This experimental work was aimed at evaluating the internal coherence of reasoning. Several inferential structures of premises have been also typified so that the relationship likely to be established among these variables, and the specific characteristics of the samples involved could be assessed. Population included 50 psychiatric patients, and 50 sound control subjects. Both samples were administered Lopez-Alonso's Test of Reasoning Coherence. From such evaluations, total scores of logical incoherence mistakes as well as inferential structures of premises have been extracted. Results suggest that the psychiatric patients sample lacks a good control on the cognitive reversibility, hence adhering to more atypical structures based on reductionist criteria that give rise to a large number of mistakes coupled to a much more incoherent, and disorganized reasoning pattern.