On knowing too much to teach...

This post was originally a comment on a comment on this post on another blog, which got a bit out of hand—

'it is hard to see how knowing less about the thing being taught can make you a better teacher of the thing being taught.'

This may well be the case in schools—my experience is limited. But in post-compulsory (further/higher/adult) education, one of the most formative learning experiences I have ever had was probably a conversation with colleagues in the canteen of the (then) Salford Technical College, killing time before the start of evening classes (c. 1970). The leader of the Marketing courses posed the question, 'Can you know too much about a topic to teach it well?'

A great question, and Tom had recently joined the college (why, goodness only knows) directly from a senior position in marketing in the private sector, so he was picking up this teaching stuff from scratch (on a sink or swim basis in those days) but he did bring with him his native perspective on consumer behaviour, which implies a (limited) degree of empathy with them, which he extended to students.

45 years later I don't recall the details, but I do remember that my position then was "no". Obviously the more you know about something the better you can teach it!

I was wrong. As a jack-of-many-subjects (but all of them rather "soft" and vague) I was not yet aware of how little I knew about any of them; so I had not actually come up against the problem, but later on I did get to the stage of knowing too much in a few areas.

There are two main problems with knowing too much;

• One is that of bounding one's own knowledge—confining it to the course curriculum and not wandering off into abstruse detail which serves only to confuse the students. This is a particular problem when teaching introductory courses, when you know that what you are teaching is not exactly wrong, but is drastically over-simplified and does not consider all the exceptions to a rule. The temptation is to explain them, and in so doing to lose sight of the broad picture or rule of thumb which is an essential part of scaffolding the teaching. And there is also the perpetual temptation to show off.

• And then there is the failure to appreciate students' difficulties. This is of course the root of the traditional caricature of the punitive teacher, who really cannot understand why students do not—or, it seems will not—understand. And it is a particular problem in relation to threshold concepts, because as the term suggests, once they have been grasped it is difficult to see how one could have ever done without them. The teacher is forever on the other side of the threshold from the learner, and has to make a conscious effort to grasp the learner's lack of comprehension. But of course there is no point in trying to teach without having passed the threshold(s). This is a variant of the curse of knowledge, so effectively explored by Steven Pinker in his wonderful The Sense of Style (Allen Lane; 2014).

But it is not merely about knowing too much—it is if anything more of a problem in respect of skills, partly because as Reynolds (1965) suggests, habituation makes it difficult even to remember one's first floundering attempts to master a skill.  (The 'Unconscious Competence' stage of the popular model.)

The title of one of my sites is based on Seneca 'Homines dum docent discunt' ('men learn while they teach' Letter VII to Lucilius On Crowds); it is important to be learning in order to be continually reminded of what it is like to be ignorant or incompetent, in order to get alongside our students. Ignorance is a fragile fruit.