Practical: The Fallacy of Induction

@SotonEdThis is the third and final post in a series about the value of practical work in science. In the first post I have suggested that science trainee teachers (and possibly some qualified teachers too), have a tendency to make assumptions about the value, and the learning, associated with practical work in science. In the second post I illustrated this with an example and briefly tackled two questions I think are important: whether or not children enjoying practical work is sufficient justification, and whether or not just doing practical will make them better at it. I left a third question hanging and ask it again now.

Do children learn important science ideas and/or develop their understanding from seeing the theory ‘in the flesh’? Often trainee teachers think that this is self-evident. I’m not convinced.

Some of the most useful work on children’s ideas, and misconceptions in science was completed by Rosalind Driver and colleagues in the 1990s. I think this is an essential resource for all science teachers because of the evidence that knowledge of children’s misconceptions is an important distinguishing feature between more and less effective teachers. Some may find elements of the suggestions for classroom practice overly constructivist but for me, as well as the identification of a whole range of misconceptions, the other really useful idea I have taken from this work is the ‘fallacy of induction’.
The fallacy of induction is the mistaken belief that children, when presented with relevant evidence, for example from practical work, will tend to work out (induce) the appropriate scientific theory.

The problem is that correct scientific theories are often simple when you know them, but are tremendously hard to generate directly from evidence. After all, it took a lot of very skilled scientific thinkers hundreds of years to do this the first time. What’s worse, children inevitably develop naïve theories as they grow up, so in secondary school they are sometimes not just trying to learn correct scientific thinking but are trying to un-learn naïve thinking that serves them perfectly well outside the classroom.

As teachers, we can of course select learning experiences, including practical work, that provide far more scaffolding and direction than Galileo, Copernicus, Newton, Darwin, Lavoisier, Faraday or Wegener were working with but, however well we do this, I think that induction from practical work, or other activities, is doomed to failure.

For conceptually straightforward science, where there are no misconceptions to overcome, I think that, as a science teacher, we can clearly see how the correct scientific principle follows from the practical observations and it is very easy to assume this will be apparent to the learners too. For the teacher, the scientific principle already exists as a complete and correct schema (like a mind map) in their long-term memory, and they know which features of the practical are relevant, so making this match is relatively easy. For the learner this is not the case. They just don’t have enough of the necessary knowledge chunked in long-term memory to manage the cognitive load – they can’t see the wood for the trees. Like many cognitive load problems, it may be possible to scaffold or adapt the activity sufficiently to allow children to see the wood, but you have to question whether a forest is the right starting place, or whether a nice piece of rough sawn timber from B&Q might be a better option.

Where there are misconceptions, Driver and others have suggested that cognitive conflict, created by exposure to direct evidence that the existing ideas are untenable, will help to resolve the problem. That was certainly my thinking for many years. It seems obvious that, when presented with evidence that is in conflict with their misconceptions, learners will tend to respond by correcting their ideas (their mental representations or schemas). What actually seems to happen a lot of the time is that they ignore, fail to focus on, or distort the evidence, so that their naïve theory survives and may even be reinforced. This explains why so many intelligent people stuck with Aristotle’s ideas about force and motion for a thousand years despite blatant evidence to the contrary.

The ideas of Daniel Kahneman and others help to explain why people have an overwhelming tendency to respond in this way. David Didau in his #WrongBook is also very good on the reasons why our response to contradictory evidence tends to be irrational.

My personal experience is that I have eventually learned the situations where my quick thinking will be wrong and I need to over-write with the correct scientific idea. For something like weight and mass I can pretty much do this automatically but with something more taxing like the tendency to see speed and mistakenly think as if force and acceleration behave in the same way, the best I can do is stop myself and know that I need to think very hard and apply Newton’s Laws with great care.

I don’t think typical practical work ever produces enough clarity in either the results or the conclusions to even begin to address these stubborn misconceptions. I love asking hinge questions, like the Veritasium videos, that throw up misconceptions, but the next step is to tackle the problem head on. I don’t think there are many situations where children can discover scientific principles directly through practical work and I think it even less likely that misconceptions can be effectively challenged and addressed.

So, what role does that leave for practical work in teaching science? I think, if you’ve read this far, you might be thinking there isn’t much practical work in my science teaching, and that perhaps the children taught by my @SotonEd trainee teachers aren’t getting much either, and what little they are getting is restricted to training in purely practical skills – accurate measuring, and manipulation of equipment. Not so! For me, practical work is terrific for the stage beyond basic theoretical knowledge, for three reasons:

Science is stuffed with abstract concepts and there is good evidence that concrete representations help children to understand these abstract concepts. I think sometimes physical models are more useful but practical work can often play this role. For example, you can find a good, clear explanation (with diagrams and perhaps photographs) of chromatography in any textbook but I think the actual physical process of separating out ‘black’ ink colours makes a big difference to children’s grasp of what this really looks like, and the time scale – that painfully slow diffusion – over which it happens.

Secondly, when new knowledge is acquired it will be very fixed to the original context. Deeper understanding comes from making this knowledge more flexible and filtering out the key points from the peripheral detail. Practical work provides an excellent additional level of complexity through which the scientific principle can be seen. Another way to think of this is that children often need to encounter the same idea in several different ways before it sticks; again, a practical can provide this.

Finally, there is something joyful about seeing abstract theory writ large (or often actually quite small) in the fabric of the universe. Science differs from other subjects because it is humankind’s ultimate attempt to describe, and perhaps even understand, the physical world around us. As science teachers, we need to be careful not to think that children see practical work the way we do, but if we ever lose the joy then it’s time to do something else.

Driver R. (1994). The fallacy of induction in science teaching. Chapter 3 in Levinson, R. ed. (1994) Teaching Science. London: Routledge

Nuthall G. (2007) The Hidden Lives of Learners. Wellington: NZCER Press

Pashler H., Bain P.M., Bottge B.A., Graesser A., Koedinger K, McDaniel M and Metcalfe J. (2007) Organizing Instruction and Study to Improve Student Learning: IES Practice Guide. Washington, DC: National Center for Education Research, Institute of Education Sciences, U.S. Department of Education

Sadler P.M. and Sonnert G (2016) Understanding Misconceptions: Teaching and Learning in Middle School Physical Science. American Educator. 2016 (Spring)

Shtulman A. and Valcarcel J. (2012) Scientific knowledge suppresses but does not supplant earlier intuitions. Cognition. 124(2) pp.209-215

Thorn C.J., Bissinger K., Thorn S. and Bogner F.X. (2016) “Trees Live on Soil and Sunshine!”: Coexistence of Scientific and Alternative Conception of Tree Assimilation. PLoS ONE. 11(1)

Willingham D. (2002) Inflexible Knowledge: The First Step to Expertise. American Educator. 2002 (Winter)


2 thoughts on “Practical: The Fallacy of Induction

  1. Could I recommend a revisiting of the CLIS (Driver) materials (Energy, Particles, Plant nutrition : approaches to teaching ) ( to see the range of purposes for practical work in the teaching sequences. Induction of scientific concepts was not one of planned purposes, and I am not sure what has given rise to the view amongst (trainee) teachers that this is a role for school practical work.

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