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Genetic Correlation
In multivariate quantitative genetics, a genetic correlation (denoted r_g or r_a) is the proportion of variance that two traits share due to genetic causes, the correlation between the genetic influences on a trait and the genetic influences on a different trait Plomin et al., p. 123 estimating the degree of pleiotropy or causal overlap. A genetic correlation of 0 implies that the genetic effects on one trait are independent of the other, while a correlation of 1 implies that all of the genetic influences on the two traits are identical. The bivariate genetic correlation can be generalized to inferring genetic latent variable factors across > 2 traits using factor analysis. Genetic correlation models were introduced into behavioral genetics in the 1970s–1980s. Genetic correlations have applications in validation of genome-wide association study (GWAS) results, breeding, prediction of traits, and discovering the etiology of traits & diseases. They can be estimated using indiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heritability
Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of ''variation'' in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is ''not'' explained by the environment or random chance?" Other causes of measured variation in a trait are characterized as environmental factors, including observational error. In human studies of heritability these are often apportioned into factors from "shared environment" and "non-shared environment" based on whether they tend to result in persons brought up in the same household being more or less similar to persons who were not. Heritability is estimated by comparing individual phenotypic variation among related individuals in a population, by examining the association between indiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantitative Genetics
Quantitative genetics deals with phenotypes that vary continuously (such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical). Both branches use the frequencies of different alleles of a gene in breeding populations (gamodemes), and combine them with concepts from simple Mendelian inheritance to analyze inheritance patterns across generations and descendant lines. While population genetics can focus on particular genes and their subsequent metabolic products, quantitative genetics focuses more on the outward phenotypes, and makes only summaries of the underlying genetics. Due to the continuous distribution of phenotypic values, quantitative genetics must employ many other statistical methods (such as the ''effect size'', the ''mean'' and the ''variance'') to link phenotypes (attributes) to genotypes. Some phenotypes may be analyzed either as discrete categories or as continuous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linkage Disequilibrium
In population genetics, linkage disequilibrium (LD) is the non-random association of alleles at different loci in a given population. Loci are said to be in linkage disequilibrium when the frequency of association of their different alleles is higher or lower than what would be expected if the loci were independent and associated randomly. Linkage disequilibrium is influenced by many factors, including selection, the rate of genetic recombination, mutation rate, genetic drift, the system of mating, population structure, and genetic linkage. As a result, the pattern of linkage disequilibrium in a genome is a powerful signal of the population genetic processes that are structuring it. In spite of its name, linkage disequilibrium may exist between alleles at different loci without any genetic linkage between them and independently of whether or not allele frequencies are in equilibrium (not changing with time). Furthermore, linkage disequilibrium is sometimes referred to as gam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Long-term Memory
Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to short-term and working memory, which persist for only about 18 to 30 seconds. Long-term memory is commonly labelled as explicit memory ( declarative), as well as episodic memory, semantic memory, autobiographical memory, and implicit memory ( procedural memory). Dual-store memory model According to Miller, whose paper in 1956 popularized the theory of the "magic number seven", short-term memory is limited to a certain number of chunks of information, while long-term memory has a limitless store. Atkinson–Shiffrin memory model According to the dual store memory model proposed by Richard C. Atkinson and Richard Shiffrin in 1968, memories can reside in the short-term "buffer" for a limited time while they are simultaneously strengthening their associations in long-term memory. When items are first presented, they ente ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Time
Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; sometimes referred to as "response time") is measured by the elapsed time between stimulus onset and an individual's response on elementary cognitive tasks (ETCs), which are relatively simple perceptual-motor tasks typically administered in a laboratory setting. Mental chronometry is one of the core methodological paradigms of human experimental, cognitive, and differential psychology, but is also commonly analyzed in psychophysiology, cognitive neuroscience, and behavioral neuroscience to help elucidate the biological mechanisms underlying perception, attention, and decision-making in humans and other species. Mental chronometry uses measurements of elapsed time between sensory stimulus onsets and subsequent behavioral responses to study the time course of information processing in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spatial Memory
In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Spatial memory is necessary for orientation in space. Spatial memory can also be divided into egocentric and allocentric spatial memory. A person's spatial memory is required to navigate around a familiar city. A rat's spatial memory is needed to learn the location of food at the end of a maze. In both humans and animals, spatial memories are summarized as a cognitive map. Spatial memory has representations within working, short-term memory and long-term memory. Research indicates that there are specific areas of the brain associated with spatial memory. Many methods are used for measuring spatial memory in children, adults, and animals. Short-term spatial memory Short-term memory (STM) can be described as a system allowing one to tempor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Verbal Memory
Verbal memory is a term used in cognitive psychology which refers to memory of words and other abstractions involving language. Verbal encoding Verbal encoding refers to the interpretation of verbal stimuli. Verbal encoding appears to be strongly left- lateralized in the medial temporal lobe of the human brain; however, its functional neuroanatomy can vary between individuals. Verbal recall Verbal recall refers to the recollection of verbal information. Although left-lateralization is typically associated with language, studies suggest that symmetrical bi-lateralization of language in the brain is advantageous to verbal recall.Catani*,†,‡,§, Marco; Allin†, Matthew P.G.; Husain¶, Masud; Pugliese*, Lucas; Mesulam‖, Marsel M.; Murray†, Robin M.; Jones**, Derek K"Symmetries in Human Brain Language Pathways Correlate with Verbal Recall ''Proceedings of the National Academy of Sciences of the United States of America''. See also *Semantic memory *Declarative memory *Sensory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Generalist Genes Hypothesis
The Generalist Genes Hypothesis of learning abilities and disabilities was originally coined in an article by Plomin & Kovas (2005). The Generalist Genes Hypothesis suggests that most genes associated with common learning disabilities Learning disability, learning disorder, or learning difficulty (British English) is a condition in the brain that causes difficulties comprehending or processing information and can be caused by several different factors. Given the "difficult ... and abilities are generalist in three ways. *Firstly, the same genes that influence common learning abilities (e.g., high reading aptitude) are also responsible for common learning disabilities (e.g., reading disability): they are strongly genetically correlated. *Secondly, many of the genes associated with one aspect of a learning disability (e.g., vocabulary problems) also influence other aspects of this learning disability (e.g., grammar problems). *Thirdly, genes that influence one learning disabil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reading Disability
A reading disability is a condition in which a person displays difficulty reading. Examples of reading disabilities include: developmental dyslexia, alexia (acquired dyslexia), and hyperlexia (word-reading ability well above normal for age and IQ). Definition The National Institute of Neurological Disorders and Stroke defines reading disability or dyslexia as follows: "Dyslexia is a brain-based type of learning disability that specifically impairs a person's ability to read. These individuals typically read at levels significantly lower than expected despite having normal intelligence. Although the disorder varies from person to person, common characteristics among people with dyslexia are difficulty with spelling, phonological processing (the manipulation of sounds), and rapid visual-verbal responding. In adults, dyslexia usually occurs after a brain injury or in the context of dementia. It can also be inherited in some families, and recent studies have identified a number of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Architecture
Genetic architecture is the underlying genetic basis of a phenotypic trait and its variational properties. Phenotypic variation for quantitative traits is, at the most basic level, the result of the segregation of alleles at quantitative trait loci (QTL). Environmental factors and other external influences can also play a role in phenotypic variation. Genetic architecture is a broad term that can be described for any given individual based on information regarding gene and allele number, the distribution of allelic and mutational effects, and patterns of pleiotropy, dominance, and epistasis. There are several different experimental views of genetic architecture. Some researchers recognize that the interplay of various genetic mechanisms is incredibly complex, but believe that these mechanisms can be averaged and treated, more or less, like statistical noise. Other researchers claim that each and every gene interaction is significant and that it is necessary to measure and model ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Information Bias (epidemiology)
In epidemiology, information bias refers to bias arising from measurement error. Information bias is also referred to as observational bias and misclassification. ''A Dictionary of Epidemiology'', sponsored by the International Epidemiological Association, defines this as the following: "1. A flaw in measuring exposure, covariate, or outcome variables that results in different quality (accuracy) of information between comparison groups. The occurrence of information biases may not be independent of the occurrence of selection biases. 2. Bias in an estimate arising from measurement errors." Misclassification Misclassification thus refers to measurement error. There are two types of misclassification in epidemiological research: non-differential misclassification and differential misclassification. Nondifferential misclassification Nondifferential misclassification is when all classes, groups, or categories of a variable (whether exposure, outcome, or covariate) have the sam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkson's Paradox
Berkson's paradox, also known as Berkson's bias, collider bias, or Berkson's fallacy, is a result in conditional probability and statistics which is often found to be counterintuitive, and hence a veridical paradox. It is a complicating factor arising in statistical tests of proportions. Specifically, it arises when there is an ascertainment bias inherent in a study design. The effect is related to the explaining away phenomenon in Bayesian networks, and conditioning on a collider in graphical models. It is often described in the fields of medical statistics or biostatistics, as in the original description of the problem by Joseph Berkson. Examples Overview The most common example of Berkson's paradox is a false observation of a ''negative'' correlation between two desirable traits, i.e., that members of a population which have some desirable trait tend to lack a second. Berkson's paradox occurs when this observation appears true when in reality the two properties are unrelate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
