0.84$, $p = 0.0003$), but not significant in the superior frontal gyrus ($R = -0.34$, $p = 0.249$) (Fig 6A). This means that men displaying higher activity in the medial frontal gyrus for the presentation of HMHA responded faster in the attractiveness rating task of this odor. However, they provided only marginally more negative ratings (correlation between activity in the medial frontal gyrus and attractiveness ratings: $R = -0.53$, $p = 0.063$).

### 4. Discussion

To this day, the central processing of body odors remains underexplored, and there is only little available knowledge on how gender-

<caption>**Table 1**</caption>

Results of the ANOVAs on the perceptual ratings (attractiveness ratings provided during the fMRI session, on a 0-to-4 scale; detailed ratings provided at the end of the fMRI session, on a 1-to-9 scale). Statistic F and p-value are indicated for the main effects of Gender and Odor, and for the Gender × Odor interaction. Means and standard deviations can be found in Supplementary Material (Table S1).

<table><thead><tr><th rowspan="2">Dimension</th><th colspan="2">Gender</th><th colspan="2">Odor</th><th colspan="2">Gender × Odor</th></tr><tr><th>Statistic</th><th>p-value</th><th>Statistic</th><th>p-value</th><th>Statistic</th><th>p-value</th></tr></thead><tbody><tr><td>Attractiveness fMRI</td><td>F<sub>(1,24)</sub> = 1.51</td><td>0.232</td><td>F<sub>(4,7,111.8)</sub> = 30.82</td><td>&lt;0.0001</td><td>F<sub>(4,7,111.8)</sub> = 1.69</td><td>0.147</td></tr><tr><td>Intensity</td><td>F<sub>(1,28)</sub> = 0.76</td><td>0.390</td><td>F<sub>(4,4,123.4)</sub> = 9.73</td><td>&lt;0.0001</td><td>F<sub>(4,4,123.4)</sub> = 2.31</td><td>0.056</td></tr><tr><td>Pleasantness</td><td>F<sub>(1,24)</sub> = 2.85</td><td>0.104</td><td>F<sub>(4,5,108.5)</sub> = 22.96</td><td>&lt;0.0001</td><td>F<sub>(4,5,108.5)</sub> = 0.83</td><td>0.519</td></tr><tr><td>Familiarity</td><td>F<sub>(1,24)</sub> = 0.52</td><td>0.476</td><td>F<sub>(4,3,104.4)</sub> = 15.84</td><td>&lt;0.0001</td><td>F<sub>(4,3,104.4)</sub> = 0.91</td><td>0.465</td></tr><tr><td>Edibility</td><td>F<sub>(1,24)</sub> = 0.17</td><td>0.688</td><td>F<sub>(3,9,94.7)</sub> = 19.20</td><td>&lt;0.0001</td><td>F<sub>(3,9,94.7)</sub> = 1.25</td><td>0.296</td></tr><tr><td>Freshness</td><td>F<sub>(1,24)</sub> = 0.22</td><td>0.646</td><td>F<sub>(4,5,107.7)</sub> = 12.07</td><td>&lt;0.0001</td><td>F<sub>(4,5,107.7)</sub> = 0.37</td><td>0.847</td></tr><tr><td>Irritation</td><td>F<sub>(1,24)</sub> = 2.19</td><td>0.152</td><td>F<sub>(4,5,109.2)</sub> = 7.97</td><td>&lt;0.0001</td><td>F<sub>(4,5,109.2)</sub> = 0.73</td><td>0.589</td></tr><tr><td>Pain</td><td>F<sub>(1,24)</sub> = 1.92</td><td>0.178</td><td>F<sub>(4,0,95.0)</sub> = 6.02</td><td>&lt;0.0001</td><td>F<sub>(4,0,95.0)</sub> = 0.75</td><td>0.562</td></tr><tr><td>Human</td><td>F<sub>(1,24)</sub> = 0.46</td><td>0.503</td><td>F<sub>(3,7,88.7)</sub> = 2.90</td><td>0.030</td><td>F<sub>(3,7,88.7)</sub> = 1.65</td><td>0.173</td></tr><tr><td>Attrac Indiv<sup>1</sup></td><td>F<sub>(1,24)</sub> = 1.12</td><td>0.300</td><td>F<sub>(4,7,112.9)</sub> = 11.94</td><td>&lt;0.0001</td><td>F<sub>(4,7,112.9)</sub> = 1.08</td><td>0.375</td></tr><tr><td>FemMasc Indiv<sup>2</sup></td><td>F<sub>(1,24)</sub> = 0.25</td><td>0.620</td><td>F<sub>(4,6,110.3)</sub> = 17.41</td><td>&lt;0.0001</td><td>F<sub>(4,6,110.3)</sub> = 3.19</td><td><strong>0.012</strong></td></tr><tr><td>SocDom Indiv<sup>3</sup></td><td>F<sub>(1,24)</sub> = 0.33</td><td>0.570</td><td>F<sub>(5,3,126.3)</sub> = 5.01</td><td>0.0002</td><td>F<sub>(5,3,126.3)</sub> = 0.50</td><td>0.787</td></tr><tr><td>PhyDom Indiv<sup>4</sup></td><td>F<sub>(1,24)</sub> = 0.02</td><td>0.884</td><td>F<sub>(4,0,97.0)</sub> = 2.99</td><td>0.022</td><td>F<sub>(4,0,97.0)</sub> = 0.36</td><td>0.837</td></tr></tbody></table>

<footnote n="1">¹ Attractiveness,</footnote>

<footnote n="2">² Femininity/Masculinity,</footnote>

<footnote n="3">³ Social dominance,</footnote>

<footnote n="4">⁴ Physical dominance of the individual.</footnote>
<figure><img src="image_4.png" /><figcaption>**Fig. 3.** Group activation maps for the contrast All odors > Air (all the 7 odors vs clean air). Color bar depicts the t-statistic. Higher activation was detected in the Amygdala, OrbitoFrontal Cortex and Superior Frontal Gyrus.</figcaption></figure>

<caption>**Table 2**</caption>

Activation following the stimulation with odorized air (all 7 odors are grouped in the analysis), in contrast with clean air. Results are presented with a cluster level family-wise error (FWE) probability, selected with a threshold of *p* < 0.05. Coordinates are reported in MNI space. OFC: Orbito-Frontal Cortex; SFG: Superior Frontal Gyrus

<table><thead><tr><th>Cluster</th><th>Region</th><th>Cluster size</th><th>Cluster FWE</th><th>Peak FWE</th><th>Peak T</th><th>x</th><th>y</th><th>z</th></tr></thead><tbody><tr><td rowspan="3">1</td><td rowspan="3">Amygdala (L)</td><td rowspan="3">110</td><td rowspan="3">0.000</td><td><strong>0.001</strong></td><td>7.53</td><td>-15</td><td>-5</td><td>-13</td></tr><tr><td><strong>0.035</strong></td><td>6.29</td><td>-21</td><td>-3</td><td>-19</td></tr><tr><td>0.220</td><td>5.61</td><td>-26</td><td>-11</td><td>-10</td></tr><tr><td rowspan="3">2</td><td rowspan="3">Amygdala (R), bordering hippocampus (R)</td><td rowspan="3">193</td><td rowspan="3">0.000</td><td><strong>0.003</strong></td><td>7.26</td><td>25</td><td>0</td><td>-19</td></tr><tr><td>0.056</td><td>6.12</td><td>14</td><td>-8</td><td>-16</td></tr><tr><td>0.082</td><td>5.98</td><td>22</td><td>-11</td><td>-13</td></tr><tr><td rowspan="3">3</td><td rowspan="3">OFC inferior part (L), bordering insula (L)</td><td rowspan="3">158</td><td rowspan="3">0.000</td><td>0.093</td><td>5.93</td><td>-45</td><td>19</td><td>-4</td></tr><tr><td>0.137</td><td>5.79</td><td>-26</td><td>35</td><td>-13</td></tr><tr><td>0.342</td><td>5.45</td><td>-39</td><td>3</td><td>-10</td></tr><tr><td rowspan="2">4</td><td rowspan="2">OFC inferior part (R), bordering insula (R) and planum polare</td><td rowspan="2">32</td><td rowspan="2">0.044</td><td>0.992</td><td>4.45</td><td>49</td><td>16</td><td>-7</td></tr><tr><td>1.000</td><td>3.94</td><td>44</td><td>30</td><td>-4</td></tr><tr><td rowspan="2">5</td><td rowspan="2">SFG (L)</td><td rowspan="2">33</td><td rowspan="2">0.039</td><td>0.998</td><td>4.31</td><td>-4</td><td>19</td><td>50</td></tr><tr><td>1.000</td><td>4.22</td><td>-2</td><td>27</td><td>35</td></tr></tbody></table>

typical body odors are processed. While previous studies had mainly focused on androgen steroids, we proposed in the present work to investigate the neural underpinnings of HMHA and MSH perception, in both men and women. As these compounds are known to be produced in sexually dimorphic proportions, we supposed that HMHA and MSH could be involved in male-female attractiveness. They were consequently expected to activate different brain substrates than non-body odors, possibly brain regions involved in sexual behaviors, and to elicit gender-specific processing both at the verbal (ratings) and neurophysiological levels.

From a behavioral perspective, we observed that HMHA was processed in a distinct manner compared to the other (mostly non-body) odors we used. This was particularly visible on the PCAs performed on psychological ratings. Further differences were observed at the neurophysiological level for HMHA, which also presented unique patterns of brain activity among all odor conditions. Indeed, our fMRI data show that HMHA increased activity in visual regions (the left striate area and left occipital gyrus), but did not involve the olfactory network. While these findings seem surprising, they do corroborate previous studies reporting an absence of activity within primary and secondary olfactory areas during the presentation of body odors (Lundström et al., 2009, 2008) or male endogenous compounds (Savic et al., 2001). Among the possible explanations proposed by Lundström and Olsson (2010), one

states that the signaling value of odors may define, at very early stages of odor perception, the neural pathways through which they will be processed, similarly to what has been observed in non-human animals. If so, body odors (and in this case HMHA) could possess specific signaling value which may be crucial for nonverbal communication, explaining its processing in distinct brain areas, regardless of their perceptual characteristics as measured with explicit ratings. In fact, it has been argued that attractiveness specifically is a form of chemical nonverbal communication which is crossmodal by nature (Groyecka et al., 2017). In ecological situations, perception of a body odor is usually paired with at least visual cues which also play a part in mate choice (Saxton et al., 2009). In our study, unimodal stimulation using HMHA, may have re-activated visuo-olfactory crossmodal correspondences by top-down processes such as the anticipation of the visual perception of a human being. The role of these top-down processes could be to seek for complementary sensory information which could help in selecting potential mates (Trebický et al., 2023).

On the other hand, perception of MSH was only related to increased activity in the right amygdala and amygdaloid area, a pattern which does not replicate what was observed in the case of HMHA. This result could mean that the olfactory stimulation using MSH in our study did not hold a signaling value of “body odor” as salient as that of HMHA. Why that is the case cannot be asserted with certainty, but we suppose it
<caption>**Table 3**</caption>

Activation following the stimulation with each of the 7 odors separately in contrast with clean air. Results are presented with a cluster level family-wise error (FWE) probability, selected with a threshold of *p* < 0.05. Coordinates are reported in MNI space. unc.: uncorrected. OFC: Orbito-Frontal Cortex; SFG: Superior Frontal Gyrus.

<table><thead><tr><th>Cluster</th><th>Region</th><th>Cluster size</th><th>Cluster FWE</th><th>Peak unc.p</th><th>Peak FWE</th><th>Peak T</th><th>x</th><th>y</th><th>z</th></tr></thead><tbody><tr><td colspan="10"><strong>HMHA</strong></td></tr><tr><td>1</td><td>Striate area (L)</td><td>44</td><td>0.009</td><td>0.000</td><td>0.557</td><td>5.27</td><td>-2</td><td>-84</td><td>2</td></tr><tr><td>2</td><td>Occipital gyrus (L)</td><td>35</td><td>0.028</td><td>0.000<br>0.000</td><td>0.977<br>1.000</td><td>4.57<br>3.93</td><td>-15<br>-10</td><td>-105<br>-100</td><td>-1<br>-7</td></tr><tr><td colspan="10"><strong>MSH</strong></td></tr><tr><td>1</td><td>Amygdala (R) and amygdaloid area</td><td>39</td><td>0.017</td><td>0.000<br>0.000</td><td>0.125<br>0.996</td><td>5.82<br>4.37</td><td>28<br>17</td><td>0<br>-3</td><td>-19<br>-16</td></tr><tr><td colspan="10"><strong>ABUT</strong></td></tr><tr><td>1</td><td>Amygdala (L), bordering putamen, insular gyrus, temporal piriform and thalamus</td><td>105</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td><strong>0.002</strong><br>0.967<br>0.978</td><td>7.40<br>4.61<br>4.55</td><td>-21<br>-29<br>-34</td><td>-3<br>-11<br>-19</td><td>-16<br>-10<br>-7</td></tr><tr><td>2</td><td>Temporal and frontal piriform cortex (R), Amygdala (R)</td><td>165</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td><strong>0.039</strong><br>0.084<br>0.190</td><td>6.25<br>5.97<br>5.67</td><td>25<br>20<br>25</td><td>5<br>3<br>-11</td><td>-19<br>-10<br>-13</td></tr><tr><td>3</td><td>Frontal operculum (L), bordering OFC inferior part and insula</td><td>78</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.393<br>0.691<br>1.000</td><td>5.40<br>5.11<br>4.15</td><td>-50<br>-31<br>-26</td><td>19<br>19<br>21</td><td>-4<br>-16<br>-7</td></tr><tr><td>4</td><td>Striate area (R,L)</td><td>140</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.984<br>0.986<br>0.998</td><td>4.52<br>4.50<br>4.31</td><td>-10<br>12<br>12</td><td>-78<br>-86<br>-78</td><td>11<br>8<br>11</td></tr><tr><td>5</td><td>Frontal operculum (R), bordering OFC inferior part and insula</td><td>34</td><td>0.036</td><td>0.000<br>0.000</td><td>0.990<br>1.000</td><td>4.46<br>3.88</td><td>49<br>47</td><td>19<br>30</td><td>-7<br>-4</td></tr><tr><td colspan="10"><strong>CIS</strong></td></tr><tr><td>1</td><td>Amygdala (R), bordering piriform and hippocampus</td><td>45</td><td>0.008</td><td>0.000<br>0.000</td><td>0.294<br>0.987</td><td>5.50<br>4.50</td><td>25<br>20</td><td>3<br>-3</td><td>-19<br>-16</td></tr><tr><td colspan="10"><strong>ISO</strong></td></tr><tr><td>1</td><td>Amygdala (L), bordering olfactory tubercle and putamen</td><td>82</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td><strong>0.001</strong><br>0.158<br>0.999</td><td>7.70<br>5.73<br>4.28</td><td>-26<br>-15<br>-15</td><td>0<br>-5<br>11</td><td>-16<br>-13<br>-1</td></tr><tr><td>2</td><td>Amygdala (R), bordering piriform</td><td>143</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td><strong>0.044</strong><br>0.142<br>0.222</td><td>6.21<br>5.77<br>5.61</td><td>28<br>22<br>22</td><td>5<br>-3<br>-11</td><td>-19<br>-16<br>-13</td></tr><tr><td>3</td><td>Insula (L), bordering piriform, frontal operculum and orbital gyrus</td><td>100</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.257<br>0.831<br>0.946</td><td>5.55<br>4.91<br>4.68</td><td>-39<br>-26<br>-45</td><td>8<br>35<br>19</td><td>-10<br>-13<br>-7</td></tr><tr><td colspan="10"><strong>LIM</strong></td></tr><tr><td>1</td><td>Amygdala (L), bordering putamen, piriform and hypothalamus</td><td>136</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td><strong>0.034</strong><br>0.054<br>0.880</td><td>6.30<br>6.13<br>4.84</td><td>-15<br>-26<br>-15</td><td>-5<br>-11<br>11</td><td>-13<br>-10<br>2</td></tr><tr><td>2</td><td>Amygdala (R), bordering insula</td><td>124</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.116<br>0.365<br>1.000</td><td>5.85<br>5.43<br>3.86</td><td>25<br>39<br>12</td><td>0<br>8<br>-8</td><td>-16<br>-10<br>-16</td></tr><tr><td>3</td><td>Insula (L), bordering frontal operculum, planum polare and piriform</td><td>75</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.172<br>0.285<br>0.946</td><td>5.70<br>5.52<br>4.69</td><td>-45<br>-39<br>-39</td><td>16<br>3<br>13</td><td>-4<br>-10<br>-10</td></tr><tr><td>4</td><td>Posterior orbital gyrus (L)</td><td>35</td><td>0.030</td><td>0.000</td><td>0.551</td><td>5.27</td><td>-29</td><td>32</td><td>-13</td></tr><tr><td colspan="10"><strong>TER</strong></td></tr><tr><td>1</td><td>Amygdala (R)</td><td>62</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.222<br>0.977<br>1.000</td><td>5.61<br>4.57<br>3.89</td><td>25<br>17<br>22</td><td>0<br>0<br>-11</td><td>-19<br>-16<br>-10</td></tr><tr><td>2</td><td>SGF (R,L)</td><td>51</td><td>0.000</td><td>0.000<br>0.000<br>0.000</td><td>0.912<br>0.993<br>1.000</td><td>4.78<br>4.44<br>3.77</td><td>-4<br>1<br>1</td><td>19<br>16<br>11</td><td>50<br>44<br>59</td></tr></tbody></table>
<figure><img src="image_5.png" /><figcaption>**Fig. 4.** Brain activations elicited by each of the 7 odors contrasted with clean air: (A) HMHA (B) MSH (C) ABUT (D) CIS (E) ISO (F) LIM and (G) TER. While MSH, ABUT, TER, CIS, LIM, ISO elicited activation mainly in olfactory areas, main brain activation for HMHA was found in Striate area and Occipital gyrus. In all panels, the color bar depicts the t-statistic.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Fig. 5.** (A) Principal Component Analysis on the brain activations elicited by each of the 7 odors. (B.i) and (B.ii) indicate voxels correlation with the first and second PCA component respectively. The color bar indicates correlation R values.</figcaption></figure>

may be explained by some of our methodological choices. For instance, we reproduced an approach consisting in the presentation of individual synthetic body odor components. While this method has been used several times (Berglund et al., 2006; Savic et al., 2005, 2001) and is easily replicable, it does not account for the complexity of natural body odors (i.e. sampled on human donors). MSH alone may thus be not representative enough of human body odors to possess a distinct signaling value from non-body odors (contrary to HMHA), explaining why it only involved the amygdala. Furthermore, because we controlled all odor conditions to be approximately iso-intense, the body odors were presented above the detection threshold for all participants, which likely corresponds to higher concentrations than what is perceived in daily

interactions. These choices may have affected the processing of MSH in olfactory and visual areas (more so than that of HMHA for unknown reasons), but also the processing of both HMHA and MSH in a social-attention network. Indeed, we initially expected that perception of HMHA and MSH would induce activity in such a network comprised of the fusiform gyrus and cingulate gyrus, documented as being involved in the processing of putative chemosignals broadly speaking (Gelstein et al., 2011; Lundström et al., 2008; Savic and Berglund, 2010). Our results did not confirm this hypothesis, which may be attributed to the limited ecological accuracy of our body odor conditions. Considering this we suggest that future studies on the neural processing of body odors should consider using a methodology as close as possible to
<figure><img src="image_7.png" /><figcaption>**Fig. 6.** Gender differences in brain activations elicited by the odor of HMHA presented at *p* < 0.001 uncorrected. (A) Contrast men vs. women showing differences in the superior (green) and the medial (red) frontal gyrus, and correlation graphs between the level of brain activation in both clusters and femininity/masculinity ratings (on the left) as well as time to provide attractiveness judgments in the fMRI (on the right). (B) Contrast women vs. men showing differences in the inferior frontal gyrus. The color bar indicates t-statistics.</figcaption></figure>

real-life interactions.

Regarding the existence of a gender-specific processing of body odors, despite limited generalizability due to small sample size, we validated this hypothesis only for HMHA. At the explicit (verbal) level, men rated HMHA as more masculine than women. In response to this result, we further investigated the effect of HMHA in order to determine whether this odor elicited gender-specific neural responses. Interestingly, men showed increased activity in the superior and medial frontal gyri (SFG and MFG respectively), which are known to be mainly involved in cognitive load and attention to sensory inputs (Mayer et al., 2016; Regenbogen et al., 2013). One may thus assume that men allocate more cognitive resources than women when processing HMHA for attractiveness judgements. Perhaps these brain responses reflect the fact that in heterosexual men, attractiveness judgements of male body odors generate a discrepancy (i.e., a mismatch between the gender typicality of the odor and their sexual orientation), increasing the resources necessary for a response. The negative correlation we found between MFG activity and response time on attractiveness ratings in men, could also suggest that the more men allocate cognitive resources, the better they are able to create a clear mental representation of this odor. Nevertheless, these inferences on cognitive load have not been directly measured and are only interpreted in the light of neurophysiological data. To verify these hypotheses, specific tools such as the NASA Task Load Index (Hart and Staveland, 1988) could be used as a psychometrical assessment of cognitive load.

In women, HMHA induced greater activity in the inferior frontal gyrus (IFG), which has been related to higher social openness in women in other study (Lübke et al., 2014). According to the authors, this result could represent higher importance attributed individually to body odors as social signals. We could therefore assume that in our study, women attributed more social relevance to HMHA than men did. This is likely for two reasons, the first being the overall higher sensitivity to body odors in women (Havlicek et al., 2008), and the second being the masculine typicality of HMHA which may be contextually more important to heterosexual women for attractiveness judgements – although this is not observable in the explicit odor ratings. The IFG has also been discussed as involved in several social behaviors, for instance emotional empathy (Shamay-Tsoory et al., 2009) and behavioral

mirroring (Kilner et al., 2009). In view of these various elements of the literature, it remains difficult to draw reliable conclusions about the cognitive processes in play in women when they form their judgments of attractiveness of HMHA.

Previous reports of neuroimaging when using gender-typical body odor compounds have attracted great attention towards the hypothalamus. Indeed, increased activity in this region has been observed during the presentation of androgen steroids to heterosexual women (Savic et al., 2001) and homosexual men (Savic et al., 2005). Conversely, heterosexual men and homosexual women activated the hypothalamus when presented with oestratetraenol (Berglund et al., 2006; Savic et al., 2001). In our study, although we report gender-specific responses during the perception of HMHA, they did not concern the hypothalamus. This finding, as well as the fact that men and women did not differ in their attractiveness ratings of HMHA, are in line with a recent work using odor priming (Ferdenzi et al., 2024) that failed to show an effect of HMHA on intrasexual competition or intersexual attraction.

Finally, it must be considered that some characteristics of our participants may have induced variability in our data, namely phase of the menstrual cycle and relationship status. These factors which have been discussed as influencing the perception of body odors (e.g., Havlicek et al., 2005), were not controlled for in our study. The hormonal influences of odor processing in women by most accounts affect sensitivity to various types of olfactory cues (Derntl et al., 2013; Nováková et al., 2014). Yet, these affirmations are currently debated due to difficult reproducibility, mainly because of a lack of standardized definition and calculation of the natural menstrual cycle (Schmalenberger, 2021). It cannot be excluded that the outcomes of this study would have been different if women were all tested during the fertile phase of their cycle (providing reliable estimation of fertility was used, such as hormonal assessment). However, controlling this unfortunately would have presented too much of a logistic challenge when it came to planning the MRI sessions. Regarding relationship status, it is possible that during attractiveness judgements, individuals who are already in a relationship may subconsciously reduce the social attention allocated towards the processing of body odors. Since this could be applied to both mate selection and intrasexual competition, this factor should be taken into account when possible.
## 5. Conclusion

The present work provided a first approach of gender-specific processing, at the perceptual and neurophysiological levels, of HMHA and MSH, two body odor compounds allegedly produced in sexually dimorphic proportions. While MSH was processed just like the other non-body odors, we found that HMHA was processed differently, notably because it involved visual rather than olfactory brain regions. It has also been shown that HMHA may provide some information about gender typicality at least in men. Gender differences in brain activations elicited by HMHA suggest i) a greater cognitive load in men when asked to rate attractiveness of an odor that is a mismatch with their sexual orientation (greater activation of the SFG and MFG, activation positively correlated with masculinity ratings and negatively correlated with attractiveness response time) and ii) social relevance of this smell in women (greater activation of the IFG). However, the results of this study brings no compelling perceptual or neurophysiological evidence that HMHA, and a fortiori MSH, may have a particular relevance in human attractiveness. Future studies should nonetheless prioritize ecological accuracy of body odor conditions, and perhaps consider pairing olfactory with visual inputs, given the cross-modality of attractiveness judgements.

## Funding

This work was supported by the Agence Nationale de la Recherche (grant number PDOC program, ATTRASENS project, to CF).

## Statements relating to ethics and integrity

Participants provided written informed consent prior to participation. The study was conducted in accordance with the Declaration of Helsinki and the experimental procedure was approved by the local Lyon Sud-Est II review board (December 17, 2015).

## CRediT authorship contribution statement

**Camille Ferdenzi:** Writing – review & editing, Writing – original draft, Validation, Supervision, Project administration, Methodology, Investigation, Funding acquisition, Data curation, Conceptualization.
**Arnaud Fournel:** Writing – review & editing, Visualization, Software, Methodology, Investigation, Formal analysis, Conceptualization.
**Luca Fantin:** Writing – review & editing.
**Stéphane Richard Ortegón:** Writing – review & editing, Formal analysis.
**Cédric Manesse:** Writing – review & editing, Investigation.
**Nicolas Baldovini:** Writing – review & editing, Methodology.
**Marc Thévenet:** Writing – review & editing, Methodology.
**Franck Lamberton:** Writing – review & editing, Methodology, Investigation.
**Danielle Ibarrola:** Writing – review & editing, Methodology, Investigation.
**Frédéric Faure:** Writing – review & editing, Investigation.
**Moustafa Bensafi:** Writing – review & editing, Supervision, Methodology, Conceptualization.

## Declaration of competing interest

The authors declare no conflict of interest.

## Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.neuroimage.2025.121114.

## Data availability

Data will be made available on request.

## References

Behzadi, Y., Restom, K., Liau, J., Liu, T.T., 2007. A component based noise correction method (CompCor) for BOLD and perfusion based fMRI. Neuroimage 37, 90–101. https://doi.org/10.1016/j.neuroimage.2007.04.042.

Bensafi, M., Tsutsui, T., Khan, R., Levenson, R.W., Sobel, N., 2004. Sniffing a human sex-steroid derived compound affects mood and autonomic arousal in a dose-dependent manner. Psychoneuroendocrinology 29, 1290–1299. https://doi.org/10.1016/ s0306-4530(04)00046-0.

Berglund, H., Lindstrom, P., Savic, I., 2006. Brain response to putative pheromones in lesbian women. Proc. Natl. Acad. Sci. U. S. A. 103, 8269–8274. https://doi.org/ 10.1073/pnas.0600331103.

Burke, S.M., Veltman, D.J., Gerber, J., Hummel, T., Bakker, J., 2012. Heterosexual men and women both show a hypothalamic response to the chemo-signal androstadienone. PLoS One 7, e40993. https://doi.org/10.1371/journal. pone.0040993.

Croy, I., Lange, K., Krone, F., Negoias, S., Seo, H.-S., Hummel, T., 2009. Comparison between odor thresholds for phenyl ethyl alcohol and butanol. Chem. Senses 34, 523–527. https://doi.org/10.1093/chemse/bjp029.

de Groot, J.H.B., Smeets, M.A.M., 2017. Human fear chemosignaling: evidence from a meta-analysis. Chem. Senses 42, 663–673. https://doi.org/10.1093/chemse/bjp049.

Dernl, B., Schoepf, V., Kollndorfer, K., Lanzenberger, R., 2013. Menstrual cycle phase and duration of oral contraception intake affect olfactory perception. Chem. Senses 38, 67–75. https://doi.org/10.1093/chemse/bjs084.

Doty, R.L., Green, P.A., Ram, C., Yankell, S.L., 1982. Communication of gender from human breath odors: relationship to perceived intensity and pleasantness. Horm. Behav. 16, 13–22. https://doi.org/10.1016/0018-506X(82)90002-2.

Doucet, S., Soussignan, R., Sagot, P., Schaal, B., 2012. An overlooked aspect of the human breast: areolar glands in relation with breastfeeding pattern, neonatal weight gain, and the dynamics of lactation. Early Hum. Dev. 88, 119–128. https://doi.org/ 10.1016/j.earlhumdev.2011.07.020.

Esteban, O., Markiewicz, C.J., Blair, R.W., Moodie, C.A., Isik, A.I., Erramuzpe, A., Kent, J. D., Goncalves, M., DuPre, E., Snyder, M., Oya, H., Ghosh, S.S., Wright, J., Durnez, J., Poldrack, R.A., Gorgolewski, K.J., 2019. fMRIPrep: a robust preprocessing pipeline for functional MRI. Nat. Methods 16, 111–116. https://doi.org/10.1038/s41592- 018-0235-4.

Ferdenzi, C., Delplanque, S., Atanassova, R., Sander, D., 2016. Androstadienone's influence on the perception of facial and vocal attractiveness is not sex specific. Psychoneuroendocrinology. 66, 166–175. https://doi.org/10.1016/j. psyneuen.2016.01.016.

Ferdenzi, C., Fournel, A., Baldovini, N., Poupon, D., Ligout, D., Thévenet, M., Bouet, R., Bensafi, M., 2024. Influence of the human body odor compound HMHA on face perception. Perception. https://doi.org/10.1177/03010066231222473.

Ferdenzi, C., Razafindrazaka, H., Baldovini, N., Poupon, D., Pierron, D., Bensafi, M., 2019. Influence of gender and culture on the perception of acidic compounds of human body odor. Physiol. Behav. 210, 112561. https://doi.org/10.1016/j. physbeh.2019.112561.

Ferdenzi, C., Schaal, B., Roberts, S.C., 2009. Human axillary odor: are there side-related perceptual differences? Chem. Senses 34, 565–571. https://doi.org/10.1093/ chemse/bjp037.

Gallagher, M., Wysocki, C.J., Leyden, J.J., Spielman, A.I., Sun, X., Preti, G., 2008. Analyses of volatile organic compounds from human skin. Br. J. Dermatol 159, 780–791. https://doi.org/10.1111/j.1365-2133.2008.08748.x.

Gelstein, S., Yeshurun, Y., Rozenkrantz, L., Shushan, S., Frumin, I., Roth, Y., Sobel, N., 2011. Human tears contain a chemosignal. Science 331, 226–230. https://doi.org/ 10.1126/science.1198331.

Granqvist, P., Vestbrant, K., Döllinger, L., Liuzza, M.T., Olsson, M.J., Blomkvist, A., Lundström, J.N., 2019. The scent of security: odor of romantic partner alters subjective discomfort and autonomic stress responses in an adult attachment-dependent manner. Physiol. Behav. 198, 144–150. https://doi.org/10.1016/j. physbeh.2018.08.024.

Groyecka, A., Pisanski, K., Sorokowska, A., Havlíček, J., Karwowski, M., Puts, D., Roberts, S.C., Sorokowski, P., 2017. Attractiveness is multimodal: beauty is also in the nose and ear of the beholder. Front. Psychol. 8. https://doi.org/10.3389/ fpsyg.2017.00778.

Gulyás, B., Kéri, S., O'Sullivan, B.T., Decety, J., Roland, P.E., 2004. The putative pheromone androstadienone activates cortical fields in the human brain related to social cognition. Neurochem. Int. 44, 595–600. https://doi.org/10.1016/j. neuint.2003.10.003.

Hart, S.G., Staveland, L.E., 1988. Development of NASA-TLX (Task Load Index): results of empirical and theoretical research. Advances in Psychology. Elsevier, pp. 139–183. https://doi.org/10.1016/S0166-4115(08)62386-9.

Hasegawa, Y., Yabuki, M., Matsukane, M., 2004. Identification of new odoriferous compounds in human axillary sweat. Chem. Biodivers. 1, 2042–2050. https://doi. org/10.1002/cbdv.200490157.

Havlíček, J., Fialová, J., Roberts, S.C., 2017. Individual variation in body odor. In: Buettner, A. (Ed.), Springer Handbook of Odor. Springer Handbooks. Springer International Publishing, Cham, pp. 125–126. https://doi.org/10.1007/978-3-319- 26932-0_50.

Havlíček, J., Roberts, S.C., Flegr, J., 2005. Women's preference for dominant male odour: effects of menstrual cycle and relationship status. Biol. Lett. 1, 256–259. https://doi. org/10.1098/rsbl.2005.0332.

Havlíček, J., Saxton, T.K., Roberts, S.C., Jozifkova, E., Lhota, S., Valentova, J., Flegr, J., 2008. He sees, she smells? Male and female reports of sensory reliance in mate choice and non-mate choice contexts. Pers. Individ. Dif. 45, 565–570. https://doi. org/10.1016/j.paid.2008.06.019.
Haze, S., Gozu, Y., Nakamura, S., Kohno, Y., Sawano, K., Ohta, H., Yamazaki, K., 2001. 2-Nonenal newly found in human body odor tends to increase with aging. J. Invest. Dermatol. 116, 520-524. https://doi.org/10.1046/j.0022-202x.2001.01287.x.

Hummel, T., Sekinger, B., Wolf, S.R., Pauli, E., Kobal, G., 1997. Sniffin' sticks": olfactory performance assessed by the combined testing of odor identification, odor discrimination and olfactory threshold. Chem. Senses 22, 39-52. https://doi.org/10.1093/chemse/22.1.39.

Hummer, T.A., McClintock, M.K., 2009. Putative human pheromone androstadienone attunes the mind specifically to emotional information. Horm. Behav. 19, 548-559. https://doi.org/10.1016/j.yhbeh.2009.01.002.

Jacob, S., Kinnunen, L.H., Metz, J., Cooper, M., McClintock, M.K., 2001. Sustained human chemosignal unconssciously alters brain function. Neuroreport 12, 2391-2394. https://doi.org/10.1097/00001756-200108080-00021.

Jacob, S., McClintock, M.K., 2000. Psychological state and mood effects of steroidal chemosignals in women and men. Horm. Behav. 37, 57-78. https://doi.org/10.1006/hbeh.1999.1559.

Joussain, P., Bessy, M., Faure, F., Bellil, D., Landis, B.N., Hugentobler, M., Tuorila, H., Mustonen, S., Vento, S.I., Delphin-Combe, F., Krolak-Salmon, P., Rouby, C., Bensafi, M., 2016. Application of the European test of olfactory capabilities in patients with olfactory impairment. Eur. Arch. Otorhinolaryngol. 273, 381-390. https://doi.org/10.1007/s00405-015-3536-6.

Kassambara, A., Mundt, F., 2017. Factoextra: Extract and Visualize the Results of Multivariate Data Analyses.

Kilner, J.M., Neal, A., Weiskopf, N., Friston, K.J., Frith, C.D., 2009. Evidence of mirror neurons in human inferior frontal gyrus. J. Neurosci. 29, 10153-10159. https://doi.org/10.1523/JNEUROSCI.2668-09.2009.

Kuukasjarvi, S., Eriksson, C.J.P., Koskela, E., Mappes, T., Nissinen, K., Rantala, M.J., 2004. Attractiveness of women's body odors over the menstrual cycle: the role of oral contraceptives and receiver sex. Behav. Ecol. 15, 579-584. https://doi.org/10.1093/beheco/arh050.

Lê, S., Josse, J., Husson, F., 2008. FactoMineR: an R package for multivariate analysis. J. Stat. Softw. 25, 1-18. https://doi.org/10.18637/jss.v02i05.101.

Lenth, R., Singmann, H., Love, J., Buerkner, P., Herve, M., 2018. EMMEANS: Estimated Marginal Means, Aka Least-Squares Means.

Leyden, J.J., McGinley, K.J., Holzle, E., Labows, J.N., Kligman, A.M., 1981. The microbiology of the human axilla and its relationship to axillary odor. J. Invest. Dermatol. 77, 413-416. https://doi.org/10.1111/1523-1747.ep12494624.

Loos, H.M., Doucet, S., Védérines, F., Sharapa, C., Soussignan, R., Durand, K., Sagot, P., Buettner, A., Schaal, B., 2017. Responses of human neonates to highly diluted odorants from sweat. J. Chem. Ecol. 43, 106-117. https://doi.org/10.1007/s10886-016-0804-x.

Loos, H.M., Schaal, B., Pause, B.M., Smeets, M.A.M., Ferdenzi, C., Roberts, S.C., de Groot, J., Lübke, K.T., Croy, I., Freiherr, J., Bensafi, M., Hummel, T., Havlíček, J., 2025. Past, present, and future of human chemical communication research. Perspect. Psychol. Sci. 20, 20-44. https://doi.org/10.1177/17456916231188417.

Lübke, K.T., Croy, I., Hoenen, M., Gerber, J., Pause, B.M., Hummel, T., 2014. Does human body odor represent a significant and rewarding social signal to individuals high in social openness? PLoS. One 9, e94314. https://doi.org/10.1371/journal.pone.0094314.

Lundström, J.N., Boyle, J.A., Zatorre, R.J., Jones-Gotman, M., 2009. The neuronal substrates of human olfactory based brain recognition. Human Brain Mapp. 30, 2571-2580. https://doi.org/10.1002/hbm.20686.

Lübke, K.T., Hoenen, M., Pause, B.M., 2012. Differential processing of social chemosignals obtained from potential partners in regards to gender and sexual orientation. Behav. Brain Res. 228, 375-387. https://doi.org/10.1016/j.bbr.2011.12.018.

Lundström, J.N., Boyle, J.A., Zatorre, R.J., Jones-Gotman, M., 2008. Functional neuronal processing of body odors differs from that of similar common odors. Cereb. Cortex 18, 1466-1474. https://doi.org/10.1093/cercor/bhm178.

Lundström, J.N., Mathe, A., Schaal, B., Frasnelli, J., Nitzsche, K., Gerber, J., Hummel, T., 2013. Maternal status regulates cortical responses to the body odor of newborns. Front. Psychol. 4, 597. https://doi.org/10.3389/fpsyg.2013.00597.

Lundström, J.N., Olsson, M.J., 2010. Functional neuronal processing of human body odors. Vitam. Horm. 83, 1-23. https://doi.org/10.1016/S0083-6729(10)83001-8.

Mai, J.K., Majtanik, M., Paxinos, G., 2004. Atlas of the Human Brain. Academic Press.

Martins, Y., Preti, G., Crabtree, C.R., Runyan, T., Vainius, A.A., Wysocki, C.J., 2005. Preference for human body odors is influenced by gender and sexual orientation. Psychol. Sci. 16, 694-701. https://doi.org/10.1111/j.1467-9280.2005.01598.x.

Mayer, A.R., Ryman, S.G., Hanlon, F.M., Dodd, A.B., Ling, J.M., 2016. Look Hear! The prefrontal cortex is stratified by modality of sensory input during multisensory cognitive control. Cereb. Cortex 131. https://doi.org/10.1093/cercor/bhw131.

Nováková, L.M., Havlíček, J., Roberts, S.C., 2014. Olfactory processing and odor specificity: a meta-analysis of menstrual cycle variation in olfactory sensitivity. Anthropol. Rev. 77, 331-345. https://doi.org/10.2478/anre-2014-0024.

Olsson, M.J., Lundström, J.N., Kimball, B.A., Gordon, A.R., Karshikoff, B., Hosseini, N., Sorjonen, K., Höglund, C.O., Solares, C., Soop, A., Axelsson, J., Lekander, M., 2014. The scent of disease: human body odor contains an early chemosensory cue of sickness. Psychol. Sci. 25, 817-823. https://doi.org/10.1177/0956797613515681.

Puts, D.A., Gaulin, S.J.C., Verdolini, K., 2006. Dominance and the evolution of sexual dimorphism in human voice pitch. Evol. Human Behav. 27, 283-296. https://doi.org/10.1016/j.evolhumbehav.2005.11.003.

R Core Team, 2013. R: a Language and Environment For Statistical Computing.

Ravreby, I., Snitz, K., Sobel, N., 2022. There is chemistry in social chemistry. Sci. Adv. 8, eabn0154. https://doi.org/10.1126/sciadv.abn0154.

Regenbogen, C., Habel, U., Kellermann, T., 2013. Connecting multimodality in human communication. Front. Hum. Neurosci. 7. https://doi.org/10.3389/fnhum.2013.00754.

Richard Ortegón, S., Fournel, A., Carlos, O., Kawabata Duncan, K., Hirabayashi, K., Tagai, K., Abriat, A., Bensafi, M., Race, B., Ferdenzi, C., 2022. And I'm feeling good: effect of emotional sweat and perfume on others' physiology, verbal responses, and creativity. Chem. Senses. 47, bjac012. https://doi.org/10.1093/chemse/bjac012.

Roberts, S.C., Havlíček, J., Schaal, B., 2020. Human olfactory communication: current challenges and future prospects. Philos Trans R Soc B 375, 20190258. https://doi.org/10.1098/rstb.2019.0258.

Savic, I., Berglund, H., 2010. Androstenol - a steroid derived odor activates the hypothalamus in women. PLoS. One 5. https://doi.org/10.1371/journal.pone.0008651.

Savic, I., Berglund, H., Gulyas, B., Roland, P., 2001. Smelling of odorous sex hormone-like compounds causes sex-differentiated hypothalamic activations in humans. Neuron 31, 661-668. https://doi.org/10.1016/S0896-6273(01)00390-7.

Savic, I., Berglund, H., Lindstrom, P., 2005. Brain response to putative pheromones in homosexual men. Proc. Natl. Acad. Sci. U.S.A. 102, 7356-7361. https://doi.org/10.1073/pnas.0407998102.

Saxton, T.K., Burriss, R.P., Murray, A.K., Rowland, H.M., Craig Roberts, S., 2009. Face, body and speech cues independently predict judgments of attractiveness. J. Evol. Psychol. 7, 23-35. https://doi.org/10.1556/JEP.7.2009.14.

Schaim, B., Montagner, H., Hertling, E., Bolzoni, D., Moyse, A., Quichon, R., 1980. Les stimulations olfactives dans les relations entre l'enfant et la mère. Reprod. Nutr. Develop. 20, 843-858.

Schleidt, M., Hold, B., Attili, G., 1981. A cross-cultural study on the attitude towards personal odors. J. Chem. Ecol. 7, 19-31. https://doi.org/10.1007/BF00988632.

Schmalenberger, K.M., et al., 2021. How to study the menstrual cycle: Practical tools and recommendations. Psychoneuroendocrinology 123, 104895. https://doi.org/10.1016/j.psyneuen.2020.104895.

Sezille, C., Messaoudi, B., Bertrand, A., Joussain, P., Thévenet, M., Bensafi, M., 2013. A portable experimental apparatus for human olfactory fMRI experiments. J. Neurosci. Methods 218, 29-38. https://doi.org/10.1016/j.jneumeth.2013.04.021.

Shamay-Tsoory, S.G., Aharon-Peretz, J., Perry, D., 2009. Two systems for empathy: a double dissociation between emotional and cognitive empathy in inferior frontal gyrus versus ventromedial prefrontal lesions. Brain 132, 617-627. https://doi.org/10.1093/brain/awn279.

Singh, D., Bronstad, P.M., 2001. Female body odour is a potential cue to ovulation. Proc. R. Soc. London B 268, 797-801. https://doi.org/10.1098/rspb.2001.1589.

Singmann, H., Bolker, B., Westfall, J., Aust, F., 2015. Afex: Analysis of Factorial Experiments.

Sorokowska, A., Sorokowski, P., Szmajke, A., 2012. Does personality smell? Accuracy of personality assessments based on body odour. Eur. J. Personal. 26, 496-503. https://doi.org/10.1002/per.848.

Stevenson, R.J., 2010. An initial evaluation of the functions of human olfaction. Chem. Senses 35, 3-20. https://doi.org/10.1093/chemse/bjp083.

Sullivan, R.M., Toubas, P., 1998. Clinical usefulness of maternal odor in newborns: soothing and feeding preparatory responses. Biol. Neonate 74, 402-408. https://doi.org/10.1159/000014061.

Thomas-Danguin, T., Rouby, C., Sicard, G., Vigouroux, M., Farget, V., Johanson, A., Bengtzon, A., Hall, G., Ormel, W., De Graaf, C., Rousseau, F., Dumont, J.P., 2003. Development of the ETOC: a European test of olfactory capabilities. Rhinology. 41, 142-151.

Trebický, V., Delplanque, S., Ferdenzi, C., Fink, B., Jelínková, L., Pátková, Ž., Roberts, S. C., Röder, S., Saxton, T.K., Schwambergová, D., Štěrová, Ž., Fialová, J.T., Havlíček, J., 2023. Cross-modal associations of human body odour attractiveness with facial and vocal attractiveness provide little support for the backup signals hypothesis: a systematic review and meta-analysis. Evol. Human Behav. 44, 19-29. https://doi.org/10.1016/j.evolhumbehav.2022.11.001.

Troccaz, M., Borchard, G., Vuilleumier, C., Raviot-Derrien, S., Niclass, Y., Beccucci, S., Starkenmann, C., 2009. Gender-specific differences between the concentrations of nonvolatile (R)/(S)-3-methyl-3-sulfanylhexan-1-ol and (R)/(S)-3-hydroxy-3-methyl-hexanoic acid odor precursors in axillary secretions. Chem. Senses 34, 203-210. https://doi.org/10.1093/chemse/bjn076.

Winternitz, J., Abbate, J.L., Huchard, E., Havlíček, J., Garamszegi, L.Z., 2017. Patterns of MHC-dependent mate selection in humans and nonhuman primates: a meta-analysis. Mol. Ecol. 26, 668-688. https://doi.org/10.1111/mec.13920.

Wyatt, T.D., 2015. The search for human pheromones: the lost decades and the necessity of returning to first principles. Proc. R. Soc. London B 282, 20142994. https://doi.org/10.1098/rspb.2014.2994.

Zhou, W., Chen, D., 2008. Encoding human sexual chemosensory cues in the orbitofrontal and fusiform cortices. J. Neurosci. 28, 14416-14421. https://doi.org/10.1523/JNEUROSCI.3148-08.2008.