Final answer:
Nativists in the era used the data from early IQ tests, which found that northern and western Europeans scored higher than other groups, to support their anti-immigration and discriminatory agendas.
Step-by-step explanation:
Nativists in the era used the data from early IQ tests, which found that northern and western Europeans scored higher than other groups, to support their anti-immigration and discriminatory agendas. They used this information to argue that certain ethnic and racial groups were intellectually superior to others, particularly to discourage immigration from non-Western European countries. This was part of a larger movement called eugenics, which sought to validate the idea of white supremacy and control immigration based on perceived intellectual differences.