[23][24] Adults and children with the DRD4 7-repeat polymorphism show variations in auditory-evoked gamma oscillations, which may be related to attention processing.

[25][26] The frequency of the alleles varies greatly between populations, e.g., the 7-repeat version has high incidence in America and low in Asia.

[27] In 1999 Chen and colleagues[29] observed that populations who migrated farther in the past 30,000 to 1,000 years ago had a higher frequency of 7R/long alleles.

Results are consistent with novelty-seeking behavior being a complex trait associated with many genes, and the variance attributable to DRD4 by itself being very small.

[39][clarification needed] Several studies have shown that agonists that activate the D4 receptor increase working memory performance and fear acquisition in monkeys and rodents according to a U-shaped dose response curve.

[43][44] Gamma oscillations, which may be correlated with cognitive processing, can be increased by D4R agonists, but are not significantly reduced by D4R antagonists.

[39] Michael Connelly’s 2020 crime novel Fair Warning (ISBN 978-0-316-53942-5) revolves around a serial killer who uses DNA profiles obtained on the Dark Web to target female victims, specifically those whose DRD4 profiles allegedly make them more susceptible to risk taking and sexual promiscuity.