In Figure 2, Ebbinghaus ran a series of 92 tests. In each test, he gave the subject 13 random syllables and let the subject memorize them. Then he gave the subject another 13 random syllables, and so on, for 8 times in total. Each time, he noted down how many seconds it took for the subject to memorize the 13 syllables. He then took the average over the 92 tests, and graphed it. He found that it takes on average 105 seconds to memorize the first 13 syllables, then 140 seconds to memorize the second 13 syllables, and then 142, 146, 146, 148, 144, 140.

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