<P> Mainly focusing on the development of the human mind through the life span, developmental psychology seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age . This may focus on cognitive, affective, moral, social, or neural development . Researchers who study children use a number of unique research methods to make observations in natural settings or to engage them in experimental tasks . Such tasks often resemble specially designed games and activities that are both enjoyable for the child and scientifically useful, and researchers have even devised clever methods to study the mental processes of infants . In addition to studying children, developmental psychologists also study aging and processes throughout the life span, especially at other times of rapid change (such as adolescence and old age). Developmental psychologists draw on the full range of psychological theories to inform their research . </P> <P> All researched psychological traits are influenced by both genes and environment, to varying degrees . These two sources of influence are often confounded in observational research of individuals or families . An example is the transmission of depression from a depressed mother to her offspring . Theory may hold that the offspring, by virtue of having a depressed mother in his or her (the offspring's) environment, is at risk for developing depression . However, risk for depression is also influenced to some extent by genes . The mother may both carry genes that contribute to her depression but will also have passed those genes on to her offspring thus increasing the offspring's risk for depression . Genes and environment in this simple transmission model are completely confounded . Experimental and quasi-experimental behavioral genetic research uses genetic methodologies to disentangle this confound and understand the nature and origins of individual differences in behavior . Traditionally this research has been conducted using twin studies and adoption studies, two designs where genetic and environmental influences can be partially un-confounded . More recently, the availability of microarray molecular genetic or genome sequencing technologies allows researchers to measure participant DNA variation directly, and test whether individual genetic variants within genes are associated with psychological traits and psychopathology through methods including genome - wide association studies . One goal of such research is similar to that in positional cloning and its success in Huntington's: once a causal gene is discovered biological research can be conducted to understand how that gene influences the phenotype . One major result of genetic association studies is the general finding that psychological traits and psychopathology, as well as complex medical diseases, are highly polygenic, where a large number (on the order of hundreds to thousands) of genetic variants, each of small effect, contribute to individual differences in the behavioral trait or propensity to the disorder . Active research continues to understand the genetic and environmental bases of behavior and their interaction . </P> <P> Psychology encompasses many subfields and includes different approaches to the study of mental processes and behavior: </P> <P> Psychological testing has ancient origins, such as examinations for the Chinese civil service dating back to 2200 BC . Written exams began during the Han dynasty (202 BC.--AD . 200). By 1370, the Chinese system required a stratified series of tests, involving essay writing and knowledge of diverse topics . The system was ended in 1906 . In Europe, mental assessment took a more physiological approach, with theories of physiognomy--judgment of character based on the face--described by Aristotle in 4th century BC Greece . Physiognomy remained current through the Enlightenment, and added the doctrine of phrenology: a study of mind and intelligence based on simple assessment of neuroanatomy . </P>

Who said psychology is the science of soul