We are interested in the validation of a cognitive theory of human communication, grounded in a speech acts perspective. The theory we refer to is outlined, and a number of predictions are drawn from it. We report a series of protocols administered to 13 brain-injured subjects and to a comparable control group. The tasks included direct and indirect speech acts, irony, deceits, failures of communication, and theory of mind inferences. All the predicted trends of difficulty are consistently verified; in particular, difficulty increases from direct/indirect speech acts to irony, from irony to deceits, and from deceits to failure recovery. This trend symmetrically shows both in the successful situation and in the failure situation. Further, failure situations prove more difficult to handle than the relevant successful situation. In sharp contrast with previous literature, there is no difference between the subjects' comprehension of direct and indirect speech acts. The results are discussed in the light of our theoretical approach.