Sigmund Freud skriver til sin venn Wilhelm Fliess i Berlin (her gjengitt i engelsk oversettelse -- originalen er på tysk):
"The early period before the age of 1 1/2 years is becoming even more significant. I am inclined to distinguish several periods even within it. Thus I was able to trace back, with certainty, a hysteria that developed in the context of a periodic mild depression to a seduction, which occurred for the first time at 11 months and [I could] hear again the words that were exchanged between the two adults at that time! It is as though it comes from a phonograph.