Keith S. Taber
A key part of teaching or communicating science, is about 'making the unfamiliar familiar'.
(Read about 'Making the unfamiliar familiar')
Analogies can be used as pedagogic devices to make the unfamiliar familiar' – that is by suggesting that something (the unfamiliar thing being explained) is somehow like something else (that is already familiar), the unfamiliar can start to become familiar. The analogy functions like a bridge between the known and the unknown. (Note: the idea of a bridge is being used as simile there – another device that can be used to help make the unfamiliar familiar.)
(Read about 'analogies in science')
(Read about 'similes in science')
For an analogy (or simile) to work, the person being taught or communicated with has to already be familiar with the 'source' that act as an analogue for the 'target' being communicated. (If someone did not know what a bridge was, what it is used for, then it would be no help to them to be told that an analogy can function like one! Indeed it would probably just confuse matters.)
An analogy is based on some mapping of structure between two different systems. For example, at one time a common teaching analogy was that the atom was like a tiny solar system. For that to be useful to a learner, they would need to be more familiar with the solar system than the atom. To be used as an effective teaching analogy, the learner would have to understand the relevant parts of the conceptual structure of the solar system idea that were being mapped across to the atom (perhaps a relatively large central mass, the idea of a number of less massive bodies orbiting in some way, a force between the central and peripheral bodies responsible for the centripetal acceleration of the orbiting bodies…).
A person might easily map across irrelevant aspects of the source to the target, perhaps as all the planets are different then all electrons must be different! This might explain why some students assume the force holding the atom together is gravitational!
(Read about 'Understanding Analogous Atomic and Solar Systems')
In teaching science, it is common to use everyday sources as analogues for scientific ideas. But, of course, it is also possible to use scientific ideas as the source to try to explain other target ideas.
Below I reproduce an extract from a recent publication (Taber & Li, 2001). I developed an analogy between enzymatic catalysis (a scientific concept) and scaffolding of learning (an educational or psychological concept), to use is a chapter I co-wrote with Xinyue Li .
(Read about 'Scaffolding learning')
The mapping I had in mind was something like this:
| Aspect | Source (Enzymatic catalysis) | Target (Scaffolding) |
| Process | Chemical reaction | Development of new knowledge/skills |
| Impediment | Large activation energy – barrier far greater than energy available to reactant species | Large learning demand – gap between current capability and mastery of new knowledge/skill exceeds manageable 'learning quantum' |
| Intervention | Addition of enzyme | Mediation by 'teacher' |
| Mechanism | Provides alternative reaction pathway with small energy barriers | Structures learning by modelling activity, and leads learner through small manageable steps |
| Matching | The enzyme 'fits' the reactant molecule and readily binds | A good scaffold matches the learners' current capacity to progress in learning (in the so-called 'ZPD') |
| Degrees of freedom | The binding of the enzyme to a substrate 'guides' the subsequent molecular reconfiguration | The scaffolding guides the steps in the learning process taken by the learner |
Scaffolding Learning as Akin to Enzymatic Catalysis
"Metaphors and analogies should always be considered critically, as the aspects that do not map onto the target they are being used to illustrate can often be as salient and as relevant as the aspects that map positively. Given that, and in the spirit of offering a way to imagine scaffolding (rather than an objective description) we suggest it may be useful to think of scaffolding learning as like the enzymatic catalysis of a chemical process in the body (see Figure 3).
Figure 3. Scaffolding learning can be seen as analogous to enzymatic catalysis (b) which facilitates a reaction with a substantive energy barrier (a).
Some chemical reactions are energetically viable (in chemical terms, exothermic) and so in thermodynamic terms, occur spontaneously. However, sometimes even theoretically viable (so spontaneous) reactions occur at such a slow rate that for all practical purposes there is no reaction. For example, imagine a wooden dining table in a room at 293 K (20˚C) with an atmosphere containing about 21% oxygen – a situation found in many people's homes. The combustion of the table is a viable chemical process [1] and indeed the wood will (theoretically) spontaneously burn in the air. Yet, of course, that does not actually happen. Despite being a thermodynamically viable process, the rate is so slow that an observer would die of old age long before seeing the table burst into flames, unless some external agent actively initiated the process. If parents returned home from an evening out to be told by their teenage children that the smouldering dining table caught alight spontaneously, the parents would be advised to suspect that actually this was not strictly true. Although the process would be energetically favourable, there is a large energy barrier to its initiation (cf. Figure 3, top image). Should sufficient energy be provided to ignite the table, then it is likely to continue to burn vigorously, but without such 'initiation energy' it would be inert.
The process of catalysis allows reactions which are energetically favourable, but which would normally occur at a slow or even negligible (and in the case of our wooden table, effectively zero) rate to occur much more quickly – by offering a new reaction pathway that has a much lower energy barrier (such that this is more readily breached by the normal distribution of particles at the ambient temperature).
In living organisms, a class of catalysts known as enzymes, catalyse reactions. Enzymes tend to be specific to particular reactions and very effective catalysts, so reactions akin to the burning of organic materials (as found in our wooden table) can occur as part of metabolism at body temperature. The second image in Figure 3 represents the same chemical reaction as in the top image (note the same start and finish points) reflecting how an enzyme changes the reaction pathway, but not the overall reaction. Two particular features of this graphical metaphor are that the overall process is broken down into a number of discrete steps, and the 'initiation energy' needed to get the process underway is very much smaller.
This is similar to the mediation of learning trough scaffolding, where a task that is currently beyond the capacity of the learner is broken down into a sequence of smaller steps, more manageable 'learning quanta', and the learner is guided along a learning pathway. The parallels go beyond this. Part of the way that an enzyme functions is that the enzyme molecule's shape is extremely well matched to bind to a target reactant molecule (something reflected in the teaching analogy of the 'lock and key' mechanism of enzymatic action: the enzyme and substrate molecules are said to fit together like a lock and key). This is analogous to how effective scaffolding requires a teacher to design a scaffold that fits the learner's current level of development: that is, her current thinking and skills. Once the substrate molecule is bound to the enzyme molecule, this then triggers a specific reconfiguration: just as a good scaffolding tool suggests to the learner a particular perspective on the subject matter.
Moreover, whereas a free substrate molecule could potentially follow a good many different pathways, once it is bound to the enzyme molecule its 'degrees of freedom' are reduced, so there are then significant constraints on which potential changes are still viable. Most organic chemistry carried out in vitro (in laboratory glassware) is inefficient as there are often many 'side reactions' that lead to unintended products, just as students may readily take away very different interpretations from the same teaching, so the yield of desired product can be low. However in vivo reactions (in living cells), being enzyme-catalysed, tend to give high yields.
The process of enzymatic catalysis therefore makes the preferred pathway much 'easier', offers a guide along the intended route, and channels change to rule out alternative pathways. Digital tools that support teaching to meet curricular aims, such as apps intended to be used by learners to support study, therefore need to offer similar affordances (structuring student learning) and constraints (reducing the degrees of freedom to go 'off track'). Clearly this will rely on design features built into the tool. Here we very briefly discuss two examples."
[1] We avoid the term 'reaction' here, as strictly a chemical reaction occurs between specific substances. Wood is a material composed of a wide range of different compounds, and so the combustion of wood is a process encompassing a medley of concurrent reactions.
(Taber & Li, 2001, pp.55-58)
Work cited:
- Taber, K. S., & Li, X. (2021). The vicarious and the virtual: A Vygotskian perspective on digital learning resources as tools for scaffolding conceptual development. In A. M. Columbus (Ed.), Advances in Psychology Research (Vol. 143, pp. 1-72). New York: Nova. (Download the chapter by clicking this link.)
