Like most aspects of human behavior and cognition, intelligence is a complex trait that is influenced by both genetic and environmental factors. ... These studies suggest that genetic factors underlie about 50 percent of the difference in intelligence among individuals.

What is the role played by genetic factors in intelligence?

Another special genetic feature of intelligence is that its differences are caused by genes that affect cognitive abilities as diverse as, for example, spatial ability, vocabulary, processing speed, executive function and memory.

Does intelligence run in families?

General intelligence definitely runs in the family. Twin studies (on both identical twins and fraternal twins) have found a heritability of IQ between 57% and 73%, and in some cases, even higher. Interestingly, genetic studies have revealed that a child's IQ score is less affected by intelligence genes than an adults.