Final answer:
The American Protective Association was a nativist group founded in 1887 with the aim of limiting the influence of Catholics and reducing immigration from Catholic countries into the U.S.
Step-by-step explanation:
The primary purpose of the American Protective Association (APA), which was founded in 1887, was to restrict and reduce the influence of Catholics in the United States. The organization was a nativist group that reflected the anti-Catholic and anti-immigrant sentiment prevalent in America during the late 19th century. Although not mentioned in the provided references, the APA campaigned for the hiring of only Protestant individuals for public office and attempted to reduce the influx of immigrants from Catholic countries. It did not, however, have connections with the psychological or sociological associations mentioned in the information provided.