A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.

Harry Collins is an expert on experts. At the core of his approach to expertise is what he calls a “periodic table of expertise”, which not only describes a hierarchy of levels of specialist knowledge, but also the ability of individuals possessing these levels of understanding to distinguish levels of expertise in others and how they do so.

The most basic form of knowledge in Collins’ hierarchy is beer-mat knowledge — an ability to recite facts without being able to do anything with them, except perhaps in a game of Trivial Pursuit. With popular understanding — such as you might expect to glean from a show on Discovery Channel — an elementary conception of meaning might allow for rudimentary inferences.

Collins calls the most accomplished form of expertise contributory expertise. Contributory experts have fully internalized both the language and the practice of their discipline, as only by doing so are they able to contribute to their domain of expertise and perform within it.

Collins’ critical insight is the recognition that there is an additional category of specialist expertise — expertise in the language of a specialism in the absence of expertise in its practice. He calls this interactional expertise and it turns out to be central in understanding the practice of science, technology and engineering.

Interactional expertise is the expertise of the technical project manager and the research manager — fully conversant with all the disciplines that contribute to the project’s goals without necessarily being able to contribute to any of them. It is the expertise of the peer-reviewer, the high-end journalist, the scientific adviser. The overwhelming majority of the fruits of scientific endeavour are synthesized, applied and transmitted through the agency of interactional experts.

The concept of interactional expertise teaches us humility. It allows us to recognize that although we might, rightly, consider ourselves experts in all the fields with which we work, it is only the fewest of them where that expertise is contributory. Seeking the support of contributory experts who can perform in those fields is not a sign that we do not possess that expertise ourselves, only that our expertise is interactional and that we recognize our limitations.

Collins’ work also contains a warning. His study of experts’ ability to assess experts clearly concludes that experts only successfully discriminate downwards. Contributory experts can easily recognize the limits of their interactional counterparts, but the converse is not true. Interactional expertise is not sufficient to discriminate between interactional imposters and contributory colleagues. Interactional experts and indeed Disco channel experts are often unable to recognize even the limits of their own expertise, with often disastrous consequences.

Mathematical modelling for business and the business of mathematical modelling. See stochastic.dk/articles for a categorized list of all my articles on medium.

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