Models used in Science are generally visual in nature. It seems fair to say that the representation of a 3D object with a 2D diagram is something that most sighted students will understand. Similarly a student without a visual impairment will be able to scan and track an animation which even for partially sighted students could move too quickly on the screen.
When joining a school for visually impaired I considered the fact that my Powerpoints and animations were now practically redundant for most of the children who I teach. This regularly led me to construct a quick tactile model in place of an animation or when I would otherwise draw a quick diagram on the board. Making such models requires a certain level of creativity and quick thinking, but they can be made very quickly if given a box of materials to choose from. Having now made a good number of models I am almost certain that they have helped students to understand how a model represents the concept or component and how in turn the model relates to a tactile graphic.
Knitted Digestive System
The knitted digestive system is a good example of a tactile model and the student can be led towards the relevant tactile graphic, with direct references between the two throughout. Click here to see models of the digestive system from Load2Learn. (Registration is required, although it is free.)
Villi Using Tactile Model
When we reach the small intestine another model made from a bath mat can be used to demonstrate the finger-like projections called the villi. Students are likely to have to learn that it is thanks to the villi that the surfacearea is increased and therefore maximum absorption can take place. At this point teachers often talk about the mathematical principles of surface area. However, as the principle of absorption is the most important point here I take two 10cm x 10cm swatches of the bath mat fabric. I cut off the projections from one and leave the other intact. I dunk them both in water and squeeze out 3 times more water from the original one compared to the shaved one. This demonstrates the point perfectly within very little time.
Cardiac Cycle Using Wikki-Stix
Another model demonstrates the structure of the heart and cardiac cycle. Wikki-Stix are stuck to a white tray and blood is represented by red beads (some loose and some linked). The Wikki-Stix can be adjusted to show the opening and closing of valves.
Whilst handling the models it is crucial to learning that all components are referred to using the correct terminology and students will then acquire the appropriate language associated with their tactile memory of the model. Students without a visual impairment are likely to be able to see a diagram and recognise it as symbolic of the model, concept or object. However a blind child may need a diagram described to them each time they look at it, particularly if it is not the same as one seen before. A Pen Friend from RNIB can help a student at this point. An audio description of the image can be recorded onto a sticky label placed on the diagram. When the Pen Friend is placed onto the label it will play the recorded audio description of the diagram back to the student. Our students have recorded information about each of the elements of the periodic table and other students are able to use the Pen Friend to listen to these recordings.
Lucia Hasty (2008) suggests that sighted students will look at the whole picture then focus on its parts. For a blind student using a tactile graphic they observe the picture in entirely the other way. They will observe the various parts and construct the whole image (Learn more in this webcast about Teaching Tactile Graphics.) I feel that using tactile models in the way that I have mentioned will ultimately help students to make sense of a diagram in relation to the object or concept.