Positive Affect and Cognitive Restoration: Investigating the Role of Valence and Arousal

Positive moods are thought to restore self-control resources following depletion. However, it is not well understood whether this effect is due to affective valence (pleasantness), arousal (activation), or a combination of both. Across four studies, we set out to investigate the role of positive moods on cognitive and behavioral measures of self-regulation in an ego-depletion paradigm. In studies 1 and 2, we independently manipulated affective valence and arousal and assessed self-regulation with a Stroop task. Results did not suggest a restorative effect of either on cognitive resources. In study 3, we employed both behavioral (the ‘handgrip task’) and cognitive (Stroop) assessments of self-regulation. Again, no significant effect of mood was observed on the Stroop task. Additionally, participants did not persist significantly longer on the handgrip task following a positive mood induction. Finally, in study 4, high vs. low states of arousal were manipulated and self-regulation was assessed via pre- and post-manipulation Stroop performance. In study 4, Stroop performance improved slightly more across time points for those in the high arousal condition than for those in the low arousal condition. Therefore, across four studies, we failed to find a consistent pattern of results suggesting that positive moods restore cognitive resources.     

Simulated heat waves reduce cognitive and motor performance of an endotherm

1. Heat waves cause mass mortality of animals, including humans, across the globe annually, which has drawn new attention to how animals cope with high air temperatures. Recent field research has explored behavioral responses to high air temperatures, which can influence reproductive success and mortality.
2. Less well studied are the effects of high air temperatures on cognition, which may underlie behavioral changes. Specifically, it is poorly known if cognitive declines occur at high temperatures, and if cognitive and motor components of behavior are similarly affected.
3. We tested how well zebra finches (Taeniopygia guttata castanotis), a model for cognition research, performed two learned foraging tasks (color association and detour‐reaching) at mild (22°C) and high (43 and 44°C) air temperatures that occur naturally in their range. We habituated birds to the trial conditions and temperatures on days preceding the test trials and at the trial temperature for 30 min immediately prior to each test trial. Trials lasted less than 10 min. At high air temperatures, zebra finches exhibited heat dissipation behaviors during most tasks, suggesting thermoregulatory challenge.
4. Cognitive performance declined at high air temperatures in two of three measures: Color association was unaffected, but birds missed more food rewards, and did more unproductive behaviors. Motor performance declined at high temperatures on the color association task, including longer times to complete the task, move between food rewards, and process individual seeds. Performance declines varied among components of behavior and among individuals.
5. We combined our behavioral data with existing climate data and predicted that in the austral summer of 2018–2019, zebra finches experienced air temperatures that caused cognitive and motor declines in our captive birds in 34% and 45% of their Australian range, respectively.
6. This study provides novel experimental evidence that high air temperatures cause cognitive and motor performance decline in birds. Further, our results provide insights to how those declines might affect bird ecology and evolution. First, differences in declines among behavioral components may allow identification of behaviors that are most susceptible to decline in the wild. Second, variation in performance declines and heat dissipation behaviors among individuals suggests variability in heat tolerance, which could lead to differential fitness in the wild. Last, these results suggest that high air temperatures cause cognitive declines in the wild and that understanding cognition could help refine predictive models of population persistence.

     

Negative Mood Increases Selective Attention to Negatively Valenced Body Parts in Female Adolescents with Anorexia Nervosa

ObjectivePrevious research has yielded evidence of increased attentional processing of negatively valenced body parts in women with anorexia nervosa (AN), especially for those with high depressive symptomatology. The present study extended previous research by implementing an experimental mood manipulation.MethodIn a within-subjects design, female adolescents with AN (n = 12) and an age matched female control group (CG; n = 12) were given a negative and a positive mood induction at a one-week interval. After each mood induction, participants underwent a 3-min mirror exposure, while their eye movements were recorded.ResultsAfter the positive mood induction, both AN and CG participants displayed longer and more frequent gazes towards their self-defined most ugly relative to their self-defined most beautiful body part. However, after the negative mood induction, only females with AN were characterized by increased attention to their most ugly compared to their most beautiful body part, while CG participants’ attention distribution was balanced. Furthermore, in the negative (but not in the positive) mood induction condition gaze frequency and duration towards the most ugly body part was significantly stronger in the AN group relative to the CG.DiscussionThe results emphasize the role of negative mood in the maintenance of pathological information processing of the self-body. This increased body-related negativity-bias during negative mood may lead to the persistence and aggravation of AN patients’ body image disturbance.     

Attentional Control and Interpretation of Facial Expression after Oxytocin Administration to Typically Developed Male Adults

Deficits in attentional-inhibitory control have been reported to correlate to anger, hostility, and aggressive behavior; therefore, inhibitory control appears to play an important role in prosocial behavior. Moreover, recent studies have demonstrated that oxytocin (OT) exerts a prosocial effect (e.g., decreasing negative behaviors, such as aggression) on humans. However, it is unknown whether the positively valenced effect of OT on sociality is associated with enhanced attentional-inhibitory control. In the present study, we hypothesized that OT enhances attentional-inhibitory control and that the positively valenced effect of OT on social cognition is associated with enhanced attentional-inhibitory control. In a single-blind, placebo-controlled crossover trial, we tested this hypothesis using 20 healthy male volunteers. We considered a decrease in the hostility detection ratio, which reflects the positively valenced interpretation of other individuals’ facial expressions, to be an index of the positively valenced effects of OT (we reused the results of our previously published study). As a measure of attentional-inhibitory control, we employed a modified version of the flanker task (i.e., a shorter conflict duration indicated higher inhibitory control). These results failed to demonstrate any significant behavioral effects of OT (i.e., neither a positively valenced effect on facial cognition nor an effect on attentional-inhibitory control). However, the enhancement of attentional-inhibitory control after OT administration significantly correlated to the positively valenced effects on the interpretation of uncertain facial cognition (i.e., neutral and ambiguous facial expressions).     

Sometimes slower is better: slow-exploring birds are more sensitive to changes in a vocal discrimination task

Animal personality, defined as consistent individual differences across context and time, has attracted much recent research interest in the study of animal behaviour. More recently, this field has begun to examine how such variation arose and is maintained within populations. The habitat-dependent selection hypothesis, which posits that animals with differing personality types may fare better (i.e. have a fitness advantage) in different habitats, suggests one possible mechanism. In the current experiment, we tested whether slow- and fast-exploring black-capped chickadees (Poecile atricapillus), determined by performance in a novel environment exploration task, perform differentially when the demands of an acoustic operant discrimination (cognitive) task were altered following successful task acquisition. We found that slow-exploring birds learn to reverse previously learned natural category rules more quickly than faster exploring conspecifics. In accordance with the habitat-dependent selection hypothesis, and previous work with great tits (Parus major), a close relative of the black-capped chickadee, our results suggest that fast-exploring birds may perform better in stable, predictable environments where forming a routine is advantageous, while slow-exploring birds are favoured in unstable, unpredictable environments, where task demands often change. Our results also support a hypothesis derived from previous work with great tits; slow-exploring birds may be generally more flexible (i.e. able to modify their behaviour in accordance with changes in environmental stimuli) in some learning tasks.     

Unexpected Dual Task Benefits on Cycling in Parkinson Disease and Healthy Adults: A Neuro-Behavioral Model

BackgroundWhen performing two tasks at once, a dual task, performance on one or both tasks typically suffers. People with Parkinson’s disease (PD) usually experience larger dual task decrements on motor tasks than healthy older adults (HOA). Our objective was to investigate the decrements in cycling caused by performing cognitive tasks with a range of difficulty in people with PD and HOAs.MethodsTwenty-eight participants with Parkinson’s disease and 20 healthy older adults completed a baseline cycling task with no secondary tasks and then completed dual task cycling while performing 12 tasks from six cognitive domains representing a wide range of difficulty.ResultsCycling was faster during dual task conditions than at baseline, and was significantly faster for six tasks (all p<.02) across both groups. Cycling speed improved the most during the easiest cognitive tasks, and cognitive performance was largely unaffected. Cycling improvement was predicted by task difficulty (p<.001). People with Parkinson’s disease cycled slower (p<.03) and showed reduced dual task benefits (p<.01) than healthy older adults.ConclusionsUnexpectedly, participants’ motor performance improved during cognitive dual tasks, which cannot be explained in current models of dual task performance. To account for these findings, we propose a model integrating dual task and acute exercise approaches which posits that cognitive arousal during dual tasks increases resources to facilitate motor and cognitive performance, which is subsequently modulated by motor and cognitive task difficulty. This model can explain both the improvement observed on dual tasks in the current study and more typical dual task findings in other studies.     

Do Brain Networks Evolve by Maximizing Their Information Flow Capacity?

We propose a working hypothesis supported by numerical simulations that brain networks evolve based on the principle of the maximization of their internal information flow capacity. We find that synchronous behavior and capacity of information flow of the evolved networks reproduce well the same behaviors observed in the brain dynamical networks of Caenorhabditis elegans and humans, networks of Hindmarsh-Rose neurons with graphs given by these brain networks. We make a strong case to verify our hypothesis by showing that the neural networks with the closest graph distance to the brain networks of Caenorhabditis elegans and humans are the Hindmarsh-Rose neural networks evolved with coupling strengths that maximize information flow capacity. Surprisingly, we find that global neural synchronization levels decrease during brain evolution, reflecting on an underlying global no Hebbian-like evolution process, which is driven by no Hebbian-like learning behaviors for some of the clusters during evolution, and Hebbian-like learning rules for clusters where neurons increase their synchronization.     

Distinct Acute Zones for Visual Stimuli in Different Visual Tasks in Drosophila

The fruit fly Drosophila melanogaster has a sophisticated visual system and exhibits complex visual behaviors. Visual responses, vision processing and higher cognitive processes in Drosophila have been studied extensively. However, little is known about whether the retinal location of visual stimuli can affect fruit fly performance in various visual tasks. We tested the response of wild-type Berlin flies to visual stimuli at several vertical locations. Three paradigms were used in our study: visual operant conditioning, visual object fixation and optomotor response. We observed an acute zone for visual feature memorization in the upper visual field when visual patterns were presented with a black background. However, when a white background was used, the acute zone was in the lower visual field. Similar to visual feature memorization, the best locations for visual object fixation and optomotor response to a single moving stripe were in the lower visual field with a white background and the upper visual field with a black background. The preferred location for the optomotor response to moving gratings was around the equator of the visual field. Our results suggest that different visual processing pathways are involved in different visual tasks and that there is a certain degree of overlap between the pathways for visual feature memorization, visual object fixation and optomotor response.     

Detecting Cheaters without Thinking: Testing the Automaticity of the Cheater Detection Module

Evolutionary psychologists have suggested that our brain is composed of evolved mechanisms. One extensively studied mechanism is the cheater detection module. This module would make people very good at detecting cheaters in a social exchange. A vast amount of research has illustrated performance facilitation on social contract selection tasks. This facilitation is attributed to the alleged automatic and isolated operation of the module (i.e., independent of general cognitive capacity). This study, using the selection task, tested the critical automaticity assumption in three experiments. Experiments 1 and 2 established that performance on social contract versions did not depend on cognitive capacity or age. Experiment 3 showed that experimentally burdening cognitive resources with a secondary task had no impact on performance on the social contract version. However, in all experiments, performance on a non-social contract version did depend on available cognitive capacity. Overall, findings validate the automatic and effortless nature of social exchange reasoning.     

Patterned-String Tasks: Relation between Fine Motor Skills and Visual-Spatial Abilities in Parrots

String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla) and the cockatiel (Nymphicus hollandicus), forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.     

Androgens with activity at estrogen receptor beta have anxiolytic and cognitive-enhancing effects in male rats and mice

Testosterone (T) and its metabolites may underlie some beneficial effects for anxiety and cognition, but the mechanisms for these effects are unclear. T is reduced to dihydrotestosterone (DHT), which can be converted to 5α-androstane,3α,17β-diol (3α-diol) and/or 5α-androstane-3β,17β-diol (3β-diol). Additionally, T can be converted to androstenedione, and then to androsterone. These metabolites bind with varying affinity to androgen receptors (ARs; T and DHT), estrogen receptors (ERβ; 3α-diol, 3β-diol), or GABA_A/benzodiazepine receptors (GBRs; 3α-diol, androsterone). Three experiments were performed to investigate the hypothesis that reduced anxiety-like and enhanced cognitive performance may be due in part to actions of T metabolites at ERβ. Experiment 1: Gonadectomized (GDX) wildtype and ERβ knockout mice (βERKO) were subcutaneously (SC) administered 3α-diol, 3β-diol, androsterone, or oil vehicle at weekly intervals, and tested in anxiety tasks (open field, elevated plus maze, light–dark transition) or for cognitive performance in the object recognition task. Experiment 2: GDX rats were administered SC 3α-diol, 3β-diol, androsterone, or oil vehicle, and tested in the same tasks. Experiment 3: GDX rats were androsterone- or vehicle-primed and administered an antagonist of ARs (flutamide), ERs (tamoxifen), or GBRs (flumazenil), or vehicle and then tested in the elevated plus maze. Both rats and wildtype mice, but not βERKO mice, consistently had reduced anxiety and improved performance in the object recognition task. Androsterone was only effective at reducing anxiety-like behavior in the elevated plus maze and this effect was modestly reduced by flumazenil administration. Thus, actions at ERβ may be required for T's anxiety-reducing and cognitive-enhancing effects.     

Spouses and cats and their effects on human mood

Abstract

Previous data indicated that cats influence the moods of singly living people only by decreasing negative moods, while not affecting positive moods. In this study, we asked if such an effect can be 1) replicated, 2) is comparable to the effect of a human partner, and 3) related to the owner's attachment towards the cat. Two hundred and twelve couples with cats, 31 couples without cats, singly living people with cats (47 women, 45 men) and singly living people without cats (43 women, 9 men) volunteered to participate. We used a list of adjectives (the “EWL”-Questionnaire) to assess their mood, which they responded to on an evening of their choice. The Lexington Attachment to Pets Scale (LAPS) was additionally completed by the cat owners. Selected adjectives were reduced by factor analyses and labeled bad mood, activity, good mood, and seclusion, according to the highest loadings of mood items within each factor. Each mood factor was explained by cat ownership, presence or absence of a partner, and the person's sex. Further, sex, partner status and attachment towards cats explained moods amongst the cat owners. Only the partner, but not the cat, enhanced positive moods. Cats alleviated negative moods, and this effect was comparable to the effect of a human partner. This compensatory effect of cat ownership on negative moods was not comparable to a similar effect of degree of attachment towards the cat on human mood. Possible reasons for the unidirectional effect of cats on human mood are discussed.     

Singly Living People and Their Cats: A Study of Human Mood and Subsequent Behavior

ABSTRACT

We sought to examine how cat owners' moods correlated with subsequent interactions with their cats. Such a relationship has not been previously documented. Data from 47 women and 49 men living alone with their cats were collected. Participants were visited at their homes for one two-hour session each. Approximately five minutes before and after the observation period, the owners filled out a standard questionnaire (EWL, list of adjectives) to indicate their current mood. The EWL allowed the authors to later assign owner moods to one or more of 14 sub-scales. In this study, results on correlates of moods at the beginning and during the subsequent first half hour of interactions are presented. Multiple regression analyses showed that related mood sub-scales, e.g. anxiety and depressiveness, can influence human behavior in different directions, and that bipolar mood sub-scales, e.g. introvertedness and extrovertedness, do not necessarily work in opposite directions. Four human behaviors were related to mood: intents to interact, starts of interactions, and approaches and vocalizations while interacting. While the start of an interaction was influenced by eight different mood sub-scales, the others mentioned were only related to four sub-scales at most. The only recorded behavior of the cat that was significantly correlated with the owner's mood was approaches to the owner within an ongoing interaction.     

General Intelligence in Another Primate: Individual Differences across Cognitive Task Performance in a New World Monkey (Saguinus oedipus)

Background

Individual differences in human cognitive abilities show consistently positive correlations across diverse domains, providing the basis for the trait of “general intelligence” (g). At present, little is known about the evolution of g, in part because most comparative studies focus on rodents or on differences across higher-level taxa. What is needed, therefore, are experiments targeting nonhuman primates, focusing on individual differences within a single species, using a broad battery of tasks. To this end, we administered a large battery of tasks, representing a broad range of cognitive domains, to a population of captive cotton-top tamarin monkeys (Saguinus oedipus).

Methodology and Results

Using a Bayesian latent variable model, we show that the pattern of correlations among tasks is consistent with the existence of a general factor accounting for a small but significant proportion of the variance in each task (the lower bounds of 95% Bayesian credibility intervals for correlations between g and task performance all exceed 0.12).

Conclusion

Individual differences in cognitive abilities within at least one other primate species can be characterized by a general intelligence factor, supporting the hypothesis that important aspects of human cognitive function most likely evolved from ancient neural substrates.     

Light affects behavioral despair involving the clock gene Period 1

Light at night has strong effects on physiology and behavior of mammals. It affects mood in humans, which is exploited as light therapy, and has been shown to reset the circadian clock in the suprachiasmatic nuclei (SCN). This resetting is paramount to align physiological and biochemical timing to the environmental light-dark cycle. Here we provide evidence that light at zeitgeber time (ZT) 22 affects mood-related behaviors also in mice by activating the clock gene Period1 (Per1) in the lateral habenula (LHb), a brain region known to modulate mood-related behaviors. We show that complete deletion of Per1 in mice led to depressive-like behavior and loss of the beneficial effects of light on this behavior. In contrast, specific deletion of Per1 in the region of the LHb did not affect mood-related behavior, but suppressed the beneficial effects of light. RNA sequence analysis in the mesolimbic dopaminergic system revealed profound changes of gene expression after a light pulse at ZT22. In the nucleus accumbens (NAc), sensory perception of smell and G-protein coupled receptor signaling were affected the most. Interestingly, most of these genes were not affected in Per1 knock-out animals, indicating that induction of Per1 by light serves as a filter for light-mediated gene expression in the brain. Taken together we show that light affects mood-related behavior in mice at least in part via induction of Per1 in the LHb with consequences on mood-related behavior and signaling mechanisms in the mesolimbic dopaminergic system.     

Dynamical aspects of behavior generation under constraints

Dynamic adaptation is a key feature of brains helping to maintain the quality of their performance in the face of increasingly difficult constraints. How to achieve high-quality performance under demanding real-time conditions is an important question in the study of cognitive behaviors. Animals and humans are embedded in and constrained by their environments. Our goal is to improve the understanding of the dynamics of the interacting brain–environment system by studying human behaviors when completing constrained tasks and by modeling the observed behavior. In this article we present results of experiments with humans performing tasks on the computer under variable time and resource constraints. We compare various models of behavior generation in order to describe the observed human performance. Finally we speculate on mechanisms how chaotic neurodynamics can contribute to the generation of flexible human behaviors under constraints.     

Lithium treatment alleviates impaired cognition in a mouse model of fragile X syndrome

Fragile X syndrome (FXS) is caused by suppressed expression of fragile X mental retardation protein (FMRP), which results in intellectual disability accompanied by many variably manifested characteristics, such as hyperactivity, seizures and autistic‐like behaviors. Treatment of mice that lack FMRP, Fmr1 knockout (KO) mice, with lithium has been reported to ameliorate locomotor hyperactivity, prevent hypersensitivity to audiogenic seizures, improve passive avoidance behavior and attenuate sociability deficits. To focus on the defining characteristic of FXS, which is cognitive impairment, we tested if lithium treatment ameliorated impairments in four cognitive tasks in Fmr1 KO mice, tested if the response to lithium differed in adolescent and adult mice and tested if therapeutic effects persisted after discontinuation of lithium administration. Fmr1 KO mice displayed impaired cognition in the novel object detection task, temporal ordering for objects task and coordinate and categorical spatial processing tasks. Chronic lithium treatment of adolescent (from 4 to 8 weeks of age) and adult (from 8 to 12 weeks of age) mice abolished cognitive impairments in all four cognitive tasks. Cognitive deficits returned after lithium treatment was discontinued for 4 weeks. These results show that Fmr1 KO mice exhibit severe impairments in these cognitive tasks, that lithium is equally effective in normalizing cognition in these tasks whether it is administered to young or adult mice and that lithium administration must be continued for the cognitive improvements to be sustained. These findings provide further evidence that lithium administration may be beneficial for individuals with FXS .     

Combining oxytocin administration and positive emotion inductions: Examining social perception and analytical performance

Intranasal administration of the hypothalamic neuropeptide oxytocin (OT) has, in some studies, been associated with positive effects on social perception and cognition. Similarly, positive emotion inductions can improve a range of perceptual and performance-based behaviors. In this exploratory study, we examined how OT administration and positive emotion inductions interact in their associations with social and analytical performance. Participants (N = 124) were randomly assigned to receive an intranasal spray of OT (40 IU) or placebo and then viewed one of three videos designed to engender one of the following emotion states: social warmth, pride, or an affectively neutral state. Following the emotion induction, participants completed social perception and analytical tasks. There were no significant main effects of OT condition on social perception tasks, failing to replicate prior research, or on analytical performance. Further, OT condition and positive emotion inductions did not interact with each other in their associations with social perception performance. However, OT condition and positive emotion manipulations did significantly interact in their associations with analytical performance. Specifically, combining positive emotion inductions with OT administration was associated with worse analytical performance, with the pride induction no longer benefiting performance and the warmth induction resulting in worse performance. In sum, we found little evidence for main or interactive effects of OT on social perception but preliminary evidence that OT administration may impair analytical performance when paired with positive emotion inductions.     

Cognitive Reflection and the Diligent Worker: An Experimental Study of Millennials

Recent studies have shown that despite crucially needing the creative talent of millennials (people born after 1980) organizations have been reluctant to hire young workers because of their supposed lack of diligence. We propose to help resolve this dilemma by studying the determinants of task performance and shirking behaviors of millennials in a laboratory work environment. We find that cognitive ability is a good predictor of task performance in line with previous literature. In contrast with previous research, personality traits do not consistently predict either task performance or shirking behaviors. Shirking behaviors, as measured by the time participants spent browsing the internet for non-work purposes (Cyberloafing), were only explained by the performance on the Cognitive Reflection Test (CRT). This finding echoes recent research in cognitive psychology according to which conventional measures of cognitive ability only assess a narrow concept of rational thinking (the algorithmic mind) that fails to capture individuals’ capacity to reflect and control their impulses. Our findings suggest that hiring diligent millennials relies on the use of novel cognitive measures such as CRT in lieu of standard personality and intelligence tests.     

Association of Brain-Derived Neurotrophic Factor Gene Val66Met Polymorphism with Primary Dysmenorrhea

Primary dysmenorrhea (PDM), the most prevalent menstrual cycle-related problem in women of reproductive age, is associated with negative moods. Whether the menstrual pain and negative moods have a genetic basis remains unknown. Brain-derived neurotrophic factor (BDNF) plays a key role in the production of central sensitization and contributes to chronic pain conditions. BDNF has also been implicated in stress-related mood disorders. We screened and genotyped the BDNF Val66Met polymorphism (rs6265) in 99 Taiwanese (Asian) PDMs (20–30 years old) and 101 age-matched healthy female controls. We found that there was a significantly higher frequency of the Met allele of the BDNF Val66Met polymorphism in the PDM group. Furthermore, BDNF Met/Met homozygosity had a significantly stronger association with PDM compared with Val carrier status. Subsequent behavioral/hormonal assessments of sub-groups (PDMs = 78, controls = 81; eligible for longitudinal multimodal neuroimaging battery studies) revealed that the BDNF Met/Met homozygous PDMs exhibited a higher menstrual pain score (sensory dimension) and a more anxious mood than the Val carrier PDMs during the menstrual phase. Although preliminary, our study suggests that the BDNF Val66Met polymorphism is associated with PDM in Taiwanese (Asian) people, and BDNF Met/Met homozygosity may be associated with an increased risk of PDM. Our data also suggest the BDNF Val66Met polymorphism as a possible regulator of menstrual pain and pain-related emotions in PDM. Absence of thermal hypersensitivity may connote an ethnic attribution. The presentation of our findings calls for further genetic and neuroscientific investigations of PDM.