Meta-analysis of genome-wide association studies for personality.

Personality can be thought of as a set of characteristics that influence people's thoughts, feelings and behavior across a variety of settings. Variation in personality is predictive of many outcomes in life, including mental health. Here we report on a meta-analysis of genome-wide association (GWA) data for personality in 10 discovery samples (17,375 adults) and five in silico replication samples (3294 adults). All participants were of European ancestry. Personality scores for Neuroticism, Extraversion, Openness to Experience, Agreeableness and Conscientiousness were based on the NEO Five-Factor Inventory. Genotype data of ≈ 2.4M single-nucleotide polymorphisms (SNPs; directly typed and imputed using HapMap data) were available. In the discovery samples, classical association analyses were performed under an additive model followed by meta-analysis using the weighted inverse variance method. Results showed genome-wide significance for Openness to Experience near the RASA1 gene on 5q14.3 (rs1477268 and rs2032794, P=2.8 × 10(-8) and 3.1 × 10(-8)) and for Conscientiousness in the brain-expressed KATNAL2 gene on 18q21.1 (rs2576037, P=4.9 × 10(-8)). We further conducted a gene-based test that confirmed the association of KATNAL2 to Conscientiousness. In silico replication did not, however, show significant associations of the top SNPs with Openness and Conscientiousness, although the direction of effect of the KATNAL2 SNP on Conscientiousness was consistent in all replication samples. Larger scale GWA studies and alternative approaches are required for confirmation of KATNAL2 as a novel gene affecting Conscientiousness.

Motion direction identification in random cinematograms: a general model.

The cinematograms of 12 two-state elements arranged in the clock positions in space and in a sequence of adjacent 100-ms frames in time were used as stimuli. Some positions in each frame (or all 12 of them) could be labeled as "domain" ones, and every element that was T frames and S positions (clockwise or counterclockwise) apart from a domain element could repeat the latter's state with probability P. The probability of the rotation direction identification was obtained as a function of T, S, P, number of frames, and the domain positions selection scheme. A generalized version of the reversed phi phenomenon was obtained: if P less than .5, then the psychometric value lies below .5 level. All the data can be accounted for by a simple model according to which the choice of direction is based on the counts of the different types of dipoles, each type being characterized by the probability and the weight of its count: In most situations all dipoles but the shortest ones (connecting the neighboring elements of successive frames) can be ignored.

Competing motion paths in sequence of random dot patterns.

Global motion perception from a sequence of random dot patterns has been studied by means of the competition technique which consists of making a normally less salient motion path in a superimposed multiple-path stimulus more powerful by adding luminous energy to elements forming this path. The perceived motion direction of a sequence of random dot patterns can be dramatically changed by increasing luminance of some fraction of dots leaving all spatial and temporal intervals between dots unchanged. The threshold luminance increment delta I that is required in order to change the perceived motion direction indicates that differently oriented local motion vectors are resolved into a single common motion vector along which the whole pattern appears to move. An inverse spatial proximity rule was discovered: within a certain spatial limit the motion strength of a particular motion path is proportional to the distance between stimulus elements forming this path.

Timing of visual events for motion discrimination.

The observer's task was to identify the temporal order of the two adjacent luminance excursions one of which was a step-function and the other a linear increase in luminance starting from zero and reaching various final amplitude A after some period of time D. The interstimulus delay, delta t, between these two transitions was determined at which they appeared isochronous. The point of the subjective equality (PSE) depended on both ramp parameters, the rise-time duration D and its amplitude A. All of the data can be accounted for by supposing that judgements about the temporal order are based on the comparison of a simple attribute of these luminance excursions, the time moments when the luminous energy concentrated on low temporal frequencies exceeds some level. The perceived temporal order, which was experienced as a leftward or rightward displacement of the whole pattern, was determined by the sequence in which low-frequency portion of these two luminance excursions reached the threshold value. The implications of this simple contrast detection explanation for theories of motion analysis are discussed.

Reaction time to motion onset: local dispersion model analysis.

Data on the simple reaction time to motion onset presented in Ball and Sekuler [Psychol. Rev. 87, 435-469 (1980)] and Tynan and Sekuler [Vision Res. 20, 709-715 (1982)] are re-analysed on the basis of local dispersion model of motion detectability. According to this model the detectability at the moment t is determined by the mean value of the local dispersion function LD (t) within the interval (t-T, t), LD(t) being some measure of scattering (namely, running variance) of spatial positions passed through during the period (t-tau, t). Reaction time is assumed to be equal to the time that takes the detectability to reach some critical level plus constant execution time. Theoretical predictions fit the experimental data perfectly when two main parameters of the model, T/tau and tau are the same as were found appropriate in other, independent experiments on motion detection.

Meta-analysis of genome-wide association studies identifies common variants in CTNNA2 associated with excitement-seeking.

The tendency to seek stimulating activities and intense sensations define excitement-seeking, a personality trait akin to some aspects of sensation-seeking. This trait is a central feature of extraversion and is a component of the multifaceted impulsivity construct. Those who score high on measures of excitement-seeking are more likely to smoke, use other drugs, gamble, drive recklessly, have unsafe/unprotected sex and engage in other risky behaviors of clinical and social relevance. To identify common genetic variants associated with the Excitement-Seeking scale of the Revised NEO Personality Inventory, we performed genome-wide association studies in six samples of European ancestry (N=7860), and combined the results in a meta-analysis. We identified a genome-wide significant association between the Excitement-Seeking scale and rs7600563 (P=2 × 10(-8)). This single-nucleotide polymorphism maps within the catenin cadherin-associated protein, alpha 2 (CTNNA2) gene, which encodes for a brain-expressed α-catenin critical for synaptic contact. The effect of rs7600563 was in the same direction in all six samples, but did not replicate in additional samples (N=5105). The results provide insight into the genetics of excitement-seeking and risk-taking, and are relevant to hyperactivity, substance use, antisocial and bipolar disorders.

The genetic association between personality and major depression or bipolar disorder. A polygenic score analysis using genome-wide association data.

The relationship between major depressive disorder (MDD) and bipolar disorder (BD) remains controversial. Previous research has reported differences and similarities in risk factors for MDD and BD, such as predisposing personality traits. For example, high neuroticism is related to both disorders, whereas openness to experience is specific for BD. This study examined the genetic association between personality and MDD and BD by applying polygenic scores for neuroticism, extraversion, openness to experience, agreeableness and conscientiousness to both disorders. Polygenic scores reflect the weighted sum of multiple single-nucleotide polymorphism alleles associated with the trait for an individual and were based on a meta-analysis of genome-wide association studies for personality traits including 13,835 subjects. Polygenic scores were tested for MDD in the combined Genetic Association Information Network (GAIN-MDD) and MDD2000+ samples (N=8921) and for BD in the combined Systematic Treatment Enhancement Program for Bipolar Disorder and Wellcome Trust Case-Control Consortium samples (N=6329) using logistic regression analyses. At the phenotypic level, personality dimensions were associated with MDD and BD. Polygenic neuroticism scores were significantly positively associated with MDD, whereas polygenic extraversion scores were significantly positively associated with BD. The explained variance of MDD and BD, ∼0.1%, was highly comparable to the variance explained by the polygenic personality scores in the corresponding personality traits themselves (between 0.1 and 0.4%). This indicates that the proportions of variance explained in mood disorders are at the upper limit of what could have been expected. This study suggests shared genetic risk factors for neuroticism and MDD on the one hand and for extraversion and BD on the other.

National character does not reflect mean personality trait levels in 49 cultures.

Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity.

Resolving ambiguities in orientation, motion, and depth domains.

Three different perceptual systems--orientation, motion, and depth--can recover a global perceptual organization from spatially correlated random multielement patterns. In all three cases the global structure composed of random elements is evaluated by mechanisms performing measurements in the energy domain within appropriately defined local space-time areas. The selective increase in energy of one fraction of the elements may dramatically change the whole perceptual organization of the stimulus. In specially devised patterns one and the same element can belong to two or more separate perceptual organizations, the perceptual salience of one of which can be reinforced by a luminance increment of the elements comprising it. If a stimulus provides two different perceptual organizations to which each element could potentially belong, one of four possible solutions of the existing ambiguity will occur: suppression, rivalry, mixture, or parity. Two superimposed global orientation patterns either suppress or dominate over each other but cannot be seen simultaneously or in a mixed form. Characteristic of the depth system is that it allows multiple binocular matchings and parity of possible perceptual solutions. Finally, if a stimulus provides two or more paths along which each element may appear to move, the perceived global motion direction is determined by a mixture of directions of these competing motion paths. Dissimilarities in these ways of resolving ambiguities may be based on different principles defining regularity and coherence of an object in the orientation, motion, and depth domains.

Magnitude of luminance modulation specifies amplitude of perceived movement.

A compelling impression of movement, which is perceptually indistinguishable from a real displacement, can be elicited by patterns containing no spatially displaced elements. An apparent oscillation, w-movement, was generated by a stationary pattern containing a large number of horizontal pairs of spatially adjacent dots modulated in brightness. The observer's task was to adjust the perceived amplitude of the w-motion to match the amplitude of a real oscillation. All of the data can be accounted for by a simple rule: If the relative change in the luminance, W = delta L/L, between two adjacent stationary dots is kept constant, the distance over which these dots appeared to travel in space comprises a fixed fraction of the total distance by which they are separated. The apparent amplitude of the w-motion increases strictly in proportion with luminance contrast, provided that the contrast is represented in the motion-encoding system by a rapidly saturating compressive Weibull transformation. These findings can be explained in terms of bilocal motion encoders comparing two luminance modulations occurring at two different locations.

Contrast response of a movement-encoding system.

The ability to identify the direction of apparent motion in a sequence of two short light pulses of different amplitudes at separate spatial locations was studied. The product of pulse amplitudes is a very poor predictor of such performance when one of the two signals is much higher in amplitude than the other: above a certain amplitude the probability of correct identification becomes virtually independent of the amplitude of the larger pulse. There was no noticeable difference in performance between low-high and high-low contrast sequences. Both the direction identification and the simple contrast-detection probabilities can be represented by the same psychometric function of the luminance increment delta L, provided that delta L is normalized by the nth power of the background luminance level, Lb. These results suggest that the general Reichardt-type scheme of movement encoding should be modified in the manner proposed for the fly's visual system [J. Opt. Soc. Am. A 6, 116 (1989)]: (1) the mean luminance is subtracted from the input signal before the signal is subjected to a nonlinear compression and (2) saturation characteristics are inserted into both branches of the two mirror-symmetric motion-detection subunits before multiplication of the input signals. The identical metric of the contrast response suggests that movement discrimination and luminance detection are two different special-purpose computations performed on the output of the same encoding network.

Occupancy model of perceived numerosity.

Observers saw 234 different pairs of stochastically organized dot patterns and indicated which of the two patterns appeared to be more numerous. All of the data can be accounted for by supposing that the choice of the more numerous pattern is based on the determination of the occupancy indices of both patterns. Each dot is posited to have an impact upon its neighborhood in a constant occupancy radius R. The area of the stimulus plane occupied collectively by all dots provides a basis for judging relative numerosity; the pattern with the larger occupancy value is chosen as more numerous. The occupancy model, besides providing a general explanation of known numerosity illusions in strictly quantitative terms, can explain some puzzling aspects of numerosity perception.

Perceived numerosity of spatiotemporal events.

Numerosity discrimination was examined when items were varied in space-time position rather than in space only. Observers were instructed to indicate which of two adjacent streams of visual events contained more items. The precision of numerosity discrimination of dynamic events was not remarkably different from that of static patterns. Two basic numerosity biases previously found for static dot patterns--inhibitory overestimation and satellite underestimation--were demonstrated for items distributed randomly over a spatiotemporal interval. It was also demonstrated that two streams, equated in the number and luminous energy of items, are not judged equal in their visible number if items in one of these two streams have longer duration than items in the second stream. These findings can be accounted for by the occupancy model of perceived numerosity (Allik & Tuulmets, 1991a) if it is supposed that the impact that each element has on its neighborhood is spread along both spatial and temporal coordinates. Perceived numerosity decreases with both spatial and temporal proximity between the visual items. Space and time have interchangeable effects on perceived numerosity: the amount of numerosity bias caused by the spatial proximity of items can also be produced by the properly chosen temporal proximity of items.

The Estonian Self-Consciousness Scale and its relation to the five-factor model of personality.

The Self-Consciousness Scale (SCS), developed by Fenigstein, Scheier, and Buss (1975), was adapted to the Estonian language. In general, the results supported the 3-factor structure of the SCS. However, many items in the subscales did not load as expected. A 26-item modified scale, the Estonian SCS (ESCS), is presented. A joint factor analysis of the ESCS and the NEO Personality Inventory (NEO-PI) scales led to a 5-factor solution, where all the factors that emerged were identified as the Big Five personality dimensions, the ESCS subscales loading most significantly on 3 of these factors: Neuroticism (N), Extraversion (E), and Openness to Experience (O). Correlation analysis revealed a pattern of correlations, characterized by the strongest associations between Social Anxiety and E (r = -.77), Public Self-Consciousness (PubSC) and N (r = .40), and Private Self-Consciousness (PrivSC) and O (r = .34), which quite well corresponds to the pattern of correlations that was reported for the original versions of the SCS and the NEO-PI (Zuckerman, Kuhlman, Joireman, Teta, & Kraft, 1993). We can conclude that all the SCS subscales can be sufficiently well interpreted in terms of the Big Five model of personality dimensions--PrivSC and PubSC appear to describe some variations of the Big Five themes that are not fully elaborated by the NEO-PI rather than being completely independent domains of individual differences.

Intergration and interruption in the masking of form by form.

Paris of geometric forms of equal area were presented, one form after another, with interstimulus intervals t ranging from 0 to 250 ms. The subject's task in experiment 1 was to recognise both stimuli. Identification of the form presented first (backward masking) across all values of t was of a nonmonotonic nature, with greatest impairment at values of t from 30 to 60 ms. Identification of the second form presented (forward masking) increased monotonically with increasing t. Different forms were recognised with different effectiveness across all values of t where masking took place. The results are interpreted on the basis of a multiple-stage processing model which assumes interaction between stimuli at different levels at different values of t. In experiment 2 the subject's task was to detect the presence or absence of a predesignated form. This condition yielded monotonic functions for both backward and forward masking. An explanation in terms of attention-dependent masking is given.

The fakability of the personal orientation dimensions: evidence for a lie profile.

The resistance of the Personal Orientation Dimensions (POD) to deliberate attempts at creating a favorable impression was investigated. Two groups of college students were used: (a) 21 students completed the POD under standard instructions, then received information about actualization, and completed the POD again under instructions to Create a very good impression; (b) 21 students completed the POD under standard instructions, then received information not related to actualization, and completed the POD again under instructions to create a very good impression. An analyses indicated that providing students with information about actualization did not facilitate their ability to create a favorable impression on the POD. The POD profiles produced by both groups changed significantly, and in a similar direction from pretest to posttest. Evidence is presented suggesting the existence of a "lie profile" which distinguishes deliberate attempts to create a favorable impression on the POD. These findings provide support for the resistance of the POD to deliberate attempts at creating a favorable impression.

Personality and affectivity characteristics associated with eating disorders: a comparison of eating disordered, weight-preoccupied, and normal samples.

The purpose of this study was to assess the relative contribution of personality and emotional experience to self-reported eating attitudes in a group of patients with clinically diagnosed eating disorders, a weight-reduction training group (Weight Watchers), and a control group without body weight problems. Participants in this study (N = 114) completed Estonian versions of the Eating Disorder Inventory-2 (EDI-2; Garner, 1991), NEO Personality Inventory (Costa & McCrae, 1989), and Positive Affect and Negative Affect Schedule, Expanded Form (Watson & Clark, 1994). Data demonstrated validity of the Estonian version of EDI-2 in its ability to identify problems on a continuum of disordered eating behavior. Among the Big Five personality dimensions, Neuroticism made the largest contribution to EDI-2 subscales. Two other dimensions, Openness to Experience and Conscientiousness, also predispose individuals to eating problems. Personality traits made a larger contribution to the self-reported eating pathology than the self-rated effects experienced during the last few weeks. It was argued that personality dispositions have a larger relevancy in the etiology of eating disorders than emotional state.

Control and sense of eye movement behind closed eyelids.

To investigate the question of what happens with regard to position sense and control of the human eyes when the eyelids are closed, the contact-wire-free electromagnetic eye movement recording method was developed. It was shown that after the start of blinking of eyelid closure, the eyeball moves up as the upper eyelids come down. Experimental data show human inability to maintain a given position of the eyes in the head under the closed lids. When the subject was asked to follow a simple geometrical path, a very weak metrical and topological correspondence between desired and actual paths occurred with closed eyes. It is proposed that the poor control of eye movements behind closed eyelids is due to the lack of available information about the eye position in the head. The assumption was confirmed by providing artificial auditory feedback about the eyeball position to the subject, which can be effectively used for gaze stabilization by the subject. It is suggested that visual information is the only useful basis for eye movement regulation under normal conditions.