from "Telling More Than We Can Know: Verbal Reports on Mental Processes" by Richard E. Nisbett and Timothy DeCamp Wilson, Psychological Review Vol.84, No.3, May 1977, pp. 231-259.

In Maiers's (1931) classic experiment, two cords were hung from the ceiling of a laboratory strewn with many objects such as poles, ringstands, pliers, and extension cords.  The subject was told his task was to tie the two ends of the cords together.  The problem in doing so was that the cords were placed far enough apart that the subject could not, while holding onto one cord, reach the other.  Three of the possible solutions, such as tying an extension cord to one of the ceiling cords came easily to Maier's subjects.  After each solution, Maier told his subjects, "Now do it a different way."  One of the solutions was much more difficult than the others, and most subjects could not discover it on their own.  After the subject had been stumped for several minutes, Maier, who had been wandering around the room, causually put one of the cords in motion.  Then, typically within 45 seconds of this cue, the subject picked up a weight, tied it to the end of one of the cords, set it swinging like a pendulum, ran to the other cord, grabbed it, and waited for the first cord to swing close enough that it could be seized.  Immediately, thereafter, Meire asked the subject to tell about his experience of getting the idea of a pendulum.  The question elicited such answers as "It just dawned on me."  "It was the only thing left."  "I just realized the cord would swing if I attached a weight to it."  . . . Maier was able to establish that one particular cue -- twirling a weight on a cord -- was a useless hint, that is subjects were not aided in solving the problem by exposure to this cue.  For some subjects this useless cue was presented prior to the genuinely helpful cue.  All of these subjects reported that the useless cue had been helpful and denited that the critical cue had played any role in their solution.  (240-241)

In order to test subject ability to report influences on their associative behavior, we had 81 male introductory psychology students memorize a list of word pairs.  Some of these word pairs were intended to generate associative processes that would elicit certain target words in a word association task to be performed at a later point in the experiment.  For example, subjects memorized theh word pair "ocean-moon" with the expectation that when they were later asked to name a detergent, they would be more likely to give the target "Tide" than would subjects who had not previously been exposed to the word pairs.  . . .  The average effect of the semantic cuing was to double the frequency of the target responses from 10% to 20% (p<.001).  Immediately following the word association task, subjects were asked in open-ended form why they thought they had given each of their responses in the word association task.  Despite the fact that nearly all subjects could recall nearly all of the words pairs, subjects almost never mentioned a word pair cue as a reason for giving a particular target response.  Instead subjects focused on some distinctive feature of the target ("Tide is the best-known detergent"), some personal meaning of it ("My mother uses tide"), or an affective reaction to it ("I like the Tide box").  (243)