Working memory and why teaching science is hard

I think we would all agree, science teaching is hard, but why? What exactly is it that makes science so difficult to teach? I was recently thinking about this question and came across a great paper by A.H. Johnstone entitled “Why is science difficult to learn? Things are seldom what they seem” and suddenly it all made sense. Science teaching is difficult because science is hard to learn.

In the paper there is a fantastic working model to understand how learning takes place that I have adapted below. The model provides a really useful framework to begin thinking about why learning science is especially difficult and considers the interplay between students’ working and long-term memory.

Why is teaching science difficult? Taken from Johnstone, A.H., 1991

Why is learning science hard?

  1. Many scientific concepts cannot be easily experienced as there are no immediate sensory ways to get at the idea. I know what a cat is because I have seen and stroked a cat. But how do you experience natural selection or translation?
  2. Students will perceive and observe in a selective way based upon previous knowledge and expectations stored in long term memory e.g. heavy things sink, light things float
  3. Storage. For many topics nothing can be pulled out from long term memory to match or anchor new ideas to, and so filing these new ideas away in long term memory is difficult
  4. Retrieval. Much of what is retrieved from the long term memory is in fact wrong (misconceptions), or at least not scientifically acceptable,  and so provides the working memory with incompatible information to what is being observed.

With all of the above, confusion can reign and working memory space can become overwhelmed. This is especially the case as teachers jump from observation, to explanation to representation.

So how can science teachers help?

  1. Deal first with the macrolevel and offer explanation in small doses. Start with the concrete and move to the abstract. Context can help.
  2. Make sure practical work is focused on helping students see the intended ‘signal’ and don’t become distracted by the noise
  3. Be wary of discovery based approaches in science – if this isn’t guided students may discover that sugar disappears, heated particles expand and current is used up! It took till 1859 to discover evolution by natural selection.
  4. Avoid doing too much at one time e.g. the simultaneous reading of worksheet instructions whilst using techniques and making observations can overload students’ working memory
Further reading