Odors influence several aspects of life, such as thoughts, memories, decisions, and emotions. Numerous studies have shown that human behavior can be affected by odors in different contexts. One such context is social relationships, in which body odors play a role. For example, previous studies have shown that close family members can identify each other’s body odors and prefer these compared to the body odors of non-family members. However, further research is needed to establish how body odors and olfactory functioning affect interpersonal behaviors and intimate relationships. In this thesis, I have conducted three studies highlighting the interplay between intimate relationships and olfaction. The overall purpose of this thesis was to investigate if and how olfaction is related to behaviors in intimate relationships.

Study I tested if a romantic partner’s body odors have stress-altering effects and whether such effects differ depending on individual differences in romantic attachment security. As the practice of smelling a partner’s worn garment has been reported as a self-treatment against stress, my colleagues and I carried out an experiment to determine whether exposure to a partner’s body odor attenuates adult individuals’ subjective discomfort and psychophysiological responses. To induce discomfort and stress responses, participants were exposed to weak electric shocks while smelling their partner’s body odor (experimental condition) and three control odors (control conditions). The results showed that partner body odor had an attenuating effect on subjective discomfort during stress. Additionally, highly attachment-secure participants exhibited attenuated skin conductance specifically when exposed to their partner’s body odor. Thus, study I concluded that partner body odor is a scent of security, especially for relatively attachment-secure adults.

Next, to determine whether olfaction is linked to sexual outcomes in intimate relationships, study II explored associations between self-reported olfactory functioning, on the one hand, and infidelity and sexual well-being, on the other, using a survey design. Our exploratory analyses found that self-reported olfactory function predicted sexual well-being positively and infidelity negatively, while controlling for other relevant socio-demographic variables. These results are discussed from a relationship science perspective, in which one’s intimate partner signifies sexual bonding in addition to caregiving and attachment. Thus, study II suggests that a partner’s body odor might be a scent of monogamy.

Study III summarized the literature on populations with an impaired or total absence of a sense of smell. The interplay between olfaction and intimate relationship variables was examined by reviewing research reports and empirical studies concerning individuals with an impaired sense of smell. My colleague and I provided an overview of how olfactory impairment can impact three types of close social relationships: family relationships, friendships, and romantic relationships. For romantic relationships, which are the main focus of this thesis, three categories were defined in which olfactory impairment can impact close social relationships: eating, social support, and sexuality. Thus, study III concludes that olfactory ability is related to various romantic, intimate relationship behaviors.

In sum, all three studies reported findings highlighting that olfaction (body odors and olfactory functioning) is related to intimate relationships. The results from the three studies are discussed via theoretical frameworks concerning the sense of smell, romantic relationships, and attachment. The thesis concludes that olfactory functioning and the experience of body odors are meaningful for intimate relationships and, as such, also for various behaviors in these relationships.

Extensive research has highlighted how one's attachment style influences the development and maintenance of romantic relationships. Disgust is a construct that conceptually overlaps with attachment style given both include elements of behavioral avoidance. However, no previous study has examined how one's attachment style may influence disgust-based avoidance of intimacy in romantic relationships. Therefore, the aim of the current study is to determine if adult attachment style is associated with olfactory disgust ratings towards eight body odor (BO) sources from their partner, previous partner, or others. The results revealed that disgust ratings of a partner's BO differed depending on attachment style. Specifically, the participants with a dismissing-avoidant attachment style rated their partner's BO as more disgusting than the secure, fearful-avoidant, or preoccupied styles. Moreover, participants with a dismissing-avoidant attachment style rated their partner's and strangers' BO equally disgusting whereas those in the other attachment groups rated strangers' BO as more disgusting than their partner's. 

The study aimed to investigate if hentai consumers differed from other pornography consumers regarding their attachment style, attraction to, and desire for romantic relationships with anime characters and humans. Pornography consumers were categorized into three groups. The first group consumed both hentai and human pornography (hentai consumers), the second consumed human pornography but not hentai (non-hentai), and the third did not consume hentai or human pornography (non-porn). Two hundred and eight participants completed an online study that involved self-report surveys and an image rating task. The results revealed that hentai consumers did not differ from non-hentai or non-porn consumers on avoidant attachment. However, among females, hentai consumers were higher on anxious attachment compared to non-porn consumers. For the image rating task, hentai consumers rated anime characters more attractive than non-hentai and non-porn consumers. However, there were no group differences for the image ratings of real people. Hentai consumers indicated stronger romantic desire towards anime characters compared to non-hentai and non-porn consumers; there were no group differences in romantic desire for humans. The findings highlight the importance of differentiating individuals who consume hentai and those who do not.

Previous studies have shown that olfactory function plays an essential role in the bonding of a romantic relationship. Body odors, in particular, seem involved in both mate choices and other intimate behaviors. Our sense of smell is also crucial to detect possible pathogen threats, by activating a suitable disgust reaction. Previous studies have shown that disgust sensitivity is negatively related to sociosexuality, and disgust generally inhibits our sexual drive. In the present study, we explored the possible relation between olfactory function, pathogen disgust sensitivity, sociosexuality, sexual well-being, and infidelity through a web survey. Our exploratory analyses found that, in a large Italian sample (N = 1107), among those in a stable relationship, self-reported olfactory function predicted sexual well-being (p < .05) and negatively predicted infidelity (p < .05) when controlling for other relevant sociodemographics variables. Moreover, the relation between self-reported olfactory function and sexual well-being was mediated by pathogen disgust sensitivity. Although significant, these results must be interpreted with caution, because the effect sizes were small.

Olfactory impairment is one of the more unique symptoms of COVID-19 infection and has therefore enjoyed increased public attention in recent months. Olfactory impairment has various implications and consequences ranging from difficulty detecting dangerous pathogens to hindering social functioning and social behaviors. We provide an overview of how olfactory impairment can impact 3 types of close social relationships: family relationships, friendships, and romantic relationships. Evidence is divided into several categories representing potential mechanisms by which olfactory impairment can impact close social relationships: bonding disruptions, decreased social support, missed group-eating experiences, hygiene concerns, and altered sexual behaviors. We conclude with a discussion of emerging future research questions.

Individuals in healthy romantic relationships gain significant benefits to their psychological wellbeing and physiological health. Notably, the majority of relationship research has focused on how adult attachment influences these relationship outcomes while the role of olfaction remains an emerging research focus. The aim of the current study was to bring together these seemingly unrelated factors–attachment and olfaction–in an online quasi-experimental design. The participants were 401 undergraduate students, predominantly females, ranging in age from 17 to 70 years. Participants completed a battery of questionnaires that evaluated their attachment tendencies, olfactory ability and experiences in romantic relationships. Results indicated that attachment insecurity, across both attachment anxiety and avoidance, was associated with decreased olfactory functioning for females. These findings provide preliminary evidence that olfaction is related to romantic relationship maintenance and suggests that body odors could be fundamental for evoking the attachment system. These findings also elicit enticing new avenues of research which can assist psychologists to provide targeted treatments to individuals with olfactory deficits and insecure attachment tendencies.

The roots of psychopathology frequently take shape during infancy in the context of parent-infant interactions and adversity. Yet, neurobiological mechanisms linking these processes during infancy remain elusive. Here, using responses to attachment figures among infants who experienced adversity as a benchmark, we assessed rat pup cortical local field potentials (LFPs) and behaviors exposed to adversity in response to maternal rough and nurturing handling by examining its impact on pup separation-reunion with the mother. We show that during adversity, pup cortical LFP dynamic range decreased during nurturing maternal behaviors, but was minimally impacted by rough handling. During reunion, adversity-experiencing pups showed aberrant interactions with mother and blunted cortical LFP. Blocking pup stress hormone during either adversity or reunion restored typical behavior, LFP power, and cross-frequency coupling. This translational approach suggests adversity-rearing produces a stress-induced aberrant neurobehavioral processing of the mother, which can be used as an early biomarker of later-life pathology. The roots of psychopathology take shape during adverse parent-infant interactions, shown through infant attachment quality. Using rodents, the authors show that blunted infant cortical processing of the mother determines attachment quality through a stress hormone-dependent mechanism.

Body odors are universal elicitors of disgust, a core emotion that plays a key role in the behavioral immune system (BIS) - a set of psychological functions working to avoid disease. Recent studies showed that body odor disgust sensitivity (BODS) is associated with explicit xenophobia and authoritarianism. In the current experimental pre-registered study (), we investigated the association between olfactory pathogen cues, BODS and implicit bias toward an outgroup (tested by an implicit association test). Results show that BODS is positively related to implicit bias toward an outgroup, suggesting that social attitudes may be linked to basic chemosensory processes. These attitudes were not influenced by background odors. Additionally, BODS was related to social, but not economic conservatism. This study extends the BIS framework to an experimental context by focusing on the role of disgust and body odors in shaping implicit bias.

Early life experiences are essential for a healthy development according to both human and animal research. From the attachment literature the primary caregiver has always been the center of attention in predicating outcomes in later development of the child.

The attachment literature also highlights two functions that the caregiver implicit activate, the safe haven and the secure base functions. Safe haven function is when the infant can depend on the caregiver for comfort and relief if stressed. The secure base function is described as when the caregiver works as a platform for the child to explore. This latter function has the intent to describe the infant’s balance between two behaviours; exploration and proximity seeking.

In this study we are linking the described attachment behaviour system with a neurobiological approach of measuring cortical local field potential (LFP) oscillations in rat pups. By using an experimental setting with both measures of behaviour and LFP where the pup interacts with the mother and a stranger we evaluate the secure base function. In addition, we are applying the Scarcity-Adversity Model of maltreatment to disentangle critical attachment disruptions. We are discovering differences in the two different groups of rat pups (control and maltreatment) and are reflecting on these results both on an attachment behavioral and neurobiological developmental level.

Why are certain individuals persistent in opposing immigration? The behavioral immune system framework implies that a psychological mechanism, which adapted to detect and avoid pathogen threats, is also reflected in contemporary social attitudes. Moreover, prejudice towards outgroups might be partially driven by implicit pathogen concerns related to the perceived dissimilarity with these groups' hygiene and food preparation practices. Disgust, a universal core emotion supposedly evolved to avoid pathogen threats, as well as olfaction, both play a pivotal role in evoking disgust. In an online study (N = 800), we investigated whether individual differences in body odor disgust sensitivity (BODS) correlate with negative attitudes towards a fictive refugee group. The data analysis plan and hypotheses were preregistered. Results show that body odor disgust sensitivity is associated with xenophobia: BODS was positively associated with negative attitudes towards the fictive group. This relationship was partially mediated by perceived dissimilarities of the group in terms of hygiene and food preparation. Our finding suggests prejudice might be rooted in sensory mechanisms.