Ilona Croy

Friedrich Schiller University Jena | FSU · Department of Psychology

Olfactory and emotional higher processing pathways share common anatomical substrates. Hence, depression is often accompanied by alterations in olfactory function. These alterations are negative in nature and may involve decreased activation in olfactory eloquent structures or decreased volume in the olfactory bulb (OB). We suggest that olfaction a...

Background: Unmyelinated low-threshold mechanoreceptors-the so-called C-tactile (CT) afferents-play a crucial role in the perception and conduction of caressing and pleasant touch sensations and significantly contribute to the concept of erotic touch perception. Aim: To investigate the relations between sexual desire and sexual performance and t...

Introduction: Touch is important for individuals' subjective well-being, is typically rewarding, and is one of few sensory stimuli which are experienced as pleasant for a rather long time. This study tracked brain activation during slow stroking stimulation of the arm that was applied continuously for 40min - a much longer time than what previous...

Introduction: Touch has been found to entail positive effects in the person receiving it, whereas effects on the person giving touch have previously been unexplored. We investigated whether stroking the partner also is a pleasant experience for the person performing it, and whether it has similar effects on well-being and autonomic nervous functio...

The major histocompatibility complex (MHC, called HLA in humans) is an important genetic component of the immune system. Fish, birds and mammals prefer mates with different genetic MHC code compared to their own, which they determine using olfactory cues. This preference increases the chances of high MHC variety in the offspring, leading to enhance...

Objectives: As part of the quality assurance of inpatient treatment, the severity of the disease and the course of therapy must be mapped. However, there is a high degree of heterogeneity in the implementation of basic diagnostics in psychosomatic facilities.There is a lack of scientifically based standardisation in determining the quality of outco...

Recent cross-cultural and neuro-hormonal investigations have suggested that love is a near universal phenomenon that has a biological background. Therefore, the remaining important question is not whether love exists worldwide but which cultural, social, or environmental factors influence experiences and expressions of love. In the present study, w...

Introduction The human sense of smell has different functions which can be categorized as “food,” “social,” and “environment.” Different questionnaires about the importance of olfaction in adults are available, but little attention has been paid to children and adolescents. Therefore, we aimed to develop a questionnaire about children’s personal si...

Background: Neurophysiological models link dissociation (e.g. feeling detached during or after a traumatic event) to hypoarousal. It is currently assumed that the initial passive reaction to a threat may coincide with a blunted autonomic response, which constitutes the dissociative subtype of post-traumatic stress disorder (PTSD). Objective: Within...

Preterm infants are challenged to adapt to an extrauterine milieu, while their interoceptive system and autonomic regulation capacity is still immature. Caressing parental touch is known to foster parasympathetic regulation in infants by stimulating C-tactile (CT) afferents and in preterm infants, slow stroking stimulation also leads to a heart rat...

The theory of the behavioral immune system (BIS) describes a set of behaviors that protect the individual from infectious diseases and that are motivated by disgust and the perceived vulnerability to disease. As interpersonal touch is one of the most common situations of potential transmission of infectious diseases in our everyday life, it seems l...

There is an ongoing discussion on the relevance of brain reorganization following amputation for phantom limb pain. Recent attempts to provide explanations for seemingly controversial findings—specifically, maladaptive plasticity versus persistent functional representation as a complementary process—acknowledged that reorganization in the primary s...

This study examined how touch role and culture shape affective touch experiences. Germans (N = 130) and Chinese (N = 130) were surveyed once as toucher and once as touchee. For different touch actions, they (a) provided free-text descriptions of what prompts touch, (b) indicated with whom touch feels comfortable, and (c) highlighted areas of touch...

Objective: With the increasing presence of burnout symptoms in clinical and social everyday life, it is necessary to closely examine patients with symptoms of burnout and to classify their respective symptoms in the spectrum of mental disorders. Methods: The sample includes 83 patients who presented themselves in a burnout consultation of the un...

Introduction The Sniffin’ Sticks threshold test is widely used to assess olfactory threshold due to its high reliability and validity. Nevertheless, this test procedure is quite long with an average duration of 10 to 20 min. In study designs that require multiple olfactory threshold tests on short intervals, this could exhaust participants. To coun...

Traditionally, nonverbal behaviors have been understood as coded messages one person sends to another. Following this tradition, social touch has been pursued by asking what it communicates. We argue this question is misleading and ask instead how touch impacts on those giving and receiving it. Indeed, a growing literature investigating gentle phys...

Background: The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we ha...

Although previous research revealed sex differences in affective touch, the implicated processes and the manner in which men and women differ have been left uncertain. Here we addressed this issue in two studies examining sensory and social processes, respectively. Study 1 comprised a series of lab-based experiments in which a robot stroked 214 par...

Touch plays an important role in the development of infants and children. In this review, we highlight the neural conditioning of affective touch and the related physiological responses, especially in the form of parasympathetic activation, pain suppression and stress relief. Based on recent studies, we show that the functionality of a population o...

Bridging the gap between the neurophysiology of C-tactile mediated touch and the psychology of how social touch makes us feel, we present a definition of affective touch as mediated through CT afferents. We clarify how gentle stroking activating the CT system communicates a signal for social exchange. We describe what is already known about the nat...

Generally, three functions are assigned to the sense of smell, namely warning of potential danger, social communication, and importance for eating and drinking. These functions are also reflected in some of the complaints of patients with smell disorders: occurrence of household accidents, inability to smell other people like family members, loss o...

Zusammenfassung Häusliche Gewalt ist laut Studien gesundheitsgefährdend. Ärzt*innen werden von Gewaltopfern als primäre Ansprechpersonen wahrgenommen. Zur Prävention weiterer Gewalt interessiert deren Wahrnehmung von sich selbst als Schlüsselstelle. 1346 bei der Sächsischen Landesärztekammer 2015 gemeldete (Zahn-)Ärzt*innen beantworteten einen Frag...

Zusammenfassung Fragestellung (Teil-)stationäre Psychotherapie ist in Deutschland gut implementiert. Um Wirksamkeitsfaktoren und Effekte besser zu verstehen, sind Effektivitätsstudien notwendig. Diese naturalistische Studie untersucht die Effektivität stationärer und teilstationärer Psychotherapie sowie patientenzentrierte und störungsbezogene Einf...

The recent Coronavirus Disease 2019 (COVID-19) pandemic has led to "social distancing" recommendations from public health organizations, as physical closeness bears the risk of person-to-person Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) transmission. Here, it was explored if interpersonal distance preferences and touch behaviors i...

Major depressive disorder (MDD) is associated with abnormal neural circuitry. It can be measured by assessing functional connectivity (FC) at resting-state functional MRI, that may help identifying neural markers of MDD and provide further efficient diagnosis and monitor treatment outcomes. The main aim of the present study is to investigate, in an...

People differ in their touch preferences and in the ways in which they touch others. People who are blind are particularly sensitive to tactile stimulation as a result of sensory compensation, and sense of touch can support their interpersonal communication. In the article presented here, we aimed to explore whether visual status predicts preferenc...

The study of affectionate touch centers on gentle stroking. Yet friendly physical contact entails other actions, such as embracing, holding, kissing, leaning, petting, squeezing, or tickling. Here, we probed whether these actions are redundant or can be meaningfully differentiated by asking participants (N = 161) to complete a few tasks for each ac...

A wide range of literature connects sex ratio and mating behaviours in non-human animals. However, research examining sex ratio and human mating is limited in scope. Prior work has examined the relationship between sex ratio and desire for short-term, uncommitted mating as well as outcomes such as marriage and divorce rates. Less empirical attentio...

Introduction: Slow brushing over the skin activates C-tactile nerve fibers that transmit pleasant tactile experiences in healthy subjects, leading to an inverted U-shaped velocity dependence of ratings: C-tactile optimal stroking stimulations are rated as more pleasant than slower or faster stimulations. Chronic pain diseases such as postherpetic...

Body odours and their importance for human chemical communication, e.g., in the mother–child relationship, are an increasing focus of recent research. Precise examination of sampling methods considering physiology and feasibility aspects in order to obtain robust and informative odour samples is therefore necessary. Studies comparing body odour sam...

Psychological treatments of posttraumatic stress disorder (PTSD) are associated with non-response rates of up to 50%. This fact highlights the need to identify characteristics of poorer treatment outcome. Among others, previous evidence focused on the role of dysfunctional cortisol secretion which has been related to the development, maintenance an...

Background So far findings on emotional face processing among depressed individuals reveal an inconsistent image, with only some studies supporting a mood-congruent bias in salience processing. Thereby, many results are based on the processing of sad emotions and mostly focused on resting-state connectivity analysis. The present study aimed to targ...

The existence of pheromones in humans is controversial, partly because of definitional difficulties and partly because of the question of possible chemical substances. The synthetic compound Methyl dihydrojasmonate (Hedione) is potent to bind to vomeronasal-type 1 receptors (VN1R1s) and activate limbic areas of the brain in a sex-specific manner. H...

A growing body of research aims at solving what is often referred to as the stimulus-percept problem in olfactory perception. Although computational efforts have made it possible to predict perceptual impressions from the physicochemical space of odors, studies with large psychophysical datasets from non-experts remain scarce. Following previous ap...

Introduction: Patients with chemosensory dysfunction frequently report symptoms of depression. The current study aims to clarify whether the type (smell dysfunction, taste dysfunction, and mixed smell and taste dysfunction), severity, duration, or cause of dysfunction have differential impacts on the symptoms of depression. Methods: 899 patients...

Early detection of patients with late-life depression (LLD) with a high risk of developing dementia contributes to early intervention. Odor identification (OI) dysfunction serves as a marker for predicting dementia, but whether OI dysfunction increases the risk of dementia in LLD patients remains unclear. The present study aimed to explore the inte...

Interpersonal touch behavior differs across cultures, yet no study to date has systematically tested for cultural variation in affective touch, nor examined the factors that might account for this variability. Here, over 14,000 individuals from 45 countries were asked whether they embraced, stroked, kissed, or hugged their partner, friends, and you...

Objective: Olfactory training (OT) represents a therapeutic option for multiple etiologies of olfactory dysfunction (OD) that also benefits normosmic subjects. In this retrospective study, we report the effectiveness of OT and factors associated with relevant changes in olfactory function (OF) in large groups of normosmic participants and patients...

The sense of smell essentially contributes to social communication, guides nutrition behaviour and elicits avoidance towards environmental hazards. Olfactory smell impairment may hence entail severe consequences for affected individuals. Compared with sensory loss in other modalities, reduced olfactory function is often unnoticed by those affected...

Intro The human sense of smell is highly individual and characterized by a strong variability in the perception and evaluation of olfactory stimuli, depending on cultural imprint and current physiological conditions. Since this individual perspective has often been neglected in fMRI studies on olfactory hedonic coding, this study focuses on the neu...

Objective: Women with postpartum mental disorders often have a delayed bonding to their child with negative consequences for the child's development. In several countries it has been demonstrated that a specific mother-child treatment has positive effects on maternal psychopathology and mother-child bonding. Data for German-speaking countries are...

Touch is an irreplaceable contributor to our everyday social life. Interpersonal touch is mediated by a variety of nerve fibers, with Abeta and C-tactile fibers being the most pronounced ones. Slow stroking touch, which targets C-tactile fibers, is experienced as a pleasant sensation and is processed in brain areas, which are involved in reward and...

Slow stroking touch activates C-tactile fibres in the human skin and is typically described as pleasant. Over a longer duration of stroking, affective habituation sets in, indicated by a reduction in rated pleasantness. However, it is not clear whether the group level effect is represented on an individual level. We analyze the stability of individ...

When gently stroked with velocities between 0.1 and 30 cm/s, participants typically rate velocities around 3 cm/s as most pleasant, and the ratings follow an inverted u-shape. This pleasantness curve correlates often, but not always, with the firing rate of unmyelinated C-tactile (CT) afferents, leading to the notion that CT afferents code for the...

Optimization of chances for healthy offspring is thought to be one of the factors driving mate choice and compatibility of the major histocompatibility complex (MHC) is assumed to determine the offspring's fitness. While humans have been claimed to be able to perceive information of MHC compatibility via the olfactory channel, it remains unknown wh...

Introduction Olfaction has an important role in physiological and affective processes, as well as the potential to have profound effects on activities such as sleep and learning. We investigated two commercially manufactured odors (“Deep Sleep” and “Oriental,” from This Works) purported to promote sleep, compared with control odor, where we aimed t...

Background: Olfactory training (OT) represents a therapeutic option for multiple etiologies of olfactory dysfunction (OD) that also benefits normosmic subjects. In this retrospective study, we report the effectiveness of OT and factors associated with relevant changes in olfactory function (OF) in large groups of normosmic participants and patient...

Interpersonal tactile stroking stimulation activates different peripheral nerve fibers, especially C-tactile afferents, which encode pleasant and erotic sensations. Hence, humans typically stroke close interaction partners with velocities that are suited to stimulate C-tactile afferents in the touch receivers’ skin. We aim to replicate this finding...

The Triangular Theory of Love (measured with Sternberg’s Triangular Love Scale – STLS) is a prominent theoretical concept in empirical research on love. To expand the culturally homogeneous body of previous psychometric research regarding the STLS, we conducted a large-scale cross-cultural study with the use of this scale. In total, we examined mor...

Perception of olfactory information is mediated by both bottom-up (from molecules to perception) and top-down (e.g. cross-modal associative learning) processes. Acquired olfactory loss is a frequent disorder which is typically due to alterations in the bottom-up pathway. However, it is unclear how the top-down modulation of olfactory processing is...

Social interpersonal touch is an important part of nonverbal communication and mediates human bonding. However, one’s attitude towards touch is highly individual, and touch is not always perceived as pleasant. For instance, socially anxious people show less touch comfort and higher touch avoidance than socially extroverted people. To investigate wh...

Due to a close functional relation between brain areas processing emotion and those processing olfaction, major depression is often accompanied by reduced olfactory function. Such hyposmia can be improved by regular olfactory training (OT) over several months. As this training furthermore improves subjective well-being, we explored whether OT is a...

Objective The study aimed at investigating the sensitivity to noise and chemosensory environmental stressors as well as the relation to perceived stress, depression and anxiety in subjects with chronic tinnitus as compared to subjects without tinnitus. Methods We included 75 subjects with chronic tinnitus and 75 age and sex-matched subjects withou...

Mothers are able to identify the body odour (BO) of their own child and prefer this smell above other BOs. It has hence been assumed that the infantile BO functions as a chemosignal promoting targeted parental care. We tested this hypothesis and examined whether children's BOs signal genetic similarity and developmental status to mothers. In additi...

Subjective reports and physiological responses provide different appraisals of sensory input. The coherence between subjective and physiological responses to repeated pleasant stimuli remains largely unexplored, and is particularly important in situations where subjective responses are prone to cognitive or contextual bias. Here, we investigate how...

The insular cortex plays a key role in the integration of multimodal information and in interoceptive and exteroceptive processing. For instance, neurons in the central dorsal insula that are active during interoceptive tasks, also show an adaptation to gustatory stimulation. We tested the link between interoception and exteroception for the olfact...

Considerable research has examined human mate preferences across cultures, finding universal sex differences in preferences for attractiveness and resources as well as sources of systematic cultural variation. Two competing perspectives—an evolutionary psychological perspective and a biosocial role perspective—offer alternative explanations for the...

Mothers can recognize their own children by body odor. Besides signaling familiarity, children’s body odors may provide other information relevant to maternal caregiving behavior, such as the child’s developmental status. Thus, we explored whether mothers are able to classify body odors on pre- vs. postpubertal status above chance levels. In total,...

Many studies have investigated the perception of tactile pleasantness over a range of stroking velocities. On average, pleasantness is low at slow (e.g. 0.3 cm/s) and fast (e.g. 30 cm/s) stroking velocities, but is rated highest at velocities between 1-10 cm/s. On a group level, this results in an inverted-U shape pleasantness ratings curve, which...

Specific anosmia is defined as the inability to detect a particular odorant, despite a normal olfactory function. Previous studies reported sex-related difference in detection threshold to steroid odorants, like androstenone or androstadienone during adolescence, and boys showed an increased detection threshold with age. However, such investigation...

Background Migraine is characterized by sensory hypersensitivity and habituation deficits. Slow brushing over the skin activates C-tactile nerve fibers, which mediate pleasant touch and analgesic effects in healthy subjects. As this function is altered in painful conditions, we aimed to examine whether the C-tactile processing is disrupted in migra...

Humans express a wide array of ideal mate preferences. Around the world, people desire romantic partners who are intelligent, healthy, kind, physically attractive, wealthy, and more. In order for these ideal preferences to guide the choice of actual romantic partners, human mating psychology must possess a means to integrate information across thes...

Mate choice lies close to differential reproduction, the engine of evolution. Patterns of mate choice consequently have power to direct the course of evolution. Here we provide evidence suggesting one pattern of human mate choice—the tendency for mates to be similar in overall desirability—caused the evolution of a structure of correlations that we...

Touch is a crucial factor of physiological and psychological health in humans. A lack of touch in contrast is associated with adverse implications on mental health. A new “Longing for Interpersonal Touch Picture Questionnaire (LITPQ)” was developed and tested for its concurrent, predictive, discriminant and face validity as well as its relation to...

Background: Interpersonal touch is a key aspect of human interaction and a usually very comforting experience. For patients suffering from posttraumatic stress disorders (PTSD) caused by interpersonal traumatization, such touch is affectively ambiguous. Methods: In two studies, we investigated the experience and neural processing of various type...