When we learn any new thing, like French or golf or speaking in public, we never advance steadily. We do not improve gradually. We do it by waves, by abrupt starts and sudden stops. Then we remain stationary a time, or we may even slip back and lose some of the ground we have previously gained. These periods of stagnation, or retrogression, are well known by all psychologists; they have been named “plateaus in the curve of learning.”
