The Sensation Was So Agreeable That I Resolved to Try Again.

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Agreeable Smellers and Sensitive Neurotics – Correlations among Personality Traits and Sensory Thresholds

• Ilona Croy,
• Maria Springborn,
• Jörn Lötsch,
• Amy N. B. Johnston,
• Thomas Hummel

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• Published: Apr 27, 2011
• https://doi.org/10.1371/journal.pone.0018701

Figures

Abstruse

Correlations between personality traits and a wide range of sensory thresholds were examined. Participants (N = 124) completed a personality inventory (NEO-FFI) and underwent cess of olfactory, trigeminal, tactile and gustatory detection thresholds, also every bit examination of trigeminal and tactile hurting thresholds. Significantly enhanced odor sensitivity in socially amusing people, significantly enhanced trigeminal sensitivity in neurotic subjects, and a tendency for enhanced hurting tolerance in highly conscientious participants was revealed. It is postulated that varied sensory processing may influence an individual's perception of the environment; particularly their perception of socially relevant or potentially dangerous stimuli and thus, varied with personality.

Citation: Croy I, Springborn Thousand, Lötsch J, Johnston ANB, Hummel T (2011) Agreeable Smellers and Sensitive Neurotics – Correlations among Personality Traits and Sensory Thresholds. PLoS ONE half dozen(four): e18701. https://doi.org/10.1371/journal.pone.0018701

Editor: Hiroaki Matsunami, Duke University, The states

Received: September 27, 2010; Accepted: March 15, 2011; Published: April 27, 2011

Copyright: © 2011 Croy et al. This is an open-access article distributed nether the terms of the Artistic Commons Attribution License, which permits unrestricted utilise, distribution, and reproduction in whatever medium, provided the original author and source are credited.

Funding: The authors were free to directly analysis and reporting without any influence from sponsors. There was no editorial direction or censorship from any sponsors.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Personality research often explores the evolution of and influences on personality traits, characteristics that are sometimes defined equally "enduring tendencies or habitual patterns of beliefs, thought, and emotion" [ane]. Many models of personality, exploring and defining specific traits have been adult, some more complex than others. The five-factor model of personality [two] enables a description of human personality in a relatively economical way. Information technology is intended to supply a comprehensive taxonomy of traits using simply five basic categories- extraversion, neuroticism, agreeableness, openness and conscientiousness and thus provides opportunity to effectively explore potential influences on the development of personality traits and their relationships with other parameters such as sensory ability.

Indeed, i of the most interesting areas in current personality research deals with the problem of how personality may exist shaped during development. What induces people to differ from each other in the way they think, experience or acquit in sure situations? The last few decades of personality inquiry and clinical praxis take seen the emergence of nature-nurture-interaction hypotheses in respond to such key developmental issues [three], [iv]. These suggest that basic tendencies are constitutionally predisposed just are likewise developed and shaped during experiences with and inside the environment. Thus, the environs enables subtle shaping of obviously underlying genetic components of personality.

Prior to this study virtually no research has explored the influence of variation in sensory thresholds on individual differences in personality, even though enquiry has demonstrated that there are pregnant private differences in visual, auditory, olfactory and gustatory capacity (due east.grand. [5], [six], [7]) besides as in tolerance to hurting ([eight], [nine], [10]. Thus, this study set out to systematically examine whether at that place maybe relationships between sensory thresholds and inter-individual personality differences.

Sensory 'constitution' could exist an private variable associated with and helping to form personality characteristics. This hypothesis is seated in the notion that people do not have an objective picture of the globe surrounding them, but rather, a person-specific filtered one. The varying capacities of peoples' sensory systems would form one part of a possible 'sensory-filter' system applied by all to their perception of their surroundings. Such a stable, rigid filter could greatly influence an individual's perception of the world and therefore influence their thoughts, behavior and emotions relative to their surroundings. In addition, the attention given past an individual to a detail stimuli or to a item form of sensory input could also shape such a 'sensory-filter'. Attention to particular kinds of sensory stimuli could exist modulated by many factors including by electric current emotional state. For example, people suffering from posttraumatic stress disorder (PTSD) take been shown to process unpleasant, potential harming, stimuli in a preferred manner [11], [12].

'Thought' experiments tin exist used to graphically illustrate this 'sensory-filter' concept. If one lived with increased strong feelings of hurting, 1 might perceive the world as a rather unpleasant place. A major behavioral motivation for such a person would include reduction of hurting, so that harm abstention would become highly important and fifty-fifty prevalent. Indeed there is testify suggesting that neuroticism is related to pain perception ([ix], run into below).

Another straightforward example to follow is that of the influence of blindness on personality. Ammerman and colleagues (1986) provided evidence demonstrating that blind adolescents tended to be more than dependent on others, more introverted and to exhibit enhanced feet than sighted adolescents. This might be a very appropriate adjustment to the disease, ensuring that they develop and utilise reliance on others to assistance them safely navigate their environment [thirteen]. The electric current experiments explore the hypothesis that non but the full loss of i of the senses could and should induce personality change, but that intra-private variability occurring in every sensory system, and leading to intra-private differences in sensory capacity for each sense, may also influence personality.

Goldman and colleagues explored a very similar hypothesis when they attempted to correlate auditory threshold in 42 student participants with measurements of sensation seeking [14]. They reported that sensation seekers were significantly less sensitive to auditory thresholds than the normative population; supporting the notion that there is an influence of the capacity of the auditory arrangement on personality. Unfortunately, this study used ascending instead of random choice thresholds of testing, so the influence of decision-making processes on auditory threshold remains somewhat unclear. However, even when mindful of this proviso, their interpretation of their results was that people with depression auditory sensitivity might be in search of stimulation, supporting a possible office of sensory-filtering in externalization of personality traits.

When because the processing steps that determine how people perceive the environment, it seems plausible that chapters for sensory processing could influence the 'moving picture of the earth', people build and thus, the development of patterned behavioral responses to 'that world'. Relationships between sensory systems and personality might play out through personality development as discussed in a higher place. Alternatively, the capacities of sensory systems and instigation of personality traits may share the same underlying genetic origins. In any case, looking at ways personality traits might relate to sensory variables is a valuable beginning step in addressing such questions.

The aim of the present study was to systematically explore coherence between a wide range of sensory thresholds and personality traits. The study used the NEO-FFI to measure personality dimensions. Information technology is based on a v-factor-model of personality model, a widely accepted and oftentimes validated theory for description of personality [2], [15]. Concomitant measurement of sensory thresholds focused on assessment of olfactory, trigeminal chemosensory, electric and gustatory detection thresholds, every bit well every bit establishing individual's trigeminal chemosensory and electric pain thresholds. The conclusion to attempt correlation of these senses with personality was primarily driven by the wealth of experience in our laboratory with detailed and precise determination of chemosensory perception. To ensure the reader's familiar with these senses, they are discussed in some detail below.

Chemosensory perception including olfaction, sense of taste and trigeminal perception are included among the evolutionarily 'oldest' senses. Ecology cues, typically processed through the olfactory channel are ofttimes associated with perception of food, just 'danger' and 'social' stimuli can also be communicated using olfaction [16]. Olfaction as well seems to play a key part in providing data nigh the emotional country of others [17], [eighteen]. In a contempo experiment Prehn-Kirstensen and colleges presented anxiety-induced and sport-condition sweat samples to 28 participants and collected fMRI data during presentation. They showed that the 'anxiety' sweat was processed in areas related to empathy, while the 'sport condition' sweat was not [17]. Given the social communication function of the olfactory system, i might expect personality traits, related to social relationships, to be influenced by the effective sensitivity of olfactory arrangement. We could therefore postulate that conjuration, a trait strongly related to social skills, would be positively correlated with olfactory sensitivity.

Gustatory perception is besides activated during eating, so that potentially dangerous nature of the food (often associated with the bitterness of the food), and also the nutrition value of nutrient (sweetness) can be estimated. Information technology is not immediately clear how an enhanced or reduced ability to perceive food (oral) stimuli –within a normal range – would influence personality. There is evidence, at to the lowest degree in very immature children, that presentation of sweet stimuli tin can human activity as a form of analgesia, reducing the negativity and stress associated with medical procedures [19]. Thus, to get a broad overview of different senses, their variability and potential interrelationship of personality, gustation was also explored.

Receptors of the trigeminal chemosensory channel too prevarication within the nasal cavity. Stimulation of this system in a salubrious person leads to perception of a burning/stinging sensation. This typically occurs while eating spicy foods, but besides during the detection of potential dangers, such equally fires.

Finally, stimuli candy through electrical cutaneous channels includes bear upon and tactile information, but also data almost potential risks such as chemical and/or mechanical harm of the skin. Thus, nosotros likewise analyzed pain perception by presenting increasing stimuli to the trigeminal and electric cutaneous channels. For both, the trigeminal chemosensory besides as the electric cutaneous channels we could hypothesize enhanced neuroticism in people with loftier sensitivity to potentially painful and/or dangerous stimuli, both conceptually and as well on the footing of some, albeit limited, evidence.

There are sporadic studies dealing with sensory sensitivity of the systems described above and personality. In ane study, hurting tolerance to cold water was examined in 56 Japanese students and correlated with their performance in the Maudsley Neuroticism and Extraversion Scales and in the Manifest Anxiety Scale [10]. Results indicated a significant coherence between hurting sensitivity and high neuroticism and anxiety values, and with low extraversion values [10].

In a recent written report, Paine and colleagues induced visceral and somatic pain in eighteen healthy volunteers by amplification of an oesophageal balloon or application of nail-bed pressure, respectively. During the 'pain application', measurements of cardiovascular variables including blood pressure and also skin conductance were obtained. Additionally participants were asked to complete the 'Big-Five' Inventory. Pregnant coherence between enhanced neuroticsm and decreased extraversion was recorded, with meaning, pain-related, cardiac vagal tone slope modify. The authors interpreted this result in the context of evolution of functional visceral pain syndrome, which is overrepresented in highly-neurotic patients [9].

Generally, enquiry exploring sensory detection thresholds and their relationship with personality is relatively rare. Besides the connexion between sensation seeking and auditory threshold, described in the study of Goldman and colleagues above [fourteen], we could find only ii studies dealing with personality and taste thresholds. In ane study Zverev and Mipando (2008) obtained taste detection thresholds in 60 volunteers and correlated these with the results from application of the Eysencks Personality Inventory. They found no coherence betwixt taste sensitivity and determined personality traits [20]. In another written report published in 1967 Corlis and colleges compared the personality of students with loftier and low quinine taste sensitivity [21]. They plant quinine-sensitive participants to be more "intuitive" than the insensitive tasters.

In an older study, 140 students were asked to complete a questionnaire scoring personality on the intraversion-extraversion scale and to performing a test examining olfactory sensitivity [22]. In this study a pocket-size, but significant, correlation (r = 0.23) between extraversion and enhanced olfactory sensitivity was reported. In another publication reporting two studies with a rather small sample sizes of 12, respectivly 26 participants, neuroticism, merely non extraversion was found to be related with enhanced olfactory sensitivity to some, but not to all of the analysed odors [23]. An intreguing report from Zhou and colleagues explored olfaction and emotional abilities [18]. They asked 22 pairs of female roommates to identify the torso odor of their roommate from one of three t-shirts. The higher the women scored on a self-rating questionnaire measuring emotional awareness, the improve they were able to perform the job, implying a potential link betwixt emotional awareness and olfactory discrimination threshold.

Thus, the testify linking personality and chemosensory sensitivity is mixed – particularly every bit there is little evidence linking sensitivity in one chemosensory modality with that of another chemosensory modality [24]. The current study was adult to explore multi-modal chemosensory abilities in people and potential relationships between specific chemosensory modalities and personality traits.

Methods

Ethics Argument

The written report followed the Annunciation of Helsinki on Biomedical Inquiry Involving Man Subjects and was approved by the Ideals Committee from the University of Dresden Medical School. All participants provided written informed consent.

Participants

A full of 124 good for you subjects (41 men, 85 women, aged eighteen to 52 years, hateful = 24 years; standard departure = 5) participated in this study; most of whom were graduate students or members of the Technical University of Dresden Medical Schoolhouse. Completion of a detailed medical history form past each participant enabled confirmation of their good physical wellness. Demographic data from the participants is shown in Table ane. Data from these participants has previously analyzed with respect to correlations between the dissimilar sensory organization [24], only non with respect to individual differences in personality.

Materials and Procedure

Following the taking of a detailed medical history, participants were asked to complete the German form of the NEO-FFI questionnaire [25], [26]. Subsequent assessment of sensory thresholds was conducted with the testing sequence balanced across all participants. Participants were given breaks of 5 to 10 min between the various tests.

NEO-FFI Questionnaire.

Personality was assessed using the reliable and validated NEO-FFI questionnaire based on the 'BIG FIVE' theory of personality. The self-rating questionnaire consists of sixty different statements which prompt responses on a 5-point Likert-scale varying from "full disagreement" to "total agreement". A sum score for each of the five personality dimensions "neuroticism", "extraversion", "openness for new experiences", "agreeableness" and "conscientiousness" is used to build a personality contour. Average time for completion of the questionnaire is x minutes.

Threshold testing.

To prevent visual cues from prompting responses during chemosensory measurements, participants were obliged to vesture an eye mask during testing. Detection thresholds were obtained using a three-culling, forced-choice, modified staircase method of stimulus presentation (see below). The thresholds assessed were: trigeminal chemosensory (CO₂), olfactory (PEA – phenyl ethyl alcohol), gustatory for sour (citric acrid) and salty stimuli (NaCl), and cutaneouos electric stimuli. Pain thresholds were obtained for cutaneous electric and trigeminal chemosensory stimuli. Beginning with the detection threshold, stimulus intensity was increased (linearly) upward to the betoken when the participant indicated that the stimulus became noticeably painful. This procedure was repeated at to the lowest degree once. If the 2d guess differed from the showtime by more than 1 step, the process was repeated a 3rd time. An average of the two estimates (or, where 3 measurements had been taken, the average of the three estimates) was used equally the final measure.

Trigeminal chemosensory thresholds.

A short gaseous CO_ii stimulus was delivered via an olfactometer (Olfactometer OM2S, Burghart Instruments, Wedel, Federal republic of germany) to the participant's nasal mucosa (duration 500 ms, ascension time <20 ms; total flow 6 50/min). Measurements started at a concentration of 3% v/v CO₂. Concentrations were increased stepwise by 3% CO₂ up to a concentration of 30% v/v, thereafter concentration steps of v% CO₂ were used. An interval of approximately xv–20 s was provided between each presentation of individual stimuli.

For detection threshold, a three-alternative forced-selection task and a staircase paradigm starting at three% CO₂ concentration were used. One CO₂ stimulus and 2 blanks (room air) were presented at each dilution footstep. Subjects were asked to indicate whether they perceived a stimulus. Two successive correct identifications or one incorrect identification triggered a reversal of the staircase. Detection thresholds were estimated as the mean of the final four out of seven staircase reversals. Afterwards cess of the detection threshold, each participant's pain threshold was adamant. CO_two concentrations were increased until the participant indicated that the stimulus became painful. This procedure was repeated at least once. If the 2nd judge differed from the outset approximate past more than than i concentration pace, the process was repeated once more. An average of the two estimates (or, in case where iii measurements had been taken, the average of the three estimates) was used as the determined pain threshold.

Electric thresholds.

Electrical thresholds were obtained using a abiding voltage device (PowerLab 26T; ADInstruments, Spechbach, Federal republic of germany). Stimuli were applied with a stimulating bar electrode, placed at the forehead. Shock intensity was increased from 0 to 20 mA in steps of 0.i mA.

For determination of detection thresholds a 3-alternative forced choice paradigm was used, like to that described above. Subjects received three stimuli per trial (ii with 0 mA, one with electrical stimulation; stimulus duration 2 ms; interstimulus interval between the triplet of stimuli: 2–4 south; interstimulus interval between triplets: approximately 15–20 s). Two successive correct identifications of the impulse or one incorrect identification triggered a reversal of the staircase. Tactile detection was represented by the boilerplate voltage determined by the mean of the last four out of seven staircase reversals. After assessment of the detection threshold, hurting threshold was obtained. The electric stimuli were increased stepwise up to the point when the participant indicated that the impulse was perceived as painful. This procedure was replicated at least once. If the second judge differed from the get-go guess past more than 1 intensity footstep, the procedure was repeated again. An average of the ii or 3 estimates obtained was used to depict pain threshold.

Olfactory threshold.

Olfactory detection threshold was assessed birhinally with the "Sniffin' Sticks" test (Burghart Instruments, Wedel, Germany) [27], [28]. In this validated test odors are presented in felt-tip pens. For odour presentation, one pen at a time – with the cap removed - is placed directly in front of the nostrils at a distance of approximately 1 to 2 cm (for a detailed clarification of the examination procedures please run into [27]). Odor thresholds were obtained for the rose-like odour phenyl ethyl booze (PEA) presented in xvi one∶2 dilution steps starting from a 4% solution. PEA is ordinarily used for olfactory threshold testing and correlations between PEA thresholds and Butanol thresholds are acceptable loftier [29].

Using a three-alternative forced-choice chore and a staircase paradigm starting at low PEA concentrations, one pen with the odorant and two blanks were presented at each dilution pace. Again, ii successive correct identifications or one incorrect identification triggered a reversal of the staircase. Odor detection threshold was represented by the mean of the last four out of seven staircase reversals.

Gustatory thresholds.

Gustatory detection thresholds were assessed for sour (citric acid) and salty (NaCl) stimuli. Administration of the taste stimuli was based on the principles used with the "Taste strips" [30] where i cm² of filter newspaper is impregnated with a tastant. The dried filter papers are so applied to the natural language. In the current exam, based on extensive previous feel with the gustation strips [31], the strips applied to the tongue were impregnated with 14 dilutions each of salty and sour stimuli, starting from everyman concentrations of 0.3 g/ml citric acid and 0.25 g/ml NaCl Dilutions were made in geometric series of 1∶three with water equally the solvent. Using a 'whole-mouth' epitome, participants received 3 strips with merely ane containing tastant at a given concentration. Their task was to describe whether the strip had a 'taste' or not. After each stimulus presentation, the participants rinsed their oral fissure with fresh tap water. Where participant'south response was correct 3 times in a row, the dilution stride was noted down every bit gustatory threshold.

Results

Data was analyzed using the SPSS 17 Software (SPSS Inc., Chicago, Ill., United states). For comparison of our sample with the German normative sample [25] raw data of the NEO-FFI personality dimensions were converted into T-scores and then analyzed using unmarried t-test.

Pearson's correlation assay betwixt the personality dimensions and the assessed sensory thresholds from the whole sample was performed. Bonferroni-Holm- corrections for multiple comparisons adjusted for dependent measurements have been performed for all correlations (chiliad = 10) [32]. To clarify the independent contribution of the sensory capacity measurements to the personality trait values, linear multiple regression analysis was also performed.

Personality traits

Results from the questionnaire are provided in Table 1. Participants scored significantly lower on the neuroticism scores (p = 0.005) and significantly higher on the agreeableness (p<0.001) and on the conscientious-scale (p<0.001) than the German normative sample [25]. This is probably related to the skewed (University) population who fabricated up the exam sample.

Correlation between sensory thresholds and personality traits

Correlations between sensory thresholds and personality traits are presented in Tabular array 2. A modest, but meaning positive coherence was observed between conjuration and odor detection sensitivity (r = 0.269, p_corrected  = 0.02, see Figure 1). A small, but significant positive correlation was evident between neuroticism and trigeminal chemosensory detection sensitivity (r = 0.272, p_corrected  = 0.05, see Effigy 2). A positive correlation was also axiomatic between assessed neuroticism and both pain thresholds (trigeminal: r = 0.225 p_uncorr  = 0.021; electric cutaneous: r = 0.184, p_uncorr  = 0.042), only these correlations did not survive corrections for multiple measurements. Without correcting for multiple measurements, there were significant negative correlations between conscientiousness and trigeminal chemosensory perception sensitivity (r = −0.213, p_uncorr  = 0.28) and with electrical cutaneous hurting sensitivity (r = −0.181, p_uncorr  = 0.46), but both correlations vanished on correction for multiple measurements.

No significant coherence was observed between the value of the extraversion and openness personality traits in the NEO-FFI questionnaire and whatsoever of the threshold tests. For the gustatory channel no significant correlation with the value of the personality traits was observed.

Sensory predictors of the personality traits

Multiple regression analysis revealed 2 models that significantly predict agreeableness (see Table iii). Model ane included only the olfactory detection thresholds (p = 0.046), while model two included olfactory detection thresholds and trigeminal chemosensory sensitivity (p = 0.04). For trigeminal chemosensory merely the hurting threshold, non the detection threshold, contributes significantly to the model. Two meaning models could exist used to predict neuroticism values (come across Tabular array 4). Model one included trigeminal chemosensory sensitivity (p = 0.022), in which only detection threshold, not pain threshold, contributes significantly. Model two too contains electrical cutaneous sensitivity (p = 0.02), yet, neither of these variables alone significantly directs issue.

No pregnant model of the sensory variables predicting the personality traits conscientiousness, extraversion and openness was adamant.

Discussion

The principal consequence of this written report, confirming our initial hypotheses, was that at that place is an apparent relationship betwixt certain personality traits and sensory capacities. This finding supports the notion that sensory capacity may provide a filter through which we perceive the world, and that this filter may influence the picture we receive of the world. Interestingly the diverse chemosensory systems seem to be of differing importance in helping to influence personality traits. We found no coherence between personality traits and gustatory modality (mainly related to eating) merely meaning coherence between personality traits and olfactory, trigeminal sensory and electrical cutaneous modality; systems ordinarily thought to be related to detection of social cues and sensation of danger. This concurs with results of a recent study that besides found no coherence between gustatory sensitivity and personality [20]. It seems reasonable that sensory systems processing environmental cues such every bit social relationships and potential danger should more strongly influence personality shaping than systems that processing cues related to eating. Moreover, when analyzing the information describing the different thresholds we tested for each individual, nosotros institute no overall correlation between these thresholds. So information technology seems that in that location is no such thing as a "by and large sensitive" person, but rather that people differ quite widely in the sensitiveness of their specific chemosensory modalities [24].

We interpret the correlation between enhanced olfactory property sensitivity and agreeableness to betoken that high olfactory sensitivity might mirror increased involvement in social matters including social odors. Multiple regression analysis additionally revealed one significant model predicting agreeableness values with olfactory detection and trigeminal chemosensory sensitivity. As we did not discover a clear significant correlation between conjuration and trigeminal chemosensory pain sensitivity, we rather suspect a possible statistical suppression effect here.

Amusing people can also be described as "cooperative, considerate, empathic, generous and kind" people, and thus this personality trait indicates the power to course congenial social relationships with others [iv]. Equally odors have the potential to communicate information most the emotional land of others [17], an enhanced ability to detect such odors could back up empathy and social awareness in recipients. The contempo study showing female roommates who are better able to place their roommate also score higher in assessments of emotional competence, farther supports this hypothesis [18].

Wider exploration of sex differences in emotional and in olfactory competence shows similar patterns of gender response. Women do not just have more often than not higher agreeableness scores [33], but too typically outperform men in odor processing abilities [34]. Interestingly, previous research showed coherence between effective social function and olfactory functioning in people with autism. In fact, autistic children with especially high social damage had the lowest levels of olfactory perception [35].

Trigeminal chemosensory detection sensitivity has been plant to be related to enhanced neuroticism. Ecology cues that are typically processed using this modality are strongly related to 'danger' signals. In contrast to olfactory or gustatory stimulation, trigeminal stimulation is described as becoming painful through to becoming unbearable at high concentrations. While the data described herein, indicating enhanced trigeminal and electrical hurting sensitivity occurring in conjunction with higher levels neuroticism did not survive correction for multiple measurements, it all the same led in the very same direction. Use of a greater number of participants drawn from wider social groupings may take enabled this relationship to withstand detailed statistical comparison. Other studies have likewise reported relationships betwixt pain sensitivity and evident neuroticism [ix], [ten]. Neuroticism is a trait "that encompasses the tendency to experience the world as pitiful or threatening" [4]. Based on our results we would argue that participants who are very sensitive to potentially dangerous and inherently painful trigeminal stimuli maybe more likely to translate the world equally an unpleasant ane, which would consequence in enhanced neuroticism scores. Although this explanation would seem eminently plausible, correlation analyses practice not allow causal interpretation. It would be equally plausible to explore this blueprint the other way around: That is, people who score high on "neuroticism" may tend to subjectively anticipate experiences as negative or potentially damaging [36], and could, therefore, be more than likely to detect potentially unpleasant stimuli. Results concurring with this hypothesis have been described in a subgroup of people with pathologically negative emotional expression – women with post-traumatic stress disorder [11]. Significantly negative correlations were described betwixt women with enhanced PTSD scores and upshot-related potentials evoked in response to odors and also the trigeminal stimulant CO2. Acme latencies for CO_two and for a very unpleasant odor were reduced in the population showing more extreme PTSD-related responses, indicating a preferred processing of unpleasant stimuli in those patients.

A rather surprising coherence between the 'conscientious' trait and reduced trigeminal chemosensory sensitivity was evident in these results, besides as a correlation between the 'conscientious' trait and reduced hurting sensitivity in the trigeminal chemosensory. The same trend was evident betwixt the 'conscientious' trait and electrical cutaneous sensitivity (come across table 2). Neither significant correlation, nor the credible tendency, was axiomatic following correction for multiple measurements, so cautious estimation of these results must be practical. Withal, both pain sensitivity measurements showed the same tendency for enhanced pain tolerance in more conscientious participants, and thus it warrants some consideration. Pain thresholds were assessed using an ascending scale until the participant indicated the stimulus as painful. This is in contrast to detection thresholds which were assessed in a multiple option manner, and thus, are relatively difficult to influence. Moreover, a motivational component is very likely to modulate the issue of pain threshold measurements. Therefore, the patently enhanced pain tolerance in highly conscientious participants perhaps associated with the enhanced motivation these people take to perform a task 'well'. Desire for compliance with study results and a motivation to 'please' and practise 'the right affair' must exist carefully considered when dealing with the personality trait conscientiousness and its impact on hurting perception.

When comparing sensory chapters with personality, there are several potential biases which must be carefully considered. Firstly, neither sensory capacity nor personality are observed direct. To test these sensory capacities psychophysiological measurements were used which, every bit careful one collects and examines them, peradventure biased by tiredness and inattention. Besides, mood during sensory testing may influence results, especially when hurting thresholds are tested [37], Given that pain threshold assessment is conducted using an ascending series, absolute threshold maybe biased by alterations in conclusion making processes. On the other hand psychophysiological testing seemed more appropriate than other methods of measuring sensory processing, because information technology might reverberate the best the subjective experience of the participant. In farther studies a control for melancholia state and tiredness should be included. Moreover, personality traits were assessed via a self-rating-questionnaire. The NEO-FFI is widely used and has proved to take a good reliability and validity [25], but withal processes similar perceived social desirability might play a office in the responses a person provides.

It is as well of import to consider the theoretical background of the personality trait description used in this report. The NEO-FFI is based on the five-factor model of personality [26], [38], which was generated using a lexical arroyo to verbs describing personality. The v-cistron structure was plant to be quite stable and concordant with other models of personality [39], however one of the major critiques of this arroyo is that lexical words might not represent all facets of human personality every bit, simply rather might stand for oversimplified descriptors of man personality. Some other critique of this factor modeling of personality, which is especial important hither, is based around the possibility of a biological footing of such factors. The factors are constructions of relatively stable variables describing personality, just the biological basis for such group has been questioned [40]. One attempt to institute a biological basis for the 'Big five' was attempted by Jang and colleagues. They merits to take plant 2 genetic factors underlying each of the v personality traits [41]. Looking for coherence between personality and sensory capacity with a more than biological basis and a more than detailed personality inventory, might heighten the probability of revealing relationships between genetic inheritance and personality trait.

A significant limitation of this study is the relatively homogeneous sample it used. Participants were young and healthy medical students or members from the Technical University of Dresden. Thus the population was highly educated, high-socioeconomic grouping with petty or no chronic disease or debilitation. Thus, a bias towards college instances and certainly higher valuing of certain personality traits such as enhanced conscientiousness or agreeableness and reduced neuroticism might be predictable. Comparing of the data from these participants with that from a High german normative population sample clearly showed this sample bias. Variation within the expression of traits explored was relatively minor in this sample, again suggesting homogeneity inside it. Every bit correlations normally downsize, when homogeneous samples are analyzed [42], it perchance that the coherence between personality traits and sensory capacity described here augments analyzing a broader spectrum of personality values. Withal it is non possible, at this phase, to generalize these results to a wider population. Future studies should embrace a sample that better represents the wider 'normal' population.

In determination, to our knowledge, this is the first systematic report correlating thresholds in unlike sensory systems and certain personality traits. Nosotros focused on olfactory, gustatory, trigeminal chemosensory and electrical cutaneous thresholds, covering a range of processed environmental cues related to social relationships, eating and detection of potential danger. The study showed coherence between capacities of the olfactory system and agreeableness, possibly moderated through enhanced social perception abilities. Additionally, enhanced sensitivity in the sensory systems detecting danger was constitute to be related to high neuroticism. Information technology could be that the sensitivity with which one is able to perceive environmentally important stimuli influences perception of the environment and is therefore is able to influence development and expression of personality traits.

Acknowledgments

Parts of the results related with this study have been published elsewhere. Delight see: Hummel T, Springborn Grand, Croy I, Lötsch J (2011) Loftier pain sensitivity is singled-out from loftier susceptibility to non-painful sensory input at threshold level. International Journal of Psychophysiology, PMID: 21291919.

Author Contributions

Conceived and designed the experiments: Thursday IC MS JL. Performed the experiments: IC MS. Analyzed the data: IC Thursday. Contributed reagents/materials/analysis tools: Thursday. Wrote the paper: IC Th ANBJ.

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