Standing on the threshold
Jonathan Haslam, Director, IEE
One of the most interesting aspects of the Research Schools Network were the regular “deep dives” into evidence that we held with Research Schools, where we got together and discussed the evidence supporting particular approaches. And these were most interesting when led by Research Schools themselves, bringing areas of research that were of interest to them. Because, as we have outlined in our Engaging with Evidence guide, there are many different kinds of “evidence” out there, of different kinds and quality. It can all be useful to practice, but the challenge is in getting a clear understanding of how it can be useful, and the extent to which this use is “proven” or evaluated.
A perfect example of this, I think, can be found with “threshold concepts”.
The theory of threshold concepts developed at the end of the last century in relation to the teaching of economics undergraduates. Erik Meyer and Ray Land, in their 2003 chapter on the theory, describe the features of a threshold concept:
“… a threshold concept, across a range of subject contexts, is likely to be:
a) Transformative, in that, once understood, its potential effect on student learning and behaviour, is to occasion a significant shift in the perception of a subject, or part thereof. In certain powerful instances, such as the comprehension of specific
b) Probably irreversible, in that the change of perspective occasioned by acquisition of a threshold concept is unlikely to be forgotten, or will be unlearned only by considerable effort.
c ) Integrative; that is, it exposes the previously hidden interrelatedness of something.
d) Possibly often (though not necessarily always) bounded in that any conceptual space will have terminal frontiers, bordering with thresholds into new conceptual areas.
e) Potentially (and possibly inherently) troublesome.”
(The emphases are mine, and I will come back to them in a moment.)
I can understand that threshold concepts are a very seductive theory. There is something inherently pleasing about the notion that, on the way to becoming an expert in something, there are certain transformative concepts that one must master in order to proceed. These concepts turn your world upside down, are real “wow” moments, and you never see things in the same way again. From my own, long-ago study of biology, I can see that the theory of evolution might fit into this, and in other fields, ideas such as Marxism, post-modernism, critical theory, and quantum theory. Experts in a particular subject are likely to rate these transformative concepts highly, because they help to define the subject they love, and make it special. Though I would not class myself as an expert, I would argue that engaging with research evidence has been transformative for me, because I am no longer able to take facts on face value, but instead, rather tediously, want to know what the evidence is behind particular claims.
I can see that thinking about threshold concepts might be helpful when teaching students (of various ages). What are the key concepts that students need to master in order to proceed in a subject, and what misunderstandings might they encounter along the way? That seems to be a useful thing to think about.
My problem is, though, that beyond that, I don’t see that threshold concepts are a particularly useful theory. For me, if threshold concepts are “a thing” then the theory ought to present us with hypotheses that can be tested. Is the theory of evolution a threshold concept, and if it is, how can we prove this? Knowing that something is a threshold concept should lead to a change in the teaching of that concept, that probably involves more time and effort (because a threshold concept is troublesome) but is, presumably, worth that time and effort (because a threshold concept is transformational). Perhaps this would involve a particular framework for teaching a threshold concept, and appropriate (and more in-depth) assessments to check for student understanding. Identifying threshold concepts within subjects would be important, and would need to be fairly rigorous, because these concepts are important but “costly”, so we need to make sure that we have the correct concepts identified.
But this path fails at the first step, in my view. Because, to go back to my earlier emphases, the characteristics of a threshold concept are hedged with vagueness – “likely”, “probably”, “possibly”, etc – so that defining a threshold concept with any confidence is, well, pretty unlikely. This seems to be borne out in the literature. Hundreds of articles have been written about threshold concepts, and, though I can’t claim to have done more than a cursory search, I can’t see that anyone has progressed very far along this path.
These criticisms are neatly summed up in an article by Barry and Littlewood in 2017:
“None of Meyer and Land’s criteria are absolute, and different disciplines and authors seem to emphasize particular areas over others … The questions can be reasonably asked, for example, of why a threshold concept is different than any other key or core concept with such loose definitions, how is transformation measured and how much is enough, or are threshold concepts the same for everyone—ie, is this some externally defined phenomenon or actually an individual internal process? Such questions will need to be addressed with serious scholarship in the further development of practices and theory.”
So where does this place threshold concepts in the context of evidence use in schools? Personally, I like my theories to generate testable hypotheses, and I’m not sure that the theory of threshold concepts has been shown to do that yet (or will ever be able to without refinement). But it is an interesting idea, which educators (particularly in higher education, but also in schools) have found useful as a way of reflecting on how they teach their subject and deepening their own professional thinking. Not everything of value needs to be robustly evidenced through randomised controlled trials. But at the same time, if its value is that difficult to identify, it probably isn’t huge. It reminds me of the description of Earth in the Hitchhiker’s Guide to the Galaxy, which, after some editorial challenge, ended up as “mostly harmless”.