An intelligence quotient (IQ) is a total score derived from a set of standardised tests or subtests designed to assess human intelligence. The abbreviation "IQ" was coined by the psychologist William Stern for the German term Intelligenzquotient, his term for a scoring method for intelligence tests at University of Breslau he advocated in a 1912 book.
Discussions of race and intelligence – specifically regarding claims of differences in intelligence along racial lines – have appeared in both popular science and academic research since the modern concept of race was first introduced. With the inception of IQ testing in the early 20th century, differences in average test performance between racial groups have been observed, though these differences have fluctuated and in many cases steadily decreased over time. Complicating the issue, modern science has concluded that race is a socially constructed phenomenon rather than a biological reality, and there exist various conflicting definitions of intelligence. In particular, the validity of IQ testing as a metric for human intelligence is disputed. Today, the scientific consensus is that genetics does not explain differences in IQ test performance between groups, and that observed differences are environmental in origin.
Human intelligence is the intellectual capability of humans, which is marked by complex cognitive feats and high levels of motivation and self-awareness. Using their intelligence, humans are able to learn, form concepts, understand, and apply logic and reason. Human intelligence is also thought to encompass their capacities to recognize patterns, plan, innovate, solve problems, make decisions, retain information, and use language to communicate.
The g factor is a construct developed in psychometric investigations of cognitive abilities and human intelligence. It is a variable that summarizes positive correlations among different cognitive tasks, reflecting the fact that an individual's performance on one type of cognitive task tends to be comparable to that person's performance on other kinds of cognitive tasks. The g factor typically accounts for 40 to 50 percent of the between-individual performance differences on a given cognitive test, and composite scores based on many tests are frequently regarded as estimates of individuals' standing on the g factor. The terms IQ, general intelligence, general cognitive ability, general mental ability, and simply intelligence are often used interchangeably to refer to this common core shared by cognitive tests. However, the g factor itself is a mathematical construct indicating the level of observed correlation between cognitive tasks. The measured value of this construct depends on the cognitive tasks that are used, and little is known about the underlying causes of the observed correlations.
Neuroscience and intelligence refers to the various neurological factors that are partly responsible for the variation of intelligence within species or between different species. A large amount of research in this area has been focused on the neural basis of human intelligence. Historic approaches to studying the neuroscience of intelligence consisted of correlating external head parameters, for example head circumference, to intelligence. Post-mortem measures of brain weight and brain volume have also been used. More recent methodologies focus on examining correlates of intelligence within the living brain using techniques such as magnetic resonance imaging (MRI), functional MRI (fMRI), electroencephalography (EEG), positron emission tomography and other non-invasive measures of brain structure and activity.
Christopher Richard Brand was a British psychological and psychometric researcher who gained media attention for his controversial statements on race and intelligence and paedophilia.
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 is measured by the elapsed time between stimulus onset and an individual's response on elementary cognitive tasks (ECTs), 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.
Lawrence J. Whalley was a British psychiatrist who was the Crombie Ross Professor of Mental Health in the University of Aberdeen, from 1992 to 2008. He was later a professor emeritus there, and from 2010 to 2020, a part-time professor of research at the University of the Highlands and Islands.
Environment and intelligence research investigates the impact of environment on intelligence. This is one of the most important factors in understanding human group differences in IQ test scores and other measures of cognitive ability. It is estimated that genes contribute about 20–40% of the variance in intelligence in childhood and about 80% in adulthood. Thus the environment and its interaction with genes account for a high proportion of the variation in intelligence seen in groups of young children, and for a small proportion of the variation observed in groups of mature adults. Historically, there has been great interest in the field of intelligence research to determine environmental influences on the development of cognitive functioning, in particular, fluid intelligence, as defined by its stabilization at 16 years of age. Despite the fact that intelligence stabilizes in early adulthood it is thought that genetic factors come to play more of a role in our intelligence during middle and old age and that the importance of the environment dissipates.
Adult development encompasses the changes that occur in biological and psychological domains of human life from the end of adolescence until the end of one's life. Changes occur at the cellular level and are partially explained by biological theories of adult development and aging. Biological changes influence psychological and interpersonal/social developmental changes, which are often described by stage theories of human development. Stage theories typically focus on "age-appropriate" developmental tasks to be achieved at each stage. Erik Erikson and Carl Jung proposed stage theories of human development that encompass the entire life span, and emphasized the potential for positive change very late in life.
Timothy C. Bates is a professor of differential psychology at the University of Edinburgh. His research interests include the genetics of reading and spelling, intelligence, and personality.
Cognitive epidemiology is a field of research that examines the associations between intelligence test scores and health, more specifically morbidity and mortality. Typically, test scores are obtained at an early age, and compared to later morbidity and mortality. In addition to exploring and establishing these associations, cognitive epidemiology seeks to understand causal relationships between intelligence and health outcomes. Researchers in the field argue that intelligence measured at an early age is an important predictor of later health and mortality differences.
The University of Edinburgh School of Philosophy, Psychology and Language Sciences (PPLS) is a school within the College of Humanities and Social Science at the University of Edinburgh. The School was formed in 2002 as a result of administrative restructuring, when several departments of what was then the Faculty of Arts were brought together. The University of Edinburgh's academic foundation is based on three Colleges containing a total of 22 Schools; among these is the School of Philosophy, Psychology, and Language Sciences (PPLS).
The Lothian birth-cohort studies are two ongoing cohort studies which primarily involve research into how childhood intelligence relates to intelligence and health in old age. The Lothian Birth Cohort studies of 1921 and 1936 have, respectively, followed up Lothian-based participants in the Scottish Mental Surveys of 1932 and 1947 in old age. Scottish Mental Survey data has provided a measure of the intelligence of Lothian Birth Cohort participants at age 11, which has enabled the investigation of how childhood intelligence relates to cognition, mental health and physical health in old age.
The following outline is provided as an overview of and topical guide to human intelligence:
Thomas H. Bak is a Polish-British cognitive neuroscientist. He is a researcher at the University of Edinburgh whose work centres on the impact of bilingualism on cognitive functions, bilingualism and cognitive function across the lifespan, cross-linguistic studies of aphasia, and the relationship between language, cognition and culture in neurodegenerative brain diseases. He also works on the design and adaptation of cognitive and motor assessments to different languages and cultures.
Intelligence and personality have traditionally been studied as separate entities in psychology, but more recent work has increasingly challenged this view. An increasing number of studies have recently explored the relationship between intelligence and personality, in particular the Big Five personality traits.
Wendy Johnson is an American differential psychologist and professor of psychology at the University of Edinburgh. She holds the chair in Differential Development in the Department of Psychology and Centre for Cognitive Ageing and Cognitive Epidemiology at the University of Edinburgh.
Heather Clare Whalley is a Scottish scientist. She is a senior research fellow in neuroimaging at the Centre for Clinical Brain Sciences, University of Edinburgh, and is an affiliate member of the Centre for Genomic and Experimental Medicine at the University of Edinburgh. Her main focus of research is on the mechanisms underlying the development of major psychiatric disorders using the latest genomic and neuroimaging approaches.
Michelle Luciano is a Professor at the School of Philosophy, Psychology and Language Sciences at the University of Edinburgh. Her research focuses on the use of twin studies to estimate genetic and environmental contributions to human behavior. She has conducted research on the relationship between Mediterranean diet and brain volume. She was awarded the Visiting Professor Award to visit Trinity College Dublin in June 2019. She was a lead researcher in a study which identified 42 genetic variants associated with dyslexia and that the genetic risk was similar between sexes, this project was in collaboration with researchers from Max Planck Institute for Psycholinguistics, QIMR Berghofer Medical Research Institute, and 23andMe.
