A review of assessment methods for measuring individual differences in oral somatosensory perception.

While taste and smell perception have been thoroughly investigated, our understanding of oral somatosensory perception remains limited. Further, assessing and measuring individual differences in oral somatosensory perception pose notable challenges. This review aimed to evaluate the existing methods to assess oral somatosensory perception by examining and comparing the strengths and limitations of each method. The review highlighted the lack of standardized assessment methods and the various procedures within each method. Tactile sensitivity can be assessed using several methods, but each method measures different tactile dimensions. Further investigations are needed to confirm its correlation with texture sensitivity. In addition, measuring a single textural attribute may not provide an overall representation of texture sensitivity. Thermal sensitivity can be evaluated using thermal-change detection or temperature discrimination tests. The chemesthetic sensitivity tests involve either localized or whole-mouth stimulation tests. The choice of an appropriate method for assessing oral somatosensory sensitivity depends on several factors, including the specific research objectives and the target population. Each method has its unique intended purpose, strengths, and limitations, so no universally superior approach exists. To overcome some of the limitations associated with certain methods, the review offers alternative or complementary approaches that could be considered. Researchers can enhance the comprehensive assessment of oral somatosensory sensitivity by carefully selecting and potentially combining methods. In addition, a standardized protocol remains necessary for each method.

The role of environmental sensitivity in the experience and processing of emotions: implications for well-being.

Several theories suggest that people differ significantly in their environmental sensitivity, defined as the capacity to perceive and process information about the environment. More sensitive people, who make up between 25% and 30% of the population, are not only more negatively affected by adverse experiences but also benefit disproportionately from positive ones, in line with differential susceptibility theory. Heightened emotional reactivity has been identified as one of the key markers of sensitivity. However, the current understanding of the relationship between sensitivity and the experience and processing of emotions remains limited. In the current paper we propose a new conceptual framework for the multiple ways in which environmental sensitivity may impact on different aspects of the experience and processing of emotions. This includes heightened perception of emotions, increased emotional reactivity, as well as the important role of emotion regulation for the well-being of highly sensitive people. In addition, we also consider rearing experiences in shaping sensitivity and emotion regulation. The reviewed empirical studies largely support the conceptual model but more research is needed to explore the dynamics between sensitivity and emotions further. Finally, we discuss several implications for well-being before making a case for the inclusion of individual differences in environmental sensitivity in affective science. This article is part of the theme issue 'Sensing and feeling: an integrative approach to sensory processing and emotional experience'.

Sea anemones (Actinia equina) show consistent individual differences in boldness and thoroughness but lack a behavioural syndrome.

Behavioural syndromes are suites of behaviours that corelate between-individuals but the same behaviours may also show within-individual correlations owing to state dependency or trade-offs. Therefore, overall phenotypic behavioural correlations must be separated into their between- and within-individual components. We investigate how startle response duration (an index of boldness) and time taken to reject an inert item (an index of investigation thoroughness) covary in beadlet sea anemones, Actinia equina. Anemones took longer to reject a more complex item compared to a simpler one, validating this measure of investigation thoroughness. We then quantified between- and within-individual correlations using a Bayesian analysis and an alternative frequentist analysis, which returned the same results. Startle responses decreased with anemone size while thoroughness decreased across repeated observations, indicative of simple learning. For each behaviour, repeatability was significant but relatively low and there was no behavioural syndrome. Rather, the two behaviours showed a negative within-individual correlation in most individuals. Thus, boldness and thoroughness are unlikely to be under correlative selection, and they may instead be expressed independently, in line with the general pattern that cross-contextual behavioural syndromes are comparatively rare. It now appears that this pattern may extend broadly across animal diversity.

Wild raccoons demonstrate flexibility and individuality in innovative problem-solving.

Cognitive skills, such as innovative problem-solving, are hypothesized to aid animals in urban environments. However, the significance of innovation in wild populations, and its expression across individuals and socio-ecological conditions, is poorly understood. To identify how and when innovation arises in urban-dwelling species, we used advanced technologies and new testing and analytical methods to evaluate innovative problem-solving abilities of wild raccoons (Procyon lotor). We deployed multi-compartment puzzle boxes with either one or multiple solution types and identified raccoons using radio frequency identification. Raccoons solved these novel extractive foraging tasks, and their success was influenced by age and exploratory diversity. Successful raccoons always discovered multiple different solution types, highlighting flexible problem-solving. Using a unique, comparative sequence analysis approach, we found that variation in raccoon solving techniques was greater between individuals than within individuals, and this self-similarity intensified during times of competition. Finally, the inclusion of an easier solution in the multi-solution trials enabled previously unsuccessful raccoons to bootstrap their learning and successfully open multiple difficult solutions. Our study suggests that innovative problem-solving is probably influenced by many factors and has provided novel field and analytical methods, as well as new insights on the socio-ecological dynamics of urban populations.

Natural clues to danger: attachment behavior in threatening situations.

A fundamental principle of attachment theory is that threatening situations give rise to individual differences in the extent to which people seek proximity to close others. The current research examines the way in which attachment styles predict individual differences in attachment-relevant behavior during threatening events. We tested alternative theoretical perspectives concerning the association between adult attachment (specifically, attachment avoidance) and attachment behavior in the presence of natural clues to danger by observing couples (N = 204) when they were watching horror vs. control film excerpts. Results suggest that highly avoidant people engaged in less attachment behavior across both threatening and non-threatening situations. These findings have implications for the understanding of attachment-related processes and how working models of the self and others facilitate (or inhibit) the expression of attachment behavior.

Attachment and inter-individual differences in empathy, compassion, and theory of mind abilities.

Social processing, namely the ability to understand others' cognitive and affective states, is crucial for successful social interaction. It encompasses socio-affective abilities such as empathy and compassion, as well as socio-cognitive abilities such as theory of mind (ToM). This study examined the link between social processing and attachment. Our study goes beyond previous research in that social processing abilities were assessed in a single, state-of-the-art behavioral paradigm using video narratives, the EmpaToM. Attachment was captured with the Adult Attachment Interview (N = 85; 50.60% women, Mage = 25.87 ± 4.50 years) measuring participants' present-day capacity to think about and communicate attachment-relevant information about the past. Additionally, a self-report attachment questionnaire was employed (N = 158). We found that AAI-based attachment security (vs. insecurity) was associated with higher behavioral ToM abilities. Furthermore, self-reported attachment avoidance was negatively correlated with behavioral compassion abilities. Our findings provide further evidence that interview-based and self-reported attachment measures do not converge, but may rather be understood as capturing different facets of attachment that relate to different components of social processing. We conclude that individuals with secure, non-avoidant attachment show social abilities that allow them to better understand others' thoughts and generate positive, caring emotions in face of others' distress.

Attachment is differentially associated with distinct behavioral social processing abilities, that is, compassion and theory of mind.Higher attachment security in the Adult Attachment Interview (AAI) is linked to higher behavioral theory of mind abilities.Increased self-reported attachment avoidance is linked to lower behavioral compassion.

Inter-individual variability in neural response to low doses of LSD.

The repeated use of small doses of psychedelics (also referred to as "microdosing") to facilitate benefits in mental health, cognition, and mood is a trending practice. Placebo-controlled studies however have largely failed to demonstrate strong benefits, possibly because of large inter-individual response variability. The current study tested the hypothesis that effects of low doses of LSD on arousal, attention and memory depend on an individual's cognitive state at baseline. Healthy participants (N = 53) were randomly assigned to receive repeated doses of LSD (15 mcg) or placebo on 4 occasions divided over 2 weeks. Each treatment condition also consisted of a baseline and a 1-week follow-up visit. Neurophysiological measures of arousal (resting state EEG), pre-attentive processing (auditory oddball task), and perceptual learning and memory (visual long-term potentiation (LTP) paradigm) were assessed at baseline, dosing session 1 and 4, and follow-up. LSD produced stimulatory effects as reflected by a reduction in resting state EEG delta, theta, and alpha power, and enhanced pre-attentive processing during the acute dosing sessions. LSD also blunted the induction of LTP on dosing session 4. Stimulatory effects of LSD were strongest in individuals with low arousal and attention at baseline, while inhibitory effects were strongest in high memory performers at baseline. Decrements in delta EEG power and enhanced pre-attentive processing in the LSD treatment condition were still present during the 1-week follow-up. The current study demonstrates across three cognitive domains, that acute responses to low doses of LSD depend on the baseline state and provides some support for LSD induced neuroadaptations that sustain beyond treatment.

Minocycline Abrogates Individual Differences in Nerve Injury-Evoked Affective Disturbances in Male Rats and Prevents Associated Supraspinal Neuroinflammation.

Chronic neuropathic pain precipitates a complex range of affective and behavioural disturbances that differ markedly between individuals. While the reasons for differences in pain-related disability are not well understood, supraspinal neuroimmune interactions are implicated. Minocycline has antidepressant effects in humans and attenuates affective disturbances in rodent models of pain, and acts by reducing neuroinflammation in both the spinal cord and brain. Previous studies, however, tend not to investigate how minocycline modulates individual affective responses to nerve injury, or rely on non-naturalistic behavioural paradigms that fail to capture the complexity of rodent behaviour. We investigated the development and resolution of pain-related affective disturbances in nerve-injured male rats by measuring multiple spontaneous ethological endpoints on a longitudinal naturalistic foraging paradigm, and the effect of chronic oral minocycline administration on these changes. Disrupted foraging behaviours appeared in 22% of nerve-injured rats - termed 'affected' rats - and were present at day 14 but partially resolved by day 21 post-injury. Minocycline completely prevented the emergence of an affected subgroup while only partly attenuating mechanical allodynia, dissociating the relationship between pain and affect. This was associated with a lasting downregulation of ΔFosB expression in ventral hippocampal neurons at day 21 post-injury. Markers of microglia-mediated neuroinflammation were not present by day 21, however proinflammatory microglial polarisation was apparent in the medial prefrontal cortex of affected rats and not in CCI minocycline rats. Individual differences in affective disturbances following nerve injury are therefore temporally related to altered microglial morphology and hippocampal neuronal activation, and are abrogated by minocycline.

Unpredictable benefits of social information can lead to the evolution of individual differences in social learning.

Human ecological success is often attributed to our capacity for social learning, which facilitates the spread of adaptive behaviours through populations. All humans rely on social learning to acquire culture, but there is substantial variation across societies, between individuals and over developmental time. However, it is unclear why these differences exist. Here, we present an evolutionary model showing that individual variation in social learning can emerge if the benefits of social learning are unpredictable. Unpredictability selects for flexible developmental programmes that allow individuals to update their reliance on social learning based on previous experiences. This developmental flexibility, in turn, causes some individuals in a population to end up consistently relying more heavily on social learning than others. We demonstrate this core evolutionary mechanism across three scenarios of increasing complexity, investigating the impact of different sources of uncertainty about the usefulness of social learning. Our results show how evolution can shape how individuals learn to learn from others, with potentially profound effects on cultural diversity.

Short-Term Memory Capacity Predicts Willingness to Expend Cognitive Effort for Reward.

We must often decide whether the effort required for a task is worth the reward. Past rodent work suggests that willingness to deploy cognitive effort can be driven by individual differences in perceived reward value, depression, or chronic stress. However, many factors driving cognitive effort deployment-such as short-term memory ability-cannot easily be captured in rodents. Furthermore, we do not fully understand how individual differences in short-term memory ability, depression, chronic stress, and reward anticipation impact cognitive effort deployment for reward. Here, we examined whether these factors predict cognitive effort deployment for higher reward in an online visual short-term memory task. Undergraduate participants were grouped into high and low effort groups (n HighEffort = 348, n LowEffort = 81; n Female = 332, n Male = 92, M Age = 20.37, Range Age = 16-42) based on decisions in this task. After completing a monetary incentive task to measure reward anticipation, participants completed short-term memory task trials where they could choose to encode either fewer (low effort/reward) or more (high effort/reward) squares before reporting whether or not the color of a target square matched the square previously in that location. We found that only greater short-term memory ability predicted whether participants chose a much higher proportion of high versus low effort trials. Drift diffusion modeling showed that high effort group participants were more biased than low effort group participants toward selecting high effort trials. Our findings highlight the role of individual differences in cognitive effort ability in explaining cognitive effort deployment choices.

Individual differences in sharing false political information on social media: Deliberate and accidental sharing, motivations and positive schizotypy.

False political information-misinformation or disinformation-is widely spread on social media. Individual social media users play a large part in this. However, only a minority actively share false material. It is important to establish what sets these individuals apart from those who do not, and why they do it. Motivations for sharing may vary and are likely to differ between people who share false material unknowingly and on purpose. In this paper we consider the extent to which individual differences in personality and other variables, and motivations for sharing, are associated with the likelihood of people sharing false political information both accidentally and deliberately. In a series of four studies (Ns = 614, 563, 627, 113) we examined predictors of sharing false political information using different methodological approaches. Across the four studies, a key finding was that positive schizotypy is associated with measures of sharing false information both accidentally and deliberately. Motivations for sharing political information online were also relevant, with sharing for reasons of 'raising awareness' appearing particularly important. Implications for research and practice are discussed.

Individual differences in the boldness of female zebrafish are associated with alterations in serotonin function.

One of the most prevalent axes of behavioral variation in both humans and animals is risk taking, where individuals that are more willing to take risk are characterized as bold while those that are more reserved are regarded as shy. Brain monoamines (i.e. serotonin, dopamine and noradrenaline) have been found to play a role in a variety of behaviors related to risk taking. Using zebrafish, we investigated whether there was a relationship between monoamine function and boldness behavior during exploration of a novel tank. We found a correlation between serotonin metabolism (5-HIAA:5-HT ratio) and boldness during the initial exposure to the tank in female animals. The DOPAC:DA ratio correlated with boldness behavior on the third day in male fish. There was no relationship between boldness and noradrenaline. To probe differences in serotonergic function in bold and shy fish, we administered a selective serotonin reuptake inhibitor, escitalopram, and assessed exploratory behavior. We found that escitalopram had opposing effects on thigmotaxis in bold and shy female animals: the drug caused bold fish to spend more time near the center of the tank and shy fish spent more time near the periphery. Taken together, our findings indicate that variation in serotonergic function has sex-specific contributions to individual differences in risk-taking behavior.

Network and state specificity in connectivity-based predictions of individual behavior.

Predicting individual behavior from brain functional connectivity (FC) patterns can contribute to our understanding of human brain functioning. This may apply in particular if predictions are based on features derived from circumscribed, a priori defined functional networks, which improves interpretability. Furthermore, some evidence suggests that task-based FC data may yield more successful predictions of behavior than resting-state FC data. Here, we comprehensively examined to what extent the correspondence of functional network priors and task states with behavioral target domains influences the predictability of individual performance in cognitive, social, and affective tasks. To this end, we used data from the Human Connectome Project for large-scale out-of-sample predictions of individual abilities in working memory (WM), theory-of-mind cognition (SOCIAL), and emotion processing (EMO) from FC of corresponding and non-corresponding states (WM/SOCIAL/EMO/resting-state) and networks (WM/SOCIAL/EMO/whole-brain connectome). Using root mean squared error and coefficient of determination to evaluate model fit revealed that predictive performance was rather poor overall. Predictions from whole-brain FC were slightly better than those from FC in task-specific networks, and a slight benefit of predictions based on FC from task versus resting state was observed for performance in the WM domain. Beyond that, we did not find any significant effects of a correspondence of network, task state, and performance domains. Together, these results suggest that multivariate FC patterns during both task and resting states contain rather little information on individual performance levels, calling for a reconsideration of how the brain mediates individual differences in mental abilities.

Approaching lifelong learning: An integrated framework for explaining decision-making processes in personal and professional development.

BACKGROUND: Individual differences in commitment to lifelong learning, a process aimed at seizing opportunities for self-development, have not been extensively studied. OBJECTIVE: Our aim is to provide a comprehensive understanding of the decision-making mechanisms involved in pursuing learning for self-development. METHOD: We conducted a literature review on the taxing nature of cognitive exertion and its impact on the inclination to engage in cognitively demanding tasks for learning, as well as individual differences in sensitivity to aversive or rewarding outcomes inherent in the learning process. RESULTS: Our findings indicate that the Expected Value of Control (EVC) theory can elucidate the former, while research on approach-avoidance motivation can shed light on the latter. CONCLUSION: We propose and develop an integrated framework that incorporates both lines of research. This framework holds relevance for neuropsychology, experimental psychology, and education psychology, offering theoretical guidance for tailoring learning experiences to enhance engagement and commitment to self-development.

Large Individual Differences in Functional Connectivity in the Context of Major Depression and Antidepressant Pharmacotherapy.

Clinical studies of major depression (MD) generally focus on group effects, yet interindividual differences in brain function are increasingly recognized as important and may even impact effect sizes related to group effects. Here, we examine the magnitude of individual differences in relation to group differences that are commonly investigated (e.g., related to MD diagnosis and treatment response). Functional MRI data from 107 participants (63 female, 44 male) were collected at baseline, 2, and 8 weeks during which patients received pharmacotherapy (escitalopram, N = 68) and controls (N = 39) received no intervention. The unique contributions of different sources of variation were examined by calculating how much variance in functional connectivity was shared across all participants and sessions, within/across groups (patients vs controls, responders vs nonresponders, female vs male participants), recording sessions, and individuals. Individual differences and common connectivity across groups, sessions, and participants contributed most to the explained variance (>95% across analyses). Group differences related to MD diagnosis, treatment response, and biological sex made significant but small contributions (0.3-1.2%). High individual variation was present in cognitive control and attention areas, while low individual variation characterized primary sensorimotor regions. Group differences were much smaller than individual differences in the context of MD and its treatment. These results could be linked to the variable findings and difficulty translating research on MD to clinical practice. Future research should examine brain features with low and high individual variation in relation to psychiatric symptoms and treatment trajectories to explore the clinical relevance of the individual differences identified here.

Individual differences in working memory impact the trajectory of non-native speech category learning.

What is the role of working memory over the course of non-native speech category learning? Prior work has predominantly focused on how working memory might influence learning assessed at a single timepoint. Here, we substantially extend this prior work by examining the role of working memory on speech learning performance over time (i.e., over several months) and leverage a multifaceted approach that provides key insights into how working memory influences learning accuracy, maintenance of knowledge over time, generalization ability, and decision processes. We found that the role of working memory in non-native speech learning depends on the timepoint of learning and whether individuals learned the categories at all. Among learners, across all stages of learning, working memory was associated with higher accuracy as well as faster and slightly more cautious decision making. Further, while learners and non-learners did not have substantially different working memory performance, learners had faster evidence accumulation and more cautious decision thresholds throughout all sessions. Working memory may enhance learning by facilitating rapid category acquisition in initial stages and enabling faster and slightly more careful decision-making strategies that may reduce the overall effort needed to learn. Our results have important implications for developing interventions to improve learning in naturalistic language contexts.

How material sensory properties and individual differences influence the haptic aesthetic appeal of visually presented stimuli.

Touch plays a crucial role for humans. Despite its centrality in sensory experiences, the field of haptic aesthetics is underexplored. So far, existing research has revealed that preferences in the haptic domain are related to stimulus properties and the Gestalt laws of grouping. Additionally, haptic aesthetics is influenced by top-down processes, e.g., stimulus familiarity, and is likely to be modulated by personality and expertise. To further our understanding of these influences on haptic aesthetic appraisal, the current study investigated the imagined haptic aesthetic appeal of visually presented material surfaces, considering the role of haptic expertise, Need for touch, personality traits. The results revealed a positive influence of familiarity, simplicity, smoothness, warmth, lightness, dryness, slipperiness and a negative influence of complexity on individuals' aesthetic responses. While the study failed to support the predicted influence of Need for touch and haptic expertise on aesthetic responses, results did reveal an influence of openness to experience, conscientiousness and neuroticism. Despite the limitations related to the indirect stimuli presentation (vision only), the findings contribute to the relatively unexplored role of bottom-up and top-down features in haptic aesthetics that might be incorporated into the design of consumers' products to better meet their preferences.

New measures of number line estimation performance reveal children's ordinal understanding of numbers.

Children's performance on the number line estimation task, often measured by the percentage of absolute error, predicts their later mathematics achievement. This task may also reveal (a) children's ordinal understanding of the target numbers in relation to each other and the benchmarks (e.g., endpoints, midpoint) and (b) the ordinal skills that are a necessary precursor to children's ability to understand the interval nature of a number line as measured by percentage of absolute error. Using data from 104 U.S. kindergartners, we measured whether children's estimates were correctly sequenced across trials and correctly positioned relative to given benchmarks within trials at two time points. For both time points, we found that each ordinal error measure revealed a distinct pattern of data distribution, providing opportunities to tap into different aspects of children's ordinal understanding. Furthermore, children who made fewer ordinal errors scored higher on the Test of Early Mathematics Ability and showed greater improvement on their interval understanding of numbers as reflected by a larger reduction of percentage of absolute error from Time 1 to Time 2. The findings suggest that our number line measures reveal individual differences in children's ordinal understanding of numbers, and that such understanding may be a precursor to their interval understanding and later mathematics performance.

Individual differences in face salience and rapid face saccades.

Humans saccade to faces in their periphery faster than to other types of objects. Previous research has highlighted the potential importance of the upper face region in this phenomenon, but it remains unclear whether this is driven by the eye region. Similarly, it remains unclear whether such rapid saccades are exclusive to faces or generalize to other semantically salient stimuli. Furthermore, it is unknown whether individuals differ in their face-specific saccadic reaction times and, if so, whether such differences could be linked to differences in face fixations during free viewing. To explore these open questions, we invited 77 participants to perform a saccadic choice task in which we contrasted faces as well as other salient objects, particularly isolated face features and text, with cars. Additionally, participants freely viewed 700 images of complex natural scenes in a separate session, which allowed us to determine the individual proportion of first fixations falling on faces. For the saccadic choice task, we found advantages for all categories of interest over cars. However, this effect was most pronounced for images of full faces. Full faces also elicited faster saccades compared with eyes, showing that isolated eye regions are not sufficient to elicit face-like responses. Additionally, we found consistent individual differences in saccadic reaction times toward faces that weakly correlated with face salience during free viewing. Our results suggest a link between semantic salience and rapid detection, but underscore the unique status of faces. Further research is needed to resolve the mechanisms underlying rapid face saccades.

Mindreading quality versus quantity: A theoretically and empirically motivated two-factor structure for individual differences in adults' mindreading.

Existing methods for studying individual differences in adults' mindreading often lack good psychometric characteristics. Moreover, it remains unclear, even in theory, how mindreading varies in adults who already possess an understanding of mental states. In this pre-registered study, it was hypothesised that adults vary in their motivation for mindreading and in the degree to which their answers on mindreading tasks are appropriate (context-sensitive). These factors are confounded in existing measures as they do not differentiate between the frequency of mental state terms (MST), indicative of motivation, and the quality of an explanation. Using an innovative scoring system, the current study examined whether individual differences in adult undergraduate psychology students' (N = 128) answer quality and / or quantity of explicit references to others' mental states on two open-ended response mindreading tasks were separable constructs, accounted for by mindreading motivation, and related differentially to measures previously linked with mindreading (e.g., religiosity, loneliness, social network size). A two-factor and one-factor model both provided acceptable fit. Neither model showed significant associations with mindreading motivation. However, a two-factor model (with MST and response appropriateness loading onto separate factors) provided greater explanatory power. Specifically, MST was positively associated with religiosity and response appropriateness was negatively associated with religiosity, whilst the one-factor solution did not predict any socially relevant outcomes. This provides some indication that mindreading quantity and mindreading quality may be distinguishable constructs in the structure of individual differences in mindreading.