Sex differences in early verbal and non‐verbal cognitive development

The present study of over 3000 2‐year‐old twin pairs used a sex‐limitation model to examine genetic and environmental origins of sex differences in verbal and non‐verbal cognitive ability. Girls scored significantly higher on both measures (p<0.0001), although gender only accounted for approximately 3% of the variance in verbal ability and 1% of the variance in non‐verbal cognitive ability. For the verbal measure boys showed greater heritability than girls. Also the twin‐pair correlation is significantly lower for opposite‐sex twins than for non‐identical same‐sex twins. This indicates that individual differences in verbal ability include some sex‐specific factors. Non‐verbal cognitive ability did not differ in aetiology for boys and girls. We conclude that genetic and environmental influences differ for girls and boys for early verbal but not non‐verbal development.     

Genetic and environmental origins of verbal and performance components of cognitive delay in 2-year-olds.

The authors investigated the etiology of several measures of cognitive delay. Verbal (V) and performance (P) abilities were assessed in over 3,000 pairs of 2-year-old twins. Group-differences heritability for general delay (the lowest 5% of the V and P composite) was 35%. However, V and P delays considered independently showed large differences in group heritability (77% for V vs. 40% for P). Specific delays with comorbid cases eliminated showed an even greater difference in group heritability (78% vs. 22%, respectively). The small sample comorbid for both V and P delay also yielded high group heritability for both V (77%) and P (93%) scores. Shared environmental factors also differed in magnitude for V (20%) and P (41%) delays. Because the genetic and environmental origins of V and P delays in infancy differ, they are better considered separately rather than combined into a composite measure of general cognitive delay.     

Repeated interrogations: verbal and non‐verbal cues to deception

The major aim of this study was to investigate to what extent verbal and non‐verbal features of liars' and truth‐tellers' behaviour change during the course of repeated interrogations. After seeing a staged event, 24 suspects (12 liars and 12 truth‐tellers) were interrogated three times over a period of 11 days. In terms of the non‐verbal features, and in line with our prediction, we found that the liars displayed significantly fewer smiles, self‐manipulations, pauses, and less gaze aversion than truth‐tellers. Furthermore, over time the initial differences between liars' and truth‐tellers' non‐verbal behaviour increased for smiles, gaze aversion and pauses. In addition, we found that the cue ‘richness of detail’—the most indicative verbal marker for truth as given in previous research—had no discriminative power at any of the interrogation sessions. Finally, and in contrast to beliefs held by supposed expert lie‐catchers (e.g. judges and police officers), truthful and deceptive statements were found to be equally consistent over time. The psycho‐legal implications of the above findings are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Two‐year‐olds are vigilant of others’ non‐verbal cues to credibility

Data from three experiments provide the first evidence that children, at least as young as age two, are vigilant of others’ non‐verbal cues to credibility, and flexibly use these cues to facilitate learning. Experiment 1 revealed that 2‐ and 3‐year‐olds prefer to learn about objects from someone who appears, through non‐verbal cues, to be confident in performing actions on those objects than from someone who appears uncertain when performing actions on those objects. Experiment 2 revealed that when 2‐year‐olds observe only one model perform a single action, either confidently or unconfidently, they do not use the model’s level of confidence in this single instance to influence their learning. Experiment 3 revealed that 2‐year‐olds will use a single model’s level of confidence to guide their learning if they have observed that the model has a history of being either consistently confident or consistently uncertain. These findings reveal that young children selectively alter their learning based on others’ non‐verbal cues of credibility, and underscore the importance of an early sensitivity to socio‐cognitive cues for human learning and development.     

Masculine girls and feminine boys: genetic and environmental contributions to atypical gender development in early childhood

In this genetic study of atypical gender role development, parents of 5,799 twin pairs, ages 3 and 4, rated their twin children's masculinity and femininity. Boys were selected as gender atypical if they were highly feminine (top 5%, 10%, or 15%) relative to other boys, and girls were selected if they were highly masculine relative to other girls. Gender-atypical boys and girls were each divided into 2 groups: fully gender atypical (e.g., feminine boys also low on masculinity) and partially gender atypical (e.g., feminine boys who are not low on masculinity). DeFries-Fulker (DF; J. C. DeFries & D. W. Fulker, 1985, 1988) extremes analysis yielded moderate group heritability and substantial shared environment effects for atypical gender role behavior. However, for fully gender-atypical girls, group heritability accounted for most of the variance, and shared environment had no effect. The results are discussed in light of past studies and potential implications for atypical gender development.     

Genetic architecture of verbal abilities in children and adolescents

The etiology of individual differences in general verbal ability, verbal learning and letter and category fluency were examined in two independent samples of 9‐ and 18‐year‐old twin pairs and their siblings. In both age groups, we observed strong familial resemblance for general verbal ability and moderate familial resemblance for verbal learning, letter and category fluency. All familial resemblance was explained by genetic factors. There was significant covariance among the tests, which was stronger in magnitude in the adolescent cohort. The covariance was mainly explained by genetic effects shared by subtests, both in middle childhood and in late adolescence. In addition to a shared set of genes that influenced all phenotypes, there were also genetic influences specific to the different verbal phenotypes.     

The semantic‐similarity effect in children: Influence of long‐term knowledge on verbal short‐term memory

The present research was designed to highlight the relation between children's categorical knowledge and their verbal short‐term memory (STM) performance. To do this, we manipulated the categorical organization of the words composing lists to be memorized by 5‐ and 9‐year‐old children. Three types of word list were drawn up: semantically similar context‐dependent (CD) lists, semantically similar context‐independent (CI) lists, and semantically dissimilar lists. In line with the procedure used by Poirier and Saint‐Aubin (1995) , the dissimilar lists were produced using words from the semantically similar lists. Both 5‐ and 9‐year‐old children showed better recall for the semantically similar CD lists than they did for the unrelated lists. In the semantic similar CI condition, semantic similarity enhanced immediate serial recall only at age 9 but contributed to item information memory both at ages 5 and 9. These results, which indicate a semantic influence of long‐term memory (LTM) on serial recall from age 5, are discussed in the light of current models of STM. Moreover, we suggest that differences between results at 5 and 9 years are compatible with pluralist models of development.     

Investigating the unique predictability and boundary conditions of applicant physical attractiveness and non‐verbal behaviours on interviewer evaluations in job interviews

Through the lens of the dramaturgical perspective, the present study investigated (1) the unique predictability of applicant non‐verbal cues (physical attractiveness and non‐verbal behaviours) on interviewer evaluation, and (2) whether situational variables (i.e., customer‐contact requirement and sex‐type consistency) moderate the relationships between applicant non‐verbal cues and interviewer evaluations. Data were collected from 177 interview sessions held in 39 firms in Taiwan. Results showed that applicant physical attractiveness explained unique variance in interviewer evaluations beyond that explained by applicant verbal content. Moreover, the effect of physical attractiveness became weaker when jobs possessed lower customer‐contact requirements, or when the applicant's gender was inconsistent with the interviewer's sex‐type belief relative to the job. No main or moderating effects, however, were found for non‐verbal behaviours on interviewer evaluations.     

Language Reflects “Core” Cognition: A New Theory About the Origin of Cross‐Linguistic Regularities

The underlying structures that are common to the world's languages bear an intriguing connection with early emerging forms of “core knowledge” (Spelke & Kinzler, 2007), which are frequently studied by infant researchers. In particular, grammatical systems often incorporate distinctions (e.g., the mass/count distinction) that reflect those made in core knowledge (e.g., the non‐verbal distinction between an object and a substance). Here, I argue that this connection occurs because non‐verbal core knowledge systematically biases processes of language evolution. This account potentially explains a wide range of cross‐linguistic grammatical phenomena that currently lack an adequate explanation. Second, I suggest that developmental researchers and cognitive scientists interested in (non‐verbal) knowledge representation can exploit this connection to language by using observations about cross‐linguistic grammatical tendencies to inspire hypotheses about core knowledge.     

Effects of classroom bilingualism on task‐shifting,verbal memory,and word learning in children

We examined the effects of classroom bilingual experience in children on an array of cognitive skills. Monolingual English‐speaking children were compared with children who spoke English as the native language and who had been exposed to Spanish in the context of dual‐immersion schooling for an average of 2 years. The groups were compared on a measure of non‐linguistic task‐shifting; measures of verbal short‐term and working memory; and measures of word learning. The two groups of children did not differ on measures of non‐linguistic task‐shifting and verbal short‐term memory. However, the classroom‐exposure bilingual group outperformed the monolingual group on the measure of verbal working memory and a measure of word learning. Together, these findings indicate that while exposure to a second language in a classroom setting may not be sufficient to engender changes in cognitive control, it can facilitate verbal memory and verbal learning.     

Developmental path between language and autistic‐like impairments: a twin study

Autism spectrum disorders (ASDs) are diagnosed when individuals show impairments in three behavioural domains: communication, social interactions, and repetitive, restrictive behaviours and interests (RRBIs). Recent data suggest that these three sets of behaviours are genetically heterogeneous. Early language delay is strongly associated with ASD, but the basis for this association and the relationship with individual sub‐domains of ASD has not been systematically investigated. In the present study, data came from a population‐based twin sample with language development data at 2–4 years, measured by the MacArthur Communicative Development Inventory (MCDI), and data at 8 years using the Childhood Asperger Syndrome Test (CAST). For the total CAST and the three subscales at 8 years, approximately 300 same‐sex twin pairs were selected as showing extreme autistic‐like traits (ALTs), defined here as pairs in which at least one member of the twin pair scored in the highest 5% of the distribution. Phenotypic analyses indicated that children showing extreme social and communication ALTs (but not the RRBI subscale) at 8 years were below average in language development at 2–4 years. A regression model for selected twin data suggested that genetic influences account for this overlap, but that these effects are only in part mediated by genes that are shared between language and extreme autistic traits. Copyright © 2008 John Wiley & Sons, Ltd.     

Long‐term memory effects on verbal short‐term memory: A replication study

The influence of lexico‐semantic language representations stored in long‐term memory (LTM) on short‐term memory (STM) performance has been studied extensively in adults. However, there are relatively few data on lexico‐semantic LTM effects on STM in children. On the other hand, the influence of phonological LTM effects on STM has been studied more extensively in children than in adults. In this study, we explored whether these different LTM effects on verbal STM could be replicated in both adults and children by administering immediate serial recall tasks (ISR) for high‐ and lowfrequency words, for high‐ and low‐imageability words, for words and non‐words, and for high and low phonotactic frequency non‐words to 6‐, 8‐, and 10‐year‐old children, to adolescents and to adults. Significant word frequency, lexicality and phonotactic frequency effects were observed in all age groups, as well as a word imageability effect which was, however, weaker than the other three effects. Our data suggest that LTM effects on STM are equivalent in both children and adults.     

Executive functioning deficits in relation to symptoms of ADHD and/or ODD in preschool children

The present study investigated the relation between executive functioning and symptoms of Attention‐Deficit/Hyperactivity Disorder (ADHD) and Oppositional Defiant Disorder (ODD) in children aged 4–6. A population‐based sample (n=201) was used and laboratory measures of inhibition, working memory and verbal fluency and teacher ratings of disruptive behaviour problems were collected. Both group differences and linear relations were studied and comorbidity was controlled for dimensionally. In both categorical and dimensional analyses, executive functioning was associated with symptoms of ADHD, but not with symptoms of ODD when controlling for comorbidity, and no significant interactive effects of ADHD and ODD symptoms were found. Effect sizes for significant effects were generally in the medium range. Regarding sex differences, the control for comorbid ODD symptoms appeared to affect the relation between ADHD symptoms and executive functioning somewhat more for girls compared with boys. In conclusion, poor executive functioning in preschool appears to be primarily related to symptoms of ADHD, whereas the relation to symptoms of ODD can be attributed to the large overlap between these two disruptive disorders. Copyright © 2006 John Wiley & Sons, Ltd.     

Talking about proportion: Fraction labels impact numerical interference in non‐symbolic proportional reasoning

Across two experiments, we investigated how verbal labels impact the way young children attend to proportional information, well before the introduction of formal fraction education. Five‐ to seven‐year‐old children were introduced to equivalent non‐symbolic proportions labeled in one of three ways: (a) a single, categorical label for multiple fractions (both 3/4 and 6/8 referred to as “blick”), (b) labels that focused on the numerator [e.g., 3/4 labeled as “three blicks” (Experiment 1) or “three‐fourths” (Experiment 2)], or (c) labels that had a complete part‐whole structure (“three‐out‐of‐four”). Children then completed measures of non‐symbolic proportional reasoning that pitted whole‐number information against proportional information for novel proportions. Across both experiments, children who heard the categorical labels were more likely to match non‐symbolic displays based on proportion than children in any of the other conditions, who demonstrated higher levels of numerical interference. These findings suggest that fraction labels have the potential to shape children's attention to proportional information even in the context of non‐symbolic part‐whole displays and for children who are not familiar with formal fraction symbols. We discuss these findings in terms of children's developing understanding of proportional reasoning and its implications for fraction education.     

Children extend both words and non‐verbal actions to novel exemplars

Markson and Bloom (1997) found that some learning processes involved in children's acquisition of a new word are also involved in their acquisition of a new fact. They argued that these findings provided evidence against a domain‐specific system for word learning. However, Waxman and Booth (2000) found that whereas children quite readily extend newly learned words to novel exemplars within a category, they do not do this with newly learned facts. They therefore argued that because children did not extend some facts in a principled way, word learning and fact learning may result from different domain‐specific processes. In the current study, we argue that facts are a poor comparison in this argument since facts vary in whether they are tied to particular individuals. A more appropriate comparison is a conventional non‐verbal action on an object –‘what we do with things like this’– since they are routinely generalized categorically to new objects. Our study shows that 2¹/₂‐year‐old children extend novel non‐verbal actions to new objects in the same way that they extend novel words to new objects. The findings provide support for the view that word learning represents a unique configuration of more general learning processes.     

Genetic and environmental influences on pre‐schizophrenic personality: MAXCOV‐HITMAX and LISREL analyses

Postulating that the predisposition to illness in Claridge's disease model of schizophrenia can be equated with the personality dimensions S or Insensitivity, (low) E or Extraversion, and N or Neuroticism, as measured by Van Kampen's 3DPT, and assuming that the mode of transmission of schizophrenia is basically polygenic, the genetic and environmental etiology of S, E, and N was assessed in a sample of 52 MZ and 76 DZ twin pairs and their parents by means of LISREL. Besides, in a sample of 2118 subjects MAXCOV–HITMAX analyses were conducted for these factors as well as for the personality dimension G or Orderliness, but now assessed by the 4DPT, in order to find out whether a discrete or quasi‐discrete variable might also underlie these dimensions, giving support to the possibility of dominance or epistasis. The results obtained in these investigations favoured a model for all three dimensions, allowing for both additive and non‐additive genetic effects in combination with non‐shared environmental influences. It was not possible to choose between a model involving dominance and a model involving epistatic genetic effects. With the use of scores corrected for sex and age, which were converted to normal scores, the proportion of variance explained by additive genetic factors was 20% for S, 40–41% for E, and 26–29% for N. Dominance or multiple‐gene epistasis accounted for 37–38% (S), 19–20% (E), and 30–31% (N), and unshared environmental influences for 42–43% (S), 41% (E), and 42–43% (N) respectively. Copyright © 1999 John Wiley & Sons, Ltd.     

Suicide Ideations,Suicide Attempts,and Completed Suicide in Persons with Pathological Gambling and Their First‐Degree Relatives

We examined the relationship between suicidal ideations and attempts in 95 probands with pathological gambling (PG), 91 controls, and 1075 first‐degree relatives. The results were analyzed using logistic regression with generalized estimating equations. Thirty‐four PG probands (35.8%) and 4 controls (4.4%) had attempted suicide (OR = 12.12, p < .001); in 13 probands, the attempt occurred before PG onset. Lifetime suicidal ideations occurred in 60 PG probands (63.2%) and 12 controls (13.2%) (OR = 11.29, p < .001). Suicidality in PG probands is a marker of PG severity and is associated with greater psychiatric comorbidity. Offspring of PG probands had significantly higher rates of suicide attempts than control offspring.     

Non‐ignorable missingness item response theory models for choice effects in examinee‐selected items

Examinee‐selected item (ESI) design, in which examinees are required to respond to a fixed number of items in a given set, always yields incomplete data (i.e., when only the selected items are answered, data are missing for the others) that are likely non‐ignorable in likelihood inference. Standard item response theory (IRT) models become infeasible when ESI data are missing not at random (MNAR). To solve this problem, the authors propose a two‐dimensional IRT model that posits one unidimensional IRT model for observed data and another for nominal selection patterns. The two latent variables are assumed to follow a bivariate normal distribution. In this study, the mirt freeware package was adopted to estimate parameters. The authors conduct an experiment to demonstrate that ESI data are often non‐ignorable and to determine how to apply the new model to the data collected. Two follow‐up simulation studies are conducted to assess the parameter recovery of the new model and the consequences for parameter estimation of ignoring MNAR data. The results of the two simulation studies indicate good parameter recovery of the new model and poor parameter recovery when non‐ignorable missing data were mistakenly treated as ignorable.