Like many aspects of human cognition and behavior, intelligence is a trait that is influenced by both environmental and genetic factors. Generally, Intelligence is difficult to study because it can be measured and defined in various ways. Many definitions of intelligence take account the ability to adapt to changing environment and to learn from experiences. Elements of intelligence are the ability to plan, reason, think abstractly, understand complex ideas and solve problems.
Researchers have carried out many studies to identify genes that determine the level of intelligence. Most of these studies have focused on differences and similarities in IQ within relatives, mainly looking at twins and adopted children. These studies have found that genes underlie about a half of the difference in intelligence among people.
Other studies have explored variations across the whole genomes of several people to determine if there are any particular areas of the genomes that are related to IQ. Although these studies have not conclusively found any genes that influence intelligence, it is likely that numerous genes are involved, each making a small contribution to the intelligence of an individual.
Intelligence is also influenced by environment. Parenting, nutrition, availability of learning resources and education, among others, all influence intelligence.