Seeing and Believing

It has long been realised that the human eye is not perfect and also that, given a little visual prompting, the brain is easily confused or fooled.

Optical illusions have provided art and entertainment for centuries, from at least the time of the ancient Greeks to the present day in recent times scientists have come to understand why many of these illusions work. Some are still the subject of study and debate.

In today's edition of The Mercury is the second magazine in the Human Body Series, which focuses on The Brain. Plus, Learning has published a double-page colour spread on Optical Illusions.

Activities:

• Name some of the things in everyday life that depend on some kind of optical illusion and explain how the illusions work.

• "The human eye is a marvel of nature." Use this sentence as the basis for a class discussion or debate.

• Conduct your own optical illusion experiments, such as looking at the moon and using a coin to measure its width at the horizon and up in the sky, or creating a mirage.

• You are a magician specializing in optical illusions. Design your new show, the tricks you will perform, venues, your newspaper advertisements and a publicity stunt.

• Make one of your own optical illusions based on something you have seen or read on the Learning graphic.

Eye Tricks - Your brain can't always interpret what your eyes see.

• Merging Pictures - Cut two pictures from The Mercury. Paste these 5cm apart. Move your nose to the middle of the picture and see how one picture seems to engulf the other. Write a headline for the new picture that you see.

• Blind Spot - Draw a magician on the left of the page and a small rabbit 10cm tot he right. Hold the page at an arm's length. Close your left eye and look at the magician. Slowly bring the page towards you until the rabbit disappears. You have found your right eye's blind spot. List the activities that can be affected by blind spots and describe how we compensate.

• Opposite Colours - Cut a picture out of yellow paper. Paste this onto black paper. State at the yellow image for 30 seconds. Then look at a sheet of white paper. Experiment with other colours. Write your results as if for a scientific journal.

• Spinning Pictures - Cut 2 related pictures from the newspaper, for example a head and a body. Paste them on either side of a cardboard disc. Attach string to opposite ends of the disc, twist the disc and string, the pull the string to spin the disc. Describe the similarities between this effect and a film.

• Holey Hand - Hold a tube in your left hand and look through it with both eyes open. Put your right hand against the side and slide it towards you. Draw a cartoon demonstrating this experiment with a comic caption.

Moving Pictures

• Make a flick book, Draw a stick figure in the corner of a booklet. Continue to draw the same figure in the corner of each page, but changing it slightly each time. Flick through the book and your brain will see a changing image rather than separate pictures.

• Use the TV Guide and the entertainment pages to identify movies that have special effects. Make an advertisement for one, emphasizing this aspect.

Websites

Eyetricks.com
www.eyetricks.com
Although a lot of these sights seem to carry much the same stock illusions, this one has just that little bit extra, including experiments that you can do and there is even a page where you can generate your own stereograms.

Sandlot Science.com
www.sandlotscience.com
There are so many interesting things about perception and optical illusions on this site that it is hard to know where to start. This is simply the best thing there is on the web, although some of the illusions make take a while to load, while others will require plug-ins.

Grand Illusions.
www.grand-illusions.com
Some great illusions including magic tricks, with stuff you can try.

Books

Optical Illusion Experiments

By Michael A. DiSpezio.
This book not only shows you how you can create some of your own optical illusions but it also explains the reasons why funny things happen to your eyes and your brain. (Sterling Publishing, distributed by Capricorn Link Australia)

Optical Illusion Magic

By Michael A. DiSpezio.
Rather than just present loads of optical illusions and make your head spin the author of this book gives reasons why these illusions happen. (Sterling Publishing)

Eye Popping Optical Illusions

By Michael A. DiSpezio.
More great optical illusions and their explanations. (Sterling Publishing)

Senses: Seeing

By Karen Hartley, Chris Macro & Philip Taylor
An exploration of the sense of sight, using photographs, simple text, activities and diagrams. The book covers the anatomy of the sense organs and how sight works; what this sense is used for; information about what happens when something goes wrong with the senses; and further reading. (Heinemann Library)

Magic In Art

By Alexander Sturgis
This title covers such things as trompe l'oeil, diminishing perspective and vanishing points, the work of Escher, anamorphosis, the colour 'tricks' of pointillism and op-art and the now-you-see-it-now-you-don't of the 'two faces or one vase?'. (Heinemann Library)

How Our Bodies Work: How Do Our Eyes See?

By Carol Ballard
Explores the human eye and its ability to provide information about the world. It looks at how light travels through the eye and where in the eye images are seen. Two activities are included to explain how we see in the dark and why two eyes are needed to judge distance and shape. (Hodder & Stoughton Childrens Division)