Despite support for evolutionary theories relating to an innate origin of racism, various studies have suggested racism is associated with lower intelligence and less diverse peer groups during childhood. A neuroimaging study on amygdala activity during racial matching activities found increased activity to be associated with adolescent age as well as less racially diverse peer groups, which the author conclude suggest a learned aspect of racism. A meta analysis of neuroimaging studies found amygdala activity correlated to increased scores on implicit measures of racial bias. It was also argued amygdala activity in response to racial stimuli represents increased threat perception rather than the traditional theory of the amygdala activity represented ingroup-outgroup processing. Racism has also been associated with lower childhood IQ in an analysis of 15,000 people in the UK.