A. untilB. learningC. whenPhrases:A. does not mature 1 about the age of twoB. remember 2to walkC. 3they search through their mental files What's your earliest childhood memory? Can you 4 ? Or talk? The first time you heard thunder or watched a television program? Adults seldom recall events much earlier than the year or so before entering school, just as children younger than three or four rarely retain any specific, personal experiences. A variety of explanations have been proposed by psychologists for this "childhood amnesia" (儿童 失忆症). 0ne argues that the hippocampus, the region of the brain which is responsible for forming memories, 5. But the most popular theory maintains that, since adults do not think like children, they cannot reflect childhood memories. Adults think in words, and their life memories are like stories or narratives—one event follows another as in a novel or film. But 6for early childhood memories to add to this verbal life story, they don't find any that fits the pattern. It's like trying to find a Chinese word in an English dictionary.