The Interpretation of Dreams by Sigmund Freud Chapter 8 Page 47

support the view that these processes designated “incorrect” are really not falsifications of the normal defective thinking, but the modes of activity of the psychic apparatus when freed from inhibition. Thus we see that the transference of the foreconscious excitement to the motility takes place according to the same processes, and that the connection of the foreconscious presentations with words readily manifest the same displacements and mixtures which are ascribed to inattention.

Finally, I should like to adduce proof that an increase of work necessarily results from the inhibition of these primary courses from the fact that we gain a comical effect, a surplus to be discharged through laughter, if we allow these streams of thought to come to consciousness.