Scientific papers and research are subject to peer review but, in most cases, the reviewers will be drawn from cognate or related fields. This is particularly common in research funding decisions, where the likelihood of an application being reviewed by non-specialists increases with the amount of money involved. Even in the case of smaller awards, and of peer reviewed papers, it is still often the case that reviewers will have contributory expertise in a different narrowly defined specialism to that of the author being reviewed. If interactional expertise did not exist, then justifying peer review would be difficult. If, however, reviewers can have expertise by virtue of their interaction with a range of cognate scientists, then the process of peer review seems reasonable.