For example, a person recalls a hill near the home of his childhood, and has the conviction that it was of great height.

On revisiting the place he finds that the eminence is quite insignificant.
How can we account for this?
For one thing, it is to be observed that to his undeveloped childish muscles the climbing to the top meant a considerable expenditure of energy, to be followed by a sense of fatigue.

The man remembers these feelings, and "unconsciously reasoning" by present experience, that is to say, by the amount of walking which would now produce this sense of fatigue, imagines that the height was vastly greater than it really was.

Another reason is, of course, that a wider knowledge of mountains has resulted in a great alteration of the man's standard of height.
From this cause arises a tendency generally to exaggerate the impressions of early life.

Youth is the period of novel effects, when all the world is fresh, and new and striking impressions crowd in thickly on the mind.