For most of the 20th century, IQ scores rose globally in what researchers call the Flynn effect, but this trend has reversed in several wealthy nations including Norway, Denmark, and Finland since the 1990s. Genetic factors and immigration have been ruled out as explanations, leaving researchers puzzled about which environmental factors—such as education changes, reading habits, or attention spans—might account for the decline.
Neuroscientist Sergiu Pasca's team at Stanford implanted human cortical organoids into genetically modified mice, creating animals with brains containing millions of human neurons integrated with mouse brain tissue. This breakthrough allows researchers to study human brain cells at the molecular and cellular level in living organisms for the first time, potentially leading to new treatments for autism, schizophrenia, cerebral palsy, and dementia.
A research study using whole-exome sequencing identified 36 large-effect risk genes associated with obsessive-compulsive disorder and chronic tic disorder. The findings may advance understanding of genetic factors underlying these neuropsychiatric conditions.
The article discusses cross-adoption studies as a method to disentangle genetic and cultural contributions to group differences in IQ and academic achievement, noting that East Asian adoptees in Western countries perform better on cognitive measures than reference populations, suggesting potential genetic factors alongside environmental influences.