Empirical investigations provide insights into the function of dreams, the effects of events on the day before the dream, so-called day residues, the importance of early childhood experiences in the context of dreams, and Freud's theory of partial wish-fulfilment in dreams. In contrast to more recent assumptions about dream content that came about by chance, there is a clear connection between the dream content and the personality of the dreamer. Another section deals with the - difficult - empirical examination of Freud's theory of mistakes. The method of experimental induction of linguistic errors has led to clear evidence of the influence of unconscious motives on the error. With a completely different methodology, a connection between unconscious motivation and fatal car accidents could also be empirically supported.