J. Allan Hobson, professor of psychiatry at Harvard medical school, tried to
prove that, in fact, this theory was not built on scientific evidences. First
he said that Freud worked principally with his own oneiric material. He did not
really try to reproduce his experiments on some random subjects, so he did not
respect the scientific thinking principle number 4: replicability. Second he spoke about Karl Popper's assertion that all Freud's work was untestable. Indeed we cannot either prove nor disprove what the Austrian psychoanalyst thought about the interpretation of dreams. And this is not compatible with the third scientific principle: falsifiability. A claim that cannot be disprove by a study cannot be considered as a scientific theory.
Allan Hobson also criticized Freud's claim which said that our unconscious is
mainly composed of our unexorcised infantile wishes, because there is no
evidence than children before age 3 have a declarative memory. And we also now
know that the unconscious is cognitive, which may prove that the unconscious is
not mainly repressed, as Freud said.
Allan Hobson and Robert McCarley proposed an alternative theory in the 1970s:
the activation-synthesis theory. For them dreams reflect brain activation in
sleep, and not unconscious repressed wishes. And they think that the
incoherence and illogicality we can experience during dreams are due to the
chaotic informations received by the forebrain, and not to a symbolic latent
content we should decrypt.
As we saw the Freud's dream protection theory is not supported by scientific
studies, contrary to the Hobson and McCarley's activation-synthesis theory. And
we can conclude that Freud was more a philosopher than a real scientist. But
the beginning of the 20th century was an other era for the field of psychology.
Psychology: From Inquiry to Understanding, Scott Lilienfield (2011)