AQA A A2: Theories of Perceptual Organisation
Those students studying Perception as one of the “topics” in Unit 3 A2 Psychology, will learn about 2 theories of perceptual organisation (Richard Gregory’s top down theory and James Gibson’s bottom up theory). There is clearly much scope here for considering the fascinating world of visual illusions, exploring how we come to see things that are simply not there and what this tells us about how we perceive the world around us. Both Gibson and Gregory have attempted to explain how are perceptual systems are “tricked” by illusions with their theories, so why not start with this to intrigue students and draw them into this area of study.
Visual illusions: free resources
There are many websites that give easy access to static and animated illusions that work well as classroom resources. An episode from BBC 2’s Horizon series included a “red button” interactive experience called “seeing is believing” (linked to a documentary aired Monday 18th October 2010, now available online). This included a number of illusions, explained by a researcher in this field, which would make an invaluable classroom resource because of its interactive nature. You could also have the late Richard Gregory visit your classroom to describe how the size scaling illusion (or Ponzo illusion) actually works in a short video on available on You Tube.
With any new topic it is worth planning a first lesson that introduces the area of study, hints at the different perspectives to be explored and enables students to reveal misconceptions they might hold whilst generating questions they genuinely want to know the answers to. To introduce perception try setting up your classroom – or a bigger space (e.g. drama hall) – in the style of a gallery/exhibition. At various “stands” around the room arrange examples of illusions grouped by themes. Here some ideas for grouping the illusions:
Select some of the well-known illusions, that students are likely to have come across before, such as the Muller-Lyer, the Necker Cube, moving eye illusions and Ames room (follow this link for a nice video explaining the illusion). You could print the illusions as large copies or display them digitally. You might like to include explanations of how they trick the brain or leave students to make their own judgements. The horizon interactive resource could be included at this stand.
Illusions as art
The work of artists such as Escher could be included at this stand. An article in New Scientist entitled “Impossible figures brought to life in virtual worlds” (BY Paul Marks, published online 02/06/2012) includes examples of impossible figures represented in 3D environments by Chinese Computer scientists. The article includes video of the 3D figures which could be played for students to see in this part of the gallery.
Richard Wiseman regularly tweets and blogs about 3D illusions which have come to his attention. Those that include pavement art could be used in the previous section. These links will take you to particularly good posts on his blog: “impossible 3D illusions”; “world’s best 3D art”.
Other sensory illusions: Sound and tactile (haptic) illusions
There is no need to focus solely on visual illusions as there are many examples of illusions of other senses that are worth considering here such as music illusions. New Scientist featured an article about these called “Music special: Five great auditory illusions” (February 2008) and Scientific American also featured an article, with a podcast embedded, focussing on auditory illusions. You could include tactile illusions as an additional example.
Lesson plenary: outcomes
Ask students to discuss what they have seen and experienced as a class in the latter part of the lesson. They could select their favourite illusion or the one that baffled them the most. Students should be asked what these illusions might tell us about how we make sense of the world around us; how do we know what we are seeing, hearing, touching? If students start to talk, spontaneously, about the role our expectations and prior knowledge play, this can be used to introduce the idea of top down and bottom up processing. Many students will simply never have given much thought to how we know what something is but will find the mind boggling nature of the illusions hard to explain without attempting to formulate some kind of theory about how the sensory information comes to be interpreted as something meaningful.