Around 120 years ago, Ebbinghaus began his study of memory. He (36) ____ on studying how quickly the human mind can remember (37) ____. One result of his research is known as the total time hypothesis (假设), which simply means the amount you learn (38) ____ on the time you spend trying to learn it. This can be taken as our first rule of learning. Although it is usually true that studying for four hours is better than studying for one, there is the question of how we should use the four hours. For example, is it better to study for four hours (39) ____ or to study for one hour a day for four days in a (40) ____? The answer, as you may have (41) ____, is that it is better to spread out the study times. This (42) ____, through which too can learn more (43) ____ by dividing our practice time, is known as the distribution of practice effect. Thus, (44) __________________________________________. But we’re not finished yet. We haven’t considered how we should study over very short periods of time. (45) __________________________________________. Should you look at the same word in rapid succession, or look at the word and then have some delay before you look at it again? (46) __________________________________________.