| 1. |
- Arnett, Anne, et al.
(author)
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A cross-lagged model of the development of ADHD inattention symptoms and rapid naming speed
- 2012
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In: Journal of Abnormal Child Psychology. - : Springer. - 0091-0627 .- 1573-2835. ; 40:8, s. 1313-1326
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Journal article (peer-reviewed)abstract
- Although previous research has identified contemporaneous associations between cognitive deficits and symptom phenotypes in Attention Deficit/Hyperactivity Disorder, no studies have as yet attempted to identify direction of effect. The present study used cross-lagged path modeling to examine competing hypotheses about longitudinal associations between rapid naming speed and symptoms of inattention in children. 1,506 school-age twins from Australia and the U.S. were tested for inattention, hyperactivity/impulsivity, and rapid naming speed at three and four time points, respectively. Symptom severity of inattention from Kindergarten to fourth grade is consistently predicted by previous rapid naming, over and above auto-regressive and correlational associations in the model. Likewise, inattention symptoms have a small but significant predictive effect on subsequent rapid naming. The findings support a reciprocal relationship between naming speed and ADHD inattentive symptoms.
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| 2. |
- Arnett, Anett, et al.
(author)
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The SWAN captures variance at the negative and positive ends of the ADHD Symptom dimension
- 2013
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In: Journal of Attention Disorders. - : Sage Publications. - 1087-0547 .- 1557-1246. ; 17:2, s. 152-162
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Journal article (peer-reviewed)abstract
- Objective: The Strengths and Weaknesses of ADHD Symptoms and Normal Behavior (SWAN) Rating Scale differs from previous parent reports of ADHD in that it was designed to also measure variability at the positive end of the symptom spectrum. Method: The psychometric properties of the SWAN were tested and compared with an established measure of ADHD, the Disruptive Behavior Rating Scale (DBRS). Results: The SWAN demonstrates comparable validity, reliability, and heritability to the DBRS. Furthermore, plots of the SWAN and DBRS reveal heteroscedasticity, which supports the SWAN as a preferred measure of positive attention and impulse regulation behaviors. Conclusion: The ability of the SWAN to measure additional variance at the adaptive end of the ADHD symptom dimensions makes it a promising tool for behavioral genetic studies of ADHD.
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| 3. |
- Christopher, Micaela E., et al.
(author)
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Predicting Word Reading and Comprehension With Executive Function and Speed Measures Across Development: A Latent Variable Analysis
- 2012
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In: Journal of experimental psychology. General. - : American Psychological Association. - 0096-3445 .- 1939-2222. ; 141:3, s. 470-488
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Journal article (peer-reviewed)abstract
- The present study explored whether different executive control and speed measures (working memory, inhibition, processing speed, and naming speed) independently predict individual differences in word reading and reading comprehension. Although previous studies suggest these cognitive constructs are important for reading, the authors analyze the constructs simultaneously to test whether each is a unique predictor. Latent variables from 483 participants (ages 8-16 years) were used to portion each cognitive and reading construct into its unique and shared variance. In these models 2 specific issues are addressed: (a) Given that the wide age range may span the theoretical transition from "learning to read" to "reading to learn," the authors first test whether the relation between word reading and reading comprehension is stable across 2 age groups (ages 8-10 and 11-16); and (b) the main theoretical question of interest: whether what is shared and what is separable for word reading and reading comprehension are associated with individual differences in working memory, inhibition, and measures of processing and naming speed. The results indicated that (a) the relation between word reading and reading comprehension is largely invariant across the age groups, and (b) working memory and general processing speed, but not inhibition or the speeded naming of nonalphanumeric stimuli, are unique predictors of both word reading and comprehension, with working memory equally important for both reading abilities and processing speed more important for word reading. These results have implications for understanding why reading comprehension and word reading are highly correlated yet separable.
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| 4. |
- Christopher, Micaela, et al.
(author)
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Genetic and environmental etiologies of the longitudinal relations between prereading skills and reading
- 2015
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In: Child Development. - : Wiley. - 0009-3920 .- 1467-8624. ; 86:2, s. 342-361
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Journal article (peer-reviewed)abstract
- The present study explored the environmental and genetic etiologies of the longitudinal relations between prereading skills and reading and spelling. Twin pairs (n = 489) were assessed before kindergarten (M = 4.9 years), post-first grade (M = 7.4 years), and post-fourth grade (M = 10.4 years). Genetic influences on five prereading skills (print knowledge, rapid naming, phonological awareness, vocabulary, and verbal memory) were primarily responsible for relations with word reading and spelling. However, relations with post-fourth-grade reading comprehension were due to both genetic and shared environmental influences. Genetic and shared environmental influences that were common among the prereading variables covaried with reading and spelling, as did genetic influences unique to verbal memory (only post-fourth-grade comprehension), print knowledge, and rapid naming.
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| 5. |
- Christopher, Micaela, et al.
(author)
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Modeling the etiology of individual differences in early reading development : Evidence for strong genetic influences
- 2013
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In: Scientific Studies of Reading. - : Routledge. - 1088-8438 .- 1532-799X. ; 17:5, s. 350-368
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Journal article (peer-reviewed)abstract
- We explored the etiology of individual differences in reading development from post-kindergarten to post–4th grade by analyzing data from 487 twin pairs tested in Colorado. Data from three reading measures and one spelling measure were fit to biometric latent growth curve models, allowing us to extend previous behavioral genetic studies of the etiology of early reading development at specific time points. We found primarily genetic influences on individual differences at post–1st grade for all measures. Genetic influences on variance in growth rates were also found, with evidence of small, nonsignificant, shared environmental influences for two measures. We discuss our results, including their implications for educational policy.
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| 6. |
- Christopher, Micaela, et al.
(author)
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The genetic and environmental etiologies of individual differences in early reading growth in Australia, the United States and Scandinavia
- 2013
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In: Journal of experimental child psychology (Print). - : Elsevier. - 0022-0965 .- 1096-0457. ; 115:3, s. 453-467
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Journal article (peer-reviewed)abstract
- This first cross-country twin study of individual differences in reading growth from post-kindergarten to post-second grade analyzed data from 487 twin pairs from the United States, 267 twin pairs from Australia, and 280 twin pairs from Scandinavia. Data from two reading measures were fit to biometric latent growth models. Individual differences for the reading measures at post-kindergarten in the United States and Australia were due primarily to genetic influences and to both genetic and shared environmental influences in Scandinavia. In contrast, individual differences in growth generally had large genetic influences in all countries. These results suggest that genetic influences are largely responsible for individual differences in early reading development. In addition, the timing of the start of formal literacy instruction may affect the etiology of individual differences in early reading development but have only limited influence on the etiology of individual differences in growth.
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| 7. |
- Householder, John Ethan, et al.
(author)
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One sixth of Amazonian tree diversity is dependent on river floodplains
- 2024
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In: NATURE ECOLOGY & EVOLUTION. - 2397-334X. ; 8, s. 901-911
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Journal article (peer-reviewed)abstract
- Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.
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| 8. |
- Luize, Bruno Garcia, et al.
(author)
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Geography and ecology shape the phylogenetic composition of Amazonian tree communities
- 2024
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In: JOURNAL OF BIOGEOGRAPHY. - 0305-0270 .- 1365-2699. ; 51:7, s. 1163-1184
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Journal article (peer-reviewed)abstract
- Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and v & aacute;rzea forest types, the phylogenetic composition varies by geographic region, but the igap & oacute; and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R-2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R-2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.
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| 9. |
- MacDonald, Beatriz, et al.
(author)
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Cross-Country Differences in Parental Reporting of Symptoms of ADHD
- 2019
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In: Journal of Cross-Cultural Psychology. - : Sage Publications. - 0022-0221 .- 1552-5422. ; 50:6, s. 806-824
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Journal article (peer-reviewed)abstract
- Previous studies within the United States suggest there are cultural and contextual influences on how attention-deficit/hyperactivity disorder (ADHD) symptoms are perceived. If such influences operate within a single country, they are likely to also occur between countries. In the current study, we tested whether country differences in mean ADHD scores also reflect cultural and contextual differences, as opposed to actual etiological differences. The sample for the present study included 974 participants from four countries tested at two time points, the end of preschool and the end of second grade. Consistent with previous research, we found lower mean ADHD scores in Norway and Sweden in comparison with Australia and the United States, and we tested four explanations for these country differences: (a) genuine etiological differences, (b) slower introduction to formal academic skills in Norway and Sweden than in the United States and Australia that indicated a context difference, (c) underreporting tendency in Norway and Sweden, or (d) overreporting tendency in the United States and Australia. Either under- or overreporting would be examples of cultural differences in the perception of ADHD symptoms. Of these explanations, results of ADHD measurement equivalence tests across countries rejected the first three explanations and supported the fourth explanation: an overreporting tendency in the United States and Australia. These findings indicate that parental reporting of ADHD symptoms is more accurate in Norway and Sweden than in Australia and the United States, and, thus, have important clinical and educational implications for how parental reporting informs an ADHD diagnosis in these countries.
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| 10. |
- Miller, Amanda C, et al.
(author)
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Reading Comprehension in Children with ADHD: Cognitive Underpinnings of the Centrality Deficit
- 2013
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In: Journal of Abnormal Child Psychology. - : Springer Verlag (Germany). - 0091-0627 .- 1573-2835. ; 41:3, s. 473-483
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Journal article (peer-reviewed)abstract
- We examined reading comprehension in children with ADHD by assessing their ability to build a coherent mental representation that allows them to recall central and peripheral information. We compared children with ADHD (mean age 9.78) to word reading-matched controls (mean age 9.89) on their ability to retell a passage. We found that even though children with ADHD recalled more central than peripheral information, they showed their greatest deficit, relative to controls, on central information-a centrality deficit (Miller and Keenan, Annals of Dyslexia 59:99-113, 2009). We explored the cognitive underpinnings of this deficit using regressions to compare how well cognitive factors (working memory, inhibition, processing speed, and IQ) predicted the ability to recall central information, after controlling for word reading ability, and whether these cognitive factors interacted with ADHD symptoms. Working memory accounted for the most unique variance. Although previous evidence for reading comprehension difficulties in children with ADHD have been mixed, this study suggests that even when word reading ability is controlled, children with ADHD have difficulty building a coherent mental representation, and this difficulty is likely related to deficits in working memory.
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| 11. |
- Olson, Richard, et al.
(author)
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Genetic and Environmental Influences on Vocabulary and Reading Development
- 2011
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In: SCIENTIFIC STUDIES OF READING. - : Taylor and Francis. - 1088-8438 .- 1532-799X. ; 15:1, s. 26-46
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Journal article (peer-reviewed)abstract
- Genetic and environmental relations between vocabulary and reading skills were explored longitudinally from preschool through Grades 2 and 4. At preschool there were strong shared-environment and weak genetic influences on both vocabulary and print knowledge but substantial differences in their source. Separation of etiology for vocabulary and reading continued for word recognition and decoding through Grade 4, but genetic and environmental correlations between vocabulary and reading comprehension approached unity by Grade 4, when vocabulary and word recognition accounted for all of the genetic and shared environment influences on reading comprehension.
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| 12. |
- Pennington, Bruce, et al.
(author)
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Individual prediction of dyslexia by single vs. multiple deficit models.
- 2012
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In: Journal of Abnormal Psychology. - : American Psychological Association. - 0021-843X .- 1939-1846. ; 121:1, s. 212-224
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Journal article (peer-reviewed)abstract
- The overall goals of this study were to test single versus multiple cognitive deficit models of dyslexia (reading disability) at the level of individual cases and to determine the clinical utility of these models for prediction and diagnosis of dyslexia. To accomplish these goals, we tested five cognitive models of dyslexia-two single-deficit models, two multiple-deficit models, and one hybrid model-in two large population-based samples, one cross-sectional (Colorado Learning Disability Research Center) and one longitudinal (International longitudinal Twin Study). The cognitive deficits included in these cognitive models were in phonological awareness, language skill, and processing speed and/or naming speed. To determine whether an individual case fit one of these models, we used two methods: 1) the presence or absence of the predicted cognitive deficits, and 2) whether the individuals level of reading skill best fit the regression equation with the relevant cognitive predictors (i.e., whether their reading skill was proportional to those cognitive predictors.) We found that roughly equal proportions of cases met both tests of model fit for the multiple deficit models (30-36%) and single deficit models (24-28%); hence, the hybrid model provided the best overall fit to the data. The remaining roughly 40% of cases in each sample lacked the deficit or deficits that corresponded with their best-fitting regression model. We discuss the clinical implications of these results for both diagnosis of school-age children and preschool prediction of children at risk for dyslexia.
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| 13. |
- Peterson, Robin L, et al.
(author)
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Literacy acquisition influences children's rapid automatized naming
- 2018
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In: Developmental Science. - : Wiley-Blackwell Publishing Inc.. - 1363-755X .- 1467-7687. ; 21:3
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Journal article (peer-reviewed)abstract
- Previous research has established that learning to read improves children's performance on reading‐related phonological tasks, including phoneme awareness (PA) and nonword repetition. Few studies have investigated whether literacy acquisition also promotes children's rapid automatized naming (RAN). We tested the hypothesis that literacy acquisition should influence RAN in an international, longitudinal population sample of twins. Cross‐lagged path models evaluated the relationships among literacy, PA, and RAN across four time points from pre‐kindergarten through grade 4. Consistent with previous research, literacy showed bidirectional relationships with reading‐related oral language skills. We found novel evidence for an effect of earlier literacy on later RAN, which was most evident in children at early phases of literacy development. In contrast, the influence of earlier RAN on later literacy was predominant among older children. These findings imply that the association between these two related skills is moderated by development. Implications for models of reading development and for dyslexia research are discussed.
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| 14. |
- Peterson, Robin, et al.
(author)
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Shared etiology of phonological memory and vocabulary deficits in school-age children
- 2013
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In: Journal of Speech, Language and Hearing Research. - : American Speech-Language-Hearing Association. - 1092-4388 .- 1558-9102. ; 56:4, s. 1249-1259
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Journal article (peer-reviewed)abstract
- Purpose: The goal of this study was to investigate the etiologic basis for the association between deficits in phonological memory (PM) and vocabulary in school-age children.Method: Children with deficits in PM or vocabulary were identified within the International Longitudinal Twin Study (ILTS; Samuelsson et al., 2005). The ILTS includes 1,045 twin pairs (between the ages of 5 and 8 years) from the United States, Australia, and Scandinavia. The authors applied the DeFries-Fulker ( DeFries & Fulker, 1985, 1988) regression method to determine whether problems in PM and vocabulary tend to co-occur because of overlapping genes, overlapping environmental risk factors, or both.Results: Among children with isolated PM deficits, the authors found significant bivariate heritability of PM and vocabulary weaknesses both within and across time. However, when probands were selected for a vocabulary deficit, there was no evidence for bivariate heritability. In this case, it appears that the PM–vocabulary relationship is caused by common shared environmental experiences.Conclusions: The findings are consistent with previous research on the heritability of specific language impairment and suggest that there are etiologic subgroups of children with low vocabulary for different reasons, 1 being more influenced by genes and another being more influenced by environment.
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| 15. |
- ter Steege, Hans, et al.
(author)
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Mapping density, diversity and species-richness of the Amazon tree flora
- 2023
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In: COMMUNICATIONS BIOLOGY. - 2399-3642. ; 6:1
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Journal article (peer-reviewed)abstract
- Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution. A study mapping the tree species richness in Amazonian forests shows that soil type exerts a strong effect on species richness, probably caused by the areas of these forest types. Cumulative water deficit, tree density and temperature seasonality affect species richness at a regional scale.
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| 16. |
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