The correct answer is D. decreases . . . improves. McGeoch & McDonald (1931) tested their hypothesis that words with the same meaning would be more prone to interference than the unrelated information. In the experiment participants were given a list of words that they practised until they fully memorized it. They were then given another list to remember. The second lists varied, so the second list was totally unrelated. Others were given a second list that contained synonyms of the first. When asked to recall the first list, those who had learned synonyms in the second list had a weaker result and learning unrelated information in the second list produced less impairment. The conclusion was that the interference was most likely to occur with the similar material.
