The Italian version of Edinburgh Handedness Inventory: Translation, transcultural adaptation, and validation in healthy subjects

Lateralization is a key aspect of brain architecture and handedness is its primary manifestation. The Edinburgh Handedness Inventory (EHI) and the laterality quotient (LQ) assess the direction and consistency of handedness and require translation and cross-cultural adaptation to guarantee construct validity. We developed a standardized Italian EHI version. The developed Italian version was tested on 202 Italian subjects, classified into three hand types based on their LQs: right, mixed, and left. The frequency of left-handedness in Italians and other populations was compared to previous data. LQs from the twenty- and the ten-item original inventories were also compared. We conducted a factorial analysis. Mcdonald's Omega tested internal consistency. The prevalence of left-handedness was 6.4%, consistent with prior findings in Italian samples and other EHI translations. Age was the only socio-demographic variable that significantly affected the LQ. The internal consistency of the Italian EHI was excellent. Handedness is a feature of several cognitive functions and some neuropsychological diseases; it is influenced by socio-demographic and cultural factors and the instrument used to assess it. To provide a consistent and comparable evaluation of the construct, we recommend using this validated Italian translation of the EHI.

Both direction and degree of handedness as influential factors in rumination

There is contradictory evidence on the influence of handedness on depression and anxiety. However, few studies have investigated the relationship between handedness and rumination, which is robustly associated with both depression and anxiety. This study aimed to examine the influence of direction and consistency of handedness on rumination, considering four different classifications of handedness. The study sample included 406 participants (282 females) who attended an online survey and answered a demographic questionnaire, the Edinburgh Handedness Inventory, the Ruminative Response Scale, and the second edition of the Beck Depression Inventory. Considering four different classifications of handedness, a series of one-way ANOVAs was conducted to investigate any differences between the handedness groups. Besides, linear regression models were used to predict depression or rumination scores among the whole study sample, left-handers, and right-handers. Consistency of handedness predicted rumination among right-handers (but not left-handers), with a direct association between consistency and brooding/total rumination scores. Also, consistent left-handers and consistent right-handers showed higher brooding scores than inconsistent right-handers. Overall, the results supported the significant influence of both direction and consistency of handedness on individual differences in rumination and suggested consistent- and left-handedness as perpetuating factors for ruminative response style.

A comparison of different established and novel methods to determine horses' laterality and their relation to rein tension

The present study aimed to assess an agreement between established and novel methods to determine laterality and to identify the distribution of laterality in warmbloods and Thoroughbreds. Nine different methods to investigate a horses' laterality outside a riding context and during riding were compared across two groups of horses (sample A: 67 warmblood- type horses, sample B: 61 Thoroughbreds). Agreement between any two methods was assessed by calculating Cohen's kappa with McNemar's test or Bowker's Test of Symmetry, and the deviation from equal distributions was assessed with chi²-tests. Continuous variables such as rein tension parameters were analyzed using ANOVA or linear mixed models. Generally, laterality test results obtained outside a riding context did not agree with laterality during riding or among each other (Bonferroni corrected p > 0.0018). However, the rider's assessment of her/his horse's laterality allowed conclusions on rein tension symmetry (p = 0.003), and it also agreed substantially with the lateral displacement of the hindquarters (p = 0.0003), a method that was newly developed in the present study. The majority of warmbloods had their hindquarters displaced to the right (73.1%, X² = 14.3; p < 0.0001). The pattern of lateral displacement of the hindquarters was similar in the Thoroughbred sample (right: 60.7%, left: 39.3%), but did not deviate significantly from an equal distribution (X² = 2.8; p > 0.05). Laterality seems to be manifested in different ways, which generally are not related to each other. Attention should be paid to the desired information when selecting methods for the assessment of laterality. Horses' laterality has an impact on the magnitude and symmetry of rein tension. Matching horses and riders according to their laterality might be beneficial for the stability of rein tension and thus improve training.

The Handedness Index Practical Task (HI20): An economic behavioural measure for assessing manual preference

ABSTRACTBecause self-report hand preference measures are limited to investigating cognitive aspects of manual laterality, valid, easy-to-administer and economic behavioural methods are needed for capturing the motoric component of handedness. Therefore, this study introduces the Handedness Index Practical Task (HI₂₀) and tests it in a sample of 206 students (M_age = 23.79 years, SD_age = 3.01 years), half of whom were self-specified left-handers. After confirming good reliabilities at the subscale and total scale levels, k-means cluster analysis allowed an empirically based partitioning of test subjects into left- (n = 72), mixed- (n = 23) and right-handers (n = 111). To validate this categorization and the HI₂₀ index, data were compared with the Edinburgh Handedness Inventory (EHI), EHI-short, HI₂₂ and hand grip strength. The congruency between the HI₂₀ clusters and alternative categorizations ranged from 95.6% to 84.0%, while the clusters explained large portions of variance in grip strength differences. The HI₂₀ sub- and total scores showed strong correlations with other measures of lateral preference. Altogether, the freely available HI₂₀ emerges as a reliable and valid alternative for behavioural handedness assessment, whose power lies in explaining differential hand use patterns and enabling fine-grained examinations of handedness.

Handedness Development: A Model for Investigating the Development of Hemispheric Specialization and Interhemispheric Coordination

The author presents his perspective on the character of science, development, and handedness and relates these to his investigations of the early development of handedness. After presenting some ideas on what hemispheric specialization of function might mean for neural processing and how handedness should be assessed, the neuroscience of control of the arms/hands and interhemispheric communication and coordination are examined for how developmental processes can affect these mechanisms. The author’s work on the development of early handedness is reviewed and placed within a context of cascading events in which different forms of handedness emerge from earlier forms but not in a deterministic manner. This approach supports a continuous rather than categorical distribution of handedness and accounts for the predominance of right-handedness while maintaining a minority of left-handedness. Finally, the relation of the development of handedness to the development of several language and cognitive skills is examined.

Dimensions over categories: a meta-analysis of taxometric research

Taxometric procedures have been used extensively to investigate whether individual differences in personality and psychopathology are latently dimensional or categorical ('taxonic'). We report the first meta-analysis of taxometric research, examining 317 findings drawn from 183 articles that employed an index of the comparative fit of observed data to dimensional and taxonic data simulations. Findings supporting dimensional models outnumbered those supporting taxonic models five to one. There were systematic differences among 17 construct domains in support for the two models, but psychopathology was no more likely to generate taxonic findings than normal variation (i.e. individual differences in personality, response styles, gender, and sexuality). No content domain showed aggregate support for the taxonic model. Six variables - alcohol use disorder, intermittent explosive disorder, problem gambling, autism, suicide risk, and pedophilia - emerged as the most plausible taxon candidates based on a preponderance of independently replicated findings. We also compared the 317 meta-analyzed findings to 185 additional taxometric findings from 96 articles that did not employ the comparative fit index. Studies that used the index were 4.88 times more likely to generate dimensional findings than those that did not after controlling for construct domain, implying that many taxonic findings obtained before the popularization of simulation-based techniques are spurious. The meta-analytic findings support the conclusion that the great majority of psychological differences between people are latently continuous, and that psychopathology is no exception.

No Evidence That Lateral Preferences Predict Individual Differences in the Tendency to Update Mental Representations: A Replication-Extension Study

A growing body of evidence suggests that inconsistent hand preference is indicative of an increased disposition to update one’s beliefs upon exposure to novel information. This is attributed to a facilitated exchange of information between the two brain hemispheres among inconsistent handers, compared to consistent handers. Currently available studies provide only indirect evidence for such an effect, were mostly based on small sample sizes, and did not provide measures of effect size. Small sample size is a major factor contributing to low replicability of research findings and false-positive results. We thus attempted to replicate Experiment 1 of Westfall, Corser and Jasper (2014), which appears to be representative of research on degree of handedness and belief updating in terms of the employed methods. We utilized data from a sample more than 10 times the size (N = 1243) of the original study and contrasted the commonly applied median-split technique to classify inconsistent and consistent handers with an empirically grounded classification scheme. Following a replication-extension approach, besides handedness, footedness was also explored. Only one out of 12 chi-squared tests reached significance and supported the original hypothesis that inconsistent handers stay with, or switch more often from, the status quo than consistent handers, depending on the valence of novel information. A small-telescopes analysis suggested that the original study had too low analytic power to detect its reported effect reliably. These results cast doubt on the assumption that inconsistent and consistent-handers differ in the tendency to update mental representations. We discuss the use of the median-split technique in handedness research, available neuroscientific evidence on interhemispheric interaction and inconsistent handedness, and venues of future research.

Wait wait, don't tell me: Handedness questionnaires do not predict hand preference for grasping

Handedness questionnaires are a common screening tool in psychology and neuroscience, used whenever a participant's performance on a given task may conceivably be affected by their laterality. Two widely-used examples of such questionnaires are the Edinburgh Handedness Inventory and the Waterloo Handedness Questionnaire. Both instruments ask respondents to report their hand preference for performing a variety of common tasks (e.g., throwing a ball, or opening a drawer). Here we combined questions from the two instruments (E-WHQ; 22 questions total) and asked participants to report their preferred hand for each via a five-point scale. The purpose of this study was to determine whether responses on the E-WHQ are accurate, reliable, and/or predictive of hand-preference for a simple grasp-to-construct task. Regarding accuracy, handedness scores were 5% lower when participants used a scrambled response key versus a consistent one. Test-retest reliability of the questionnaire was weak, with any given inventory item eliciting a different response from 34% of respondents upon retesting. Neither was the E-WHQ predictively useful-although both left- and right-handers preferred their dominant hands, E-WHQ score did not correlate with overall percentage of dominant-hand grasps in either group. We conclude that the E-WHQ is unsuited for predicting hand preference for grasping.

Preliminary validation of the Portuguese Edinburgh Handedness Inventory in an adult sample

The Edinburgh Handedness Inventory (EHI) is persistently the most used inventory to evaluate handedness, being neuropsychological investigation and clinical practice. Despite this, there is no information on how this instrument functions in a Portuguese population. The objective of this study was therefore to examine the sociodemographic influences on handedness and establish psychometric properties of the EHI in a Portuguese sample. The sample consisted of 342 adults (157 men and 185 women), assessed with a battery of neuropsychological tests. The mean EHI Laterality Quotient was 63.52 (SD = 38.00). A much high percentage of ambiguous-handedness compared to left-handedness was detected. An inconsistency was found between the preference for formal education activities (writing-drawing-using scissors) and the remaining EHI activities. From sociodemographic variables, only age, area, and regions of residence showed significant influence on EHI scores. The reliability and temporal reliability of EHI were adequate. Confirmatory factor analysis indicated a one-factor model (χ²/df = 2.141; TLI = 0.972; CFI = 0.979; RMSEA = 0.058). The inconsistency between formal education and nonformal activities could be an indicator of social pressure. The present data give support for the notion that handedness measured by EHI is potentially sensitive to sociodemographic and cultural influences.

Evidence for general right-, mixed-, and left-sidedness in self-reported handedness, footedness, eyedness, and earedness, and a primacy of footedness in a large-sample latent variable analysis

Lateral preferences are important for the study of cerebral lateralization and may be indicative of neurobehavioral disorders, neurodevelopmental instability, and deficits in lateralization. Previous studies showed that self-reported preferences are also concordantly interrelated, suggesting a common genetic or biological origin, sidedness. However, with regard to the assessment and classification of lateral preferences, there is a dearth of psychometric studies, but a need for psychometrically validated instruments that can be reliably used in applied research. Based on three independent large samples (total N>15,100), this study investigated the psychometric properties of widely-used lateral preference scales of handedness, footedness, eyedness, and earedness. Preferences were consistently and replicably categorical, consisting of right, mixed, and left preferences each, underlining that primarily qualitative, rather than quantitative, differences differentiate lateral preferences. Right-, mixed-, and left-sidedness underlay the individual preferences, but sidedness alone could not fully explain the observed inter-relations. Footedness was the single most important indicator of sidedness. Our data were further consistent with predictions of right shift theory and corroborated a 'pull-to-concordance' in hand-foot preferences. We recommend the use of psychometrically validated scales and of a trichotomous classification of lateral preferences in future research, but conclude that handedness may be a biased indicator of underlying sidedness. Footedness needs to be examined more closely with regard to cerebral lateralization, neurodevelopmental disorders, and neurodevelopmental instability.

Differences between left- and right-handers in approach/avoidance motivation: influence of consistency of handedness measures

Hand preference is often viewed as a troublesome variable in psychological research, with left-handers routinely excluded from studies. Contrary to this, a body of evidence has shown hand preference to be a useful variable when examining human behavior. A recent review argues that the most effective way of using handedness as a variable, is a comparison between individuals who use their dominant hand for virtually all manual activities (consistent handers) versus those who use their other hand for at least one activity (inconsistent handers). The authors contend that researchers should only focus on degree of handedness rather than direction of preference (left versus right). However, we argue that the field suffers from a number of methodological and empirical issues. These include a lack of consensus in choice of cut-off point to divide consistent and inconsistent categories and importantly a paucity of data from left-handers. Consequentially, researchers predominantly compare inconsistent versus consistent right-handers, largely linked to memory, cognition and language. Other research on response style and personality measures shows robust direction of handedness effects. The present study examines both strength and direction of handedness on self-reported behavioral inhibition system (BIS) and behavioral activation system (BAS) scores, using evidence from a large (N = 689) dataset including more than 200 left-handers. There were degree of handedness effects on BIS and BAS-Fun Seeking, but effects are largely driven by differences between consistent left-handers and other groups. Choice of cut-off point substantively influenced results, and suggests that unless a suitable sample of left-handers is included, researchers clarify that their degree of handedness effects are applicable only to right-handers. We concur that strength of hand preference is an important variable but caution that differences related to consistency may not be identical in right and left-handers.

Categories versus dimensions in personality and psychopathology: a quantitative review of taxometric research

Taxometric research methods were developed by Paul Meehl and colleagues to distinguish between categorical and dimensional models of latent variables. We have conducted a comprehensive review of published taxometric research that included 177 articles, 311 distinct findings and a combined sample of 533 377 participants. Multilevel logistic regression analyses have examined the methodological and substantive variables associated with taxonic (categorical) findings. Although 38.9% of findings were taxonic, these findings were much less frequent in more recent and methodologically stronger studies, and in those reporting comparative fit indices based on simulated comparison data. When these and other possible confounds were statistically controlled, the true prevalence of taxonic findings was estimated at 14%. The domains of normal personality, mood disorders, anxiety disorders, eating disorders, externalizing disorders, and personality disorders (PDs) other than schizotypal yielded little persuasive evidence of taxa. Promising but still not definitive evidence of psychological taxa was confined to the domains of schizotypy, substance use disorders and autism. This review indicates that most latent variables of interest to psychiatrists and personality and clinical psychologists are dimensional, and that many influential taxonic findings of early taxometric research are likely to be spurious.

[Left-handedness and health]

Hand dominance is defined as a proneness to use one hand rather than another in performing the majority of activities and this is the most obvious example of cerebral lateralization and an exclusive human characteristic. Left-handed people comprise 6-14% of the total population, while in Serbia, this percentage is 5-10%, moving from undeveloped to developed environments, where a socio-cultural pressure is less present. There is no agreement between investigators who in fact may be considered a left-handed person, about the percentage of left-handers in the population and about the etiology of left-handedness. In the scientific literature left-handedness has been related to health disorders (spine deformities, immunological disorders, migraine, neurosis, depressive psychosis, schizophrenia, insomnia, homosexuality, diabetes mellitus, arterial hypertension, sleep apnea, enuresis nocturna and Down Syndrome), developmental disorders (autism, dislexia and sttutering) and traumatism. The most reliable scientific evidences have been published about the relationship between left-handedness and spinal deformities in school children in puberty and with traumatism in general population. The controversy of other results in up-to-now investigations of health aspects of left-handedness may partly be explained by a scientific disagreement whether writing with the left hand is a sufficient criterium for left-handedness, or is it necessary to investigate other parameters for laterality assessment. Explanation of health aspects of left-handedness is dominantly based on Geschwind-Galaburda model about "anomalous" cerebral domination, as a consequence of hormonal disbalance.