They show correlations between household income and their other measures in study 2 (significant positive correlation with conservatism, insignificant positive

They show correlations between household income and their other measures in study 2 (significant positive correlation with conservatism, insignificant positive correlation with extremism), and between income at 2 ages in study 3 (in both cases there was significant relationship to conservatism and a weaker significant relationship to extremism). I think it's more interesting that they focus on finding their one relationship (between intelligence and extremism) and don't really unpack the relative sizes to other correlations in their own studies. E.g. the link between intelligence and extremism is weaker than the link between intelligence and conservatism (though studies 2 and 3 find _opposite signs_ for this relationship) and is weaker than the link between intelligence and income. So their study is basically consistent with the possibility that some intelligent people earn higher incomes and richer people are likely to be atypically conservative.