At the beginning Freud disliked transferential reactions, considering them interferences, without a specific meaning ( like " suggestion" ). In order to distinguish the real therapeutic problems from " transfert " resistance and " suggestion" improvement, he recommended the analist "opaqueness" to his disciples. Then he discovered the specificity of the"transfert" still recommending the analist "opaqueness". Today we want to distinguish the "placebo" effect from the pharmacodynamic effect in a therapeutic drug. But it's the first homogenous and non specific in the general population ?