forbid
intrusive
experimentation
Such considerations are not extended to non-humans, with the consequence that the neuroanatomy and neurophysiology of non-human, primate visual systems, similar in their capacities to that of humans, are already understood in some detail. For language, however, we have to rely on less controlled methods of investigation, for example, by studying brain-damaged patients who suffer from language disorders. In these circumstances, the extent and precise nature of the damage is not known, a factor which inevitably contributes to the tentativeness of conclusions.