Substantial Individual Differences Research Articles

Learning Towards Transportation Network Equilibrium: A Model Comparison Study

As an interdisciplinary topic, human travel-choice behavior has attracted the interests of transportation managers, theoretical computer science researchers and economists. Recent studies on tacit coordination in iterated route choice games (i.e., a large number of subjects could achieve the transportation network equilibrium in limited rounds) have been driven by two questions. (1) Will learning behavior promote tacit coordination in route choice games? (2) Which learning model can best account for these choices/behaviors? To answer the first question, we choose a set of learning models and conduct extensive simulations to determine their success in accounting for major behavioral patterns. To answer the second question, we compare these models to one another by competitively testing their predictions on four different datasets. Although all the selected models account reasonably well for the slow convergence of the mean route choice to equilibrium, they account only moderately well for the mean frequencies of the round-to-round switches from one route to another and fail to appropriately account for substantial individual differences. The implications of these findings for model construction and testing are briefly discussed.

Age-Related Declines in Occipital GABA are Associated with Reduced Fluid Processing Ability

Healthy aging is associated with pervasive declines in cognitive, motor, and sensory functioning. There are, however, substantial individual differences in behavioral performance among older adults. Several lines of animal research link age-related reductions of gamma-aminobutyric acid (GABA), the brain's primary inhibitory neurotransmitter, to age-related cognitive, motor, and sensory decline. Our study used proton magnetic resonance spectroscopy (MRS) at 3T to explore whether occipital GABA declines with age in humans and whether individual differences in occipital GABA are linked to individual differences in fluid processing ability. We used a MEGA-PRESS sequence that combines frequency spectral editing with a point-resolved spectroscopy sequence to quantify GABA. Spectra were obtained from a 30 × 30 × 25 mm voxel placed in the occipital cortex of 20 young adults (mean age 20.7 years) and 18 older adults (mean age 76.5 years). Participants also performed 11 fluid processing tasks outside the scanner, the results of which were z-scored and averaged to calculate a summary measure of fluid processing ability. Regression analysis was employed to determine the relationship between GABA concentrations in the occipital cortex and a summary measure of fluid processing ability. Occipital GABA was significantly lower in older participants compared to the younger participants. We also observed a significant positive relationship between occipital GABA and fluid processing ability. In fact, higher GABA was associated with better task performance in 10 of the 11 tasks. These findings suggest that GABA levels decline with age in humans and are associated with declines in fluid processing ability.

Individual Differences in Risk Perception of Artificial Intelligence

Abstract. This cross-sectional study (N = 325) investigated the relationship between the Dark Triad personality traits and the perception of artificial intelligence (AI) risk. Narrow AI risk perception was measured based on recently identified perceived risks in the public. Artificial general intelligence (AGI) risk perception was operationalized in terms of plausibility ratings and subjective probability estimates on deceptive AI scenarios developed by Bostrom (2014) , in which AI-sided deception is described as a function of intelligence. Machiavellianism and psychopathy predicted narrow AI risk perception above the shared variance of the Dark Triad and above the Big Five. In individuals with self-reported knowledge of machine learning, the Dark Triad traits were associated with AGI risk perception. This study provides evidence for the existence of substantial individual differences in the risk perception of AI.

Reliable individual differences in fine-grained cortical functional architecture

Fine-grained functional organization of cortex is not well-conserved across individuals. As a result, individual differences in cortical functional architecture are confounded by topographic idiosyncrasies—i.e., differences in functional–anatomical correspondence. In this study, we used hyperalignment to align information encoded in topographically variable patterns to study individual differences in fine-grained cortical functional architecture in a common representational space. We characterized the structure of individual differences using three common functional indices, and assessed the reliability of this structure across independent samples of data in a natural vision paradigm. Hyperalignment markedly improved the reliability of individual differences across all three indices by resolving topographic idiosyncrasies and accommodating information encoded in spatially fine-grained response patterns. Our results demonstrate that substantial individual differences in cortical functional architecture exist at fine spatial scales, but are inaccessible with anatomical normalization alone.

Environmental drivers of harbour porpoise fine-scale movements

Quantifying intraspecific variation in movement behaviour of marine predators and the underlying environmental drivers is important to inform conservation management of protected species. Here, we provide the first empirical data on fine-scale movements of free-ranging harbour porpoises (Phocoena phocoena) in their natural habitat. Data were obtained from six individuals, tagged in two areas of the Danish North Sea, that were equipped with Global Positioning System (GPS) and dive recorder units (V-tags). We used multi-model inference and model averaging to evaluate the relative importance of various static and dynamic environmental conditions on the movement characteristics: speed, turning angle, dive duration, dive depth, dive wiggliness (a proxy for prey chasing behaviour), and post-dive duration. Despite substantial individual differences in horizontal and vertical movement patterns, we found that all the tracked porpoises responded similar to variation in environmental conditions and displayed movements that indicate a higher likelihood of foraging behaviour in shallower and more saline waters. Our study contributes to the identification of important feeding areas for porpoises and can be used to improve existing movement-based simulation models that aim to assess the impact of anthropogenic disturbance on harbour porpoise populations.

Dynamic cognitive models of intertemporal choice

Traditionally, descriptive accounts of intertemporal choice have relied on static and deterministic models that assume alternative-wise processing of the options. Recent research, by contrast, has highlighted the dynamic and probabilistic nature of intertemporal choice and provided support for attribute-wise processing. Currently, dynamic models of intertemporal choice—which account for both the resulting choice and the time course over which the construction of a choice develops—rely exclusively on the framework of evidence accumulation. In this article, we develop and rigorously compare several candidate schemes for dynamic models of intertemporal choice. Specifically, we consider an existing dynamic modeling scheme based on decision field theory and develop two novel modeling schemes—one assuming lexicographic, noncompensatory processing, and the other built on the classical concepts of random utility in economics and discrimination thresholds in psychophysics. We show that all three modeling schemes can accommodate key behavioral regularities in intertemporal choice. When empirical choice and response time data were fit simultaneously, the models built on random utility and discrimination thresholds performed best. The results also indicated substantial individual differences in the dynamics underlying intertemporal choice. Finally, model recovery analyses demonstrated the benefits of including both choice and response time data for more accurate model selection on the individual level. The present work shows how the classical concept of random utility can be extended to incorporate response dynamics in intertemporal choice. Moreover, the results suggest that this approach offers a successful alternative to the dominating evidence accumulation approach when modeling the dynamics of decision making.

Individual differences in compliance and agreement for sleep logs and wrist actigraphy: A longitudinal study of naturalistic sleep in healthy adults.

There is extensive laboratory research studying the effects of acute sleep deprivation on biological and cognitive functions, yet much less is known about naturalistic patterns of sleep loss and the potential impact on daily or weekly functioning of an individual. Longitudinal studies are needed to advance our understanding of relationships between naturalistic sleep and fluctuations in human health and performance, but it is first necessary to understand the efficacy of current tools for long-term sleep monitoring. The present study used wrist actigraphy and sleep log diaries to obtain daily measurements of sleep from 30 healthy adults for up to 16 consecutive weeks. We used non-parametric Bland-Altman analysis and correlation coefficients to calculate agreement between subjectively and objectively measured variables including sleep onset time, sleep offset time, sleep onset latency, number of awakenings, the amount of wake time after sleep onset, and total sleep time. We also examined compliance data on the submission of daily sleep logs according to the experimental protocol. Overall, we found strong agreement for sleep onset and sleep offset times, but relatively poor agreement for variables related to wakefulness including sleep onset latency, awakenings, and wake after sleep onset. Compliance tended to decrease significantly over time according to a linear function, but there were substantial individual differences in overall compliance rates. There were also individual differences in agreement that could be explained, in part, by differences in compliance. Individuals who were consistently more compliant over time also tended to show the best agreement and lower scores on behavioral avoidance scale (BIS). Our results provide evidence for convergent validity in measuring sleep onset and sleep offset with wrist actigraphy and sleep logs, and we conclude by proposing an analysis method to mitigate the impact of non-compliance and measurement errors when the two methods provide discrepant estimates.

Spontaneous focusing on numerosity in preschool as a predictor of mathematical skills and knowledge in the fifth grade

Previous studies in a variety of countries have shown that there are substantial individual differences in children’s spontaneous focusing on numerosity (SFON), and these differences are positively related to the development of early numerical skills in preschool and primary school. A total of 74 5-year-olds participated in a 7-year follow-up study, in which we explored whether SFON measured with very small numerosities at 5 years of age predicts mathematical skills and knowledge, math motivation, and reading in fifth grade at 11 years of age. Results show that preschool SFON is a unique predictor of arithmetic fluency and number line estimation but not of rational number knowledge, mathematical achievement, math motivation, or reading. These results hold even after taking into account age, IQ, working memory, digit naming, and cardinality skills. The results of the current study further the understanding of how preschool SFON tendency plays a role in the development of different formal mathematical skills over an extended period of time.

Evaluation of Tobramycin Exposure Predictions in Three Bayesian Forecasting Programmes Compared with Current Clinical Practice in Children and Adults with Cystic Fibrosis.

Bayesian forecasting (BF) methods for tobramycin dose individualisation has not seen widespread clinical adoption, despite being endorsed by clinical practice guidelines. Several freeware and commercial programmes using BF methods are available to support personalised dosing. This study evaluated exposure estimates, dose recommendations, and predictive performance compared with current clinical practice. Data from 105 patients (50 adults and 55 children) with cystic fibrosis who received intravenous tobramycin treatment and had paired concentration-time measurements were analysed using (1) log-linear regression analysis, and (2) three BF programmes: TDMx, InsightRX, and DoseMe. Exposure estimates and dose recommendations were compared using the Wilcoxon signed-rank test and Bland-Altman analysis. Predictive performance of BF programmes was compared based on bias and imprecision. Median estimated tobramycin exposure with current clinical practice was significantly lower (87.8 vs. 92.5, 94.0 and 90.3mg h l-1; p≤0.01), hence median subsequent dose recommendations were significantly higher (10.1 vs. 9.4, 9.4 and 9.2mgkg-1; p≤0.01) compared with BF programmes. Furthermore, median relative dose-adjustment differences were higher in adults (>10%) compared with children (4.4-7.8%), and differences in individual dose recommendations were >20% on 19.1-27.4% of occasions. BF programmes showed low bias (<7%) and imprecision (<20%), and none of the programmes made consistently significantly different recommendations compared with each other. On average, the predictions made by the BF programmes were similar, however substantial individual differences were observed for some patients. This suggests the need for detailed investigations of true tobramycin exposure.

Cross-task and cross-manipulation stability in shifting the decision criterion

ABSTRACTIn recognition memory experiments participants must discriminate between old and new items, a judgment influenced by response bias. Research has shown substantial individual differences in the extent to which people will strategically adjust their response bias to diagnostic cues such as the prior probability of an old item. Despite this significant between subject variability, shifts in bias have been found to be relatively predictive within individuals across memory tests. Experiment 1 sought to determine whether this predictability extends beyond memory. Results revealed that the amount a subject shifted response bias in a recognition memory task was significantly predictive of shifting in a visual perception task, suggesting that shifting can generalise outside of a specific testing domain. Experiment 2 sought to determine how predictive shifting would be across two manipulations well known to induce shifts in bias: a probability manipulation and a response payoff manipulation. A modest positive relationship between these two methods was observed, suggesting that shifting behaviour is relatively predictive across different manipulations of shifting. Overall, results from both experiments suggest that response bias shifting, like response bias setting, is a relatively stable behaviour within individuals despite changes in test domain and test manipulation.

Identity exploration and commitment in early adolescence: Genetic and environmental contributions.

Identity formation is a key developmental task in adolescence. Although many adolescents in modern societies face issues of identity, there are substantial individual differences in identity exploration and commitment. Little is known about the origins of these individual differences. The current study investigated the genetic and environmental contributions to identity formation. In total, 571 11-year-old twins (85 monozygotic complete pairs and 176 dizygotic complete pairs) reported on their identity formation, using the Dimensions of Identity Development Scale (DIDS; Luyckx, Schwartz, Berzonsky, et al., 2008), as part of the Longitudinal Israeli Study of Twins (LIST; Avinun & Knafo, 2013). Multidimensional scaling analysis and confirmatory factor analysis supported the presence of all 5 dimensions at this young age: commitment making, exploration in-breadth, ruminative exploration, identification with commitment, and exploration in-depth. However, a model where exploration in-depth was divided into two subscales had a better fit to the data. Monozygotic twins were more similar to each other than dizygotic twins on all dimensions, except for one of the exploration in-depth subscales, supporting the idea that individual differences in various dimensions of identity formation are at least partially influenced by genetics (18-45%). For these dimensions, the rest of the variance was explained by nonshared environment effects (55-82%). Only one of the exploration in-depth subscales, that is, the tendency to explore commitments through discussion with others, showed evidence for the influence of the environment shared by twins (21%) but no genetic effect. Implications of the findings regarding the role of genetics and environment to identity formation are discussed. (PsycINFO Database Record

Individual differences in perceptual adaptation to phonetic categories: Categorization gradiency and cognitive abilities

We examine whether listeners flexibly adapt to unfamiliar speech patterns such as those encountered in foreign-accented English vowels. In these cases, the relative informativity of acoustic dimensions (spectral quality vs. duration) can be changed such that the most informative dimension (spectral quality) is no longer informative, but the role of the secondary cue (duration) is enhanced. We further test whether listeners’ adaptive strategies are related to individual differences in utilizations of secondary cues (measured by categorization gradiency) and cognitive abilities. Native English listeners (N = 36) listened to continuum of vowels /ɛ/ and /æ/ (as in head and had) varying spectral and duration values to complete a perceptual adaptation task, a visual analogue scaling (VAS) task, and were given cognitive ability tasks examining executive function capacities. Results showed that listeners mostly used spectral quality to signal vowel category at baseline, but rapidly adapted by up-weighting reliance on duration when spectral quality was no longer informative. The VAS task showed substantial individual differences in categorization gradiency with more gradient listeners using a secondary cue more, but gradiency was not linked to degree of adaptation. Finally, results of cognitive ability tasks revealed that individual differences in inhibitory control, but not the other cognitive abilities, correlated with the amount of perceptual adaptation.

Big Five personality stability, change, and codevelopment across adolescence and early adulthood.

Using data from 2 large and overlapping cohorts of Dutch adolescents, containing up to 7 waves of longitudinal data each (N = 2,230), the present study examined Big Five personality trait stability, change, and codevelopment in friendship and sibling dyads from age 12 to 22. Four findings stand out. First, the 1-year rank-order stability of personality traits was already substantial at age 12, increased strongly from early through middle adolescence, and remained rather stable during late adolescence and early adulthood. Second, we found linear mean-level increases in girls' conscientiousness, in both genders' agreeableness, and in boys' openness. We also found temporal dips (i.e., U-shaped mean-level change) in boys' conscientiousness and in girls' emotional stability and extraversion. We did not find a mean-level change in boys' emotional stability and extraversion, and we found an increase followed by a decrease in girls' openness. Third, adolescents showed substantial individual differences in the degree and direction of personality trait changes, especially with respect to conscientiousness, extraversion, and emotional stability. Fourth, we found no evidence for personality trait convergence, for correlated change, or for time-lagged partner effects in dyadic friendship and sibling relationships. This lack of evidence for dyadic codevelopment suggests that adolescent friends and siblings tend to change independently from each other and that their shared experiences do not have uniform influences on their personality traits. (PsycINFO Database Record

Hidden Markov model analysis reveals the advantage of analytic eye movement patterns in face recognition across cultures

It remains controversial whether culture modulates eye movement behavior in face recognition. Inconsistent results have been reported regarding whether cultural differences in eye movement patterns exist, whether these differences affect recognition performance, and whether participants use similar eye movement patterns when viewing faces from different ethnicities. These inconsistencies may be due to substantial individual differences in eye movement patterns within a cultural group. Here we addressed this issue by conducting individual-level eye movement data analysis using hidden Markov models (HMMs). Each individual’s eye movements were modeled with an HMM. We clustered the individual HMMs according to their similarities and discovered three common patterns in both Asian and Caucasian participants: holistic (looking mostly at the face center), left-eye-biased analytic (looking mostly at the two individual eyes in addition to the face center with a slight bias to the left eye), and right-eye-based analytic (looking mostly at the right eye in addition to the face center). The frequency of participants adopting the three patterns did not differ significantly between Asians and Caucasians, suggesting little modulation from culture. Significantly more participants (75%) showed similar eye movement patterns when viewing own- and other-race faces than different patterns. Most importantly, participants with left-eye-biased analytic patterns performed significantly better than those using either holistic or right-eye-biased analytic patterns. These results suggest that active retrieval of facial feature information through an analytic eye movement pattern may be optimal for face recognition regardless of culture.

A Novel Method for Assessing Muscle Power During the Standing Cable Wood Chop Exercise.

Zemková, E, Cepková, A, Uvaček, M, and Šooš, L. A novel method for assessing muscle power during the standing cable wood chop exercise. J Strength Cond Res 31(8): 2246-2254, 2017-The study estimates the repeatability and sensitivity of a novel method for assessing (a) the maximal power during the standing cable wood chop exercise with different weights and (b) the endurance of the core muscles. A group of 23 fit men performed (a) maximal effort single repetitions of the standing cable wood chop exercise with weights increasing stepwise up to 1 repetition maximum (1RM) and (b) a set of 20 repetitions at a previously established weight at which maximal power was achieved. Results showed that mean power during the standing cable wood chop exercise is a reliable parameter, with intraclass correlation coefficient values above 0.90 for all weights tested. It was also shown to be a sensitive parameter able to discriminate within-group differences in the maximal power and endurance of core muscles. Substantial individual differences were found in mean power, especially at higher weights, and in the maximal power achieved at about 75% of 1RM (462.2 ± 57.4 W, n = 11), 67% of 1RM (327.2 ± 49.7 W, n = 7), and 83% of 1RM (524.0 ± 63.2 W, n = 5). At these weights, there were also significant differences between the initial and the final repetitions of the wood chop exercise (13.9%, p = 0.025; 10.2%, p = 0.036; and 13.8%, p = 0.028, respectively). These findings indicate that evaluation of the maximal power and endurance of the core muscles during the standing cable wood chop exercise on a weight stack machine is a reliable method and sensitive to differences among physically active individuals.

Error consciousness predicts physiological response to an acute psychosocial stressor in men

There are substantial individual differences in the response towards acute stressor. The aim of the current study was to examine how the neural activity after an error response during a non-stressful state, prospectively predicts the magnitude of physiological stress response (e.g., cortisol response and heart rate) and negative affect elicited by a laboratory stress induction procedure in nonclinical participants. Thirty-seven healthy young male adults came to the laboratory for the baseline neurocognitive measurement on the first day during which they performed a Go/Nogo task with their electroencephalogram recorded. On the second day, they came again to be tested on their stress response using an acute psychosocial stress procedure (i.e., the Trier Social Stress Test, the TSST). Results showed that the amplitude of error positivity (Pe) significantly predicted both the heart rate and cortisol response towards the TSST. Our results suggested that baseline cognitive neural activity reflecting error consciousness could be used as a biological predictor of physiological response to an acute psychological stressor in men.

Culture moderates changes in linguistic self-presentation and detail provision when deceiving others.

Change in our language when deceiving is attributable to differences in the affective and cognitive experience of lying compared to truth telling, yet these experiences are also subject to substantial individual differences. On the basis of previous evidence of cultural differences in self-construal and remembering, we predicted and found evidence for cultural differences in the extent to which truths and lies contained self (versus other) references and perceptual (versus social) details. Participants (N = 320) of Black African, South Asian, White European and White British ethnicity completed a catch-the-liar task in which they provided genuine and fabricated statements about either their past experiences or an opinion and counter-opinion. Across the four groups we observed a trend for using more/fewer first-person pronouns and fewer/more third-person pronouns when lying, and a trend for including more/fewer perceptual details and fewer/more social details when lying. Contrary to predicted cultural differences in emotion expression, all participants showed more positive affect and less negative affect when lying. Our findings show that liars deceive in ways that are congruent with their cultural values and norms, and that this may result in opposing changes in behaviour.

Trainability in lexical specificity mediates between short-term memory and both vocabulary and rhyme awareness

A major goal in the early years of elementary school is learning to read, a process in which children show substantial individual differences. To shed light on the underlying processes of early literacy, this study investigates the interrelations among four known precursors to literacy: phonological short-term memory, vocabulary size, rhyme awareness, and trainability in the phonological specificity of lexical representations, by means of structural equation modelling, in a group of 101 4-year-old children. Trainability in lexical specificity was assessed by teaching children pairs of new phonologically-similar words. Standardized tests of receptive vocabulary, short-term memory, and rhyme awareness were used. The best-fitting model showed that trainability in lexical specificity partially mediated between short-term memory and both vocabulary size and rhyme awareness. These results demonstrate that individual differences in the ability to learn phonologically-similar new words are related to individual differences in vocabulary size and rhyme awareness.

Correlation of NK Cell Phenotypic Properties with Individual Differences in Human Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

Abstract Antibody-dependent cell-mediated cytotoxicity (ADCC) supports anti-viral protection and monoclonal antibody anti-tumor therapies. We used two assays to compare ADCC of healthy donors: CX@1:1 (the percentage cells killed at a 1:1 ratio of CD16Apositive NK cells to ‘target’ cells that were pre-labeled with saturating antibody); and EC50 (the effective concentration of antibody that supports 50% of maximal ADCC). CX@1:1 measures lytic capacity while the EC50 measures cellular recognition; there was no correlation between the 2 assays though we observed 4.5-fold differences among donors in each assay. We correlated ADCC with 5 cytometric parameters (the median fluorescent intensities [MFIs] of the CD16A IgG Fc-receptor; the %NK cells positive &amp; MFIs of the adhesion molecule CD2; the MFIs of perforin; and the %CD16Apositive of CD56positive NK cells) and with CD16A V&amp;F genotypes that affect FcR affinity. For CX@1:1, the best donor killed 73% of targets while the worst killed 16% and perforin levels correlated weakly (P=0.11). Unexpectedly and inexplicably, the %CD16Apositive cells among NK cells correlated (P&amp;lt;0.05). CD16A and CD2 were dissociated from CX@1:1 as might be expected for the high antibody concentrations. For EC50s, there were no statistical correlations except for the expected difference between V/V &amp;V/F vs. F/F genotypes, though the P=0.11. We conclude that substantial individual differences in ADCC per CD16Apositive NK cell are determined by parameters other than cell surface receptors and perforin. The unanticipated correlation of %CD16Apositive NK cells with CX@1:1 has potential as a surrogate marker for ADCC function.

Individual differences in fear extinction and anxiety-like behavior

There is growing appreciation for the substantial individual differences in the acquisition and inhibition of aversive associations, and the insights this might give into identifying individuals particularly vulnerable to stress and psychopathology. We examined whether animals that differed in rate of extinction (i.e., Fast versus Slow) were different in their response to an acute stress in adulthood or following a chronic stress that occurred either early or later in life. We found that Slow Extinguishers had significantly poorer extinction retention than Fast Extinguishers, but an acute stressor did not differentially affect anxiety-like behavior in the two groups. Further, while exposure to chronic stress in adulthood did not impact on the extinction phenotypes or anxiety-like behavior, exposure to chronic stress early in life affected both extinction retention and anxiety-like behavior. These findings have implications for the development of a more nuanced approach to identifying those most at risk of anxiety disorders.