Early research by washburn suggested that stomach contractions caused hunger sensations. later research showed that the presence of the balloon in washburn's stomach had caused digestive contractions, not hunger contractions. this is an example of the effects of variables on scientific research.

Which of the following selections is least useful for supporting the claim that states intentionally built unequal school systems? question 1 options: the supreme court ruling in plessy v. ferguson (1896) wrote into law that america had two separate societies: one black and one white. it was very clear by the mid-1900s that southern states had expertly built separate educational systems. these schools, however, were never equal. states with laws keeping schools segregated never gave equal amounts of money to their black and white schools. ten years after brown, fewer than 10 percent of southern public schools had integrated. some areas did not comply at all.