Interactional expertise is part of a more complex classification of expertise developed by Harry Collins and Robert Evans (both based at Cardiff University). In this initial formulation interactional expertise was part of a threefold classification of substantive expertise that also included ‘no expertise’ and ‘contributory expertise’, by which they meant the expertise needed to contribute fully to all aspects of a domain of activity. Classification The distinction between these three different types of expertise can be illustrated by imagining the experience of a social science researcher approaching a topic for the first time. It is easy to see that, whether the research project is to be about plumbing or physics, most researchers will start from a position of ‘no expertise’ in that area. As the research project proceeds and the social interactions between the researcher and the plumbers or physicists continue, the social researcher will become increasingly knowledgeable about that topic. For example, they will find that they can talk more interestingly about plumbing or physics and ask more pertinent questions about how it works. Eventually, the researcher may even get to the point where they can answer questions about plumbing or physics as though they were a plumber or physicist even though they can’t do plumbing or physics. It is this kind of expertise that Collins and Evans call interactional expertise. The important thing to note about interactional expertise is that the only thing the social researcher can’t do that a practicing plumber or physicist can do is the practical work of actually installing central heating or conducting experiments. It is this difference – the difference between being able to talk like a plumber/physicist and actually do plumbing/physics – that is the difference between interactional expertise (what the researcher has) and contributory expertise (what the plumbers and physicists have). Of course, plumbers and physicists who can talk fluently about their work will have both kinds of expertise. In identifying this separate and distinctive kind of linguistic expertise, the idea of interactional expertise makes a clear break with other theories of expertise, particularly those developed in science and technology studies, which tend to see expertise as a social status granted by others rather than a property of the individual. As discussed in more detail below, the idea of interactional expertise also differs from more traditional phenomenological theories of expertise, in which the embodied expertise of the contributory expert is well-recognised