I've just read a very interesting book about memory. There are fascinating chapters about children's first memories (and why we don't remember anything from our first three years), also about near-death 'I saw my life flash before me' experiences, about what is behind deja vu experiences, about how people reminisce more as they get older and about why life seems to speed up as we get older.

Life does seem to speed up as we get older and most people accept the explanation that "the apparent length of a period in somebody's life is related to the length of his life. A child aged ten would experience one year as a tenth of his life, a man of fifty as a fiftieth."

But this is not really an explanation for why we experience it this way. The author quotes William James, who has a better explanation. He says the shrinking years are due to "the monotony of the memory's content, and the consequent simplification of the backward-glancing view. In youth we may have an absolutely new experience every hour of the day. Apprehension is vivid, the retentiveness strong, and our recollections of that time, like those of a time spent in rapid and interesting travel, are of something intricate, multitudinous and long-drawn out. But as each passing year converts some of this experience into automatic routine which we hardly note at all, the days and the weeks smooth themselves out in recollection to contentless units, and the years grow hollow and collapse."