Try this: Corner of your eye

When you look straight ahead, you can see things that aren't directly in front of you. This is called peripheral vision. We are going to check and see how wide you and a friend can see movement, colour and detail.

You will need

• Another person.
• A small piece of paper with writing on it.
• Smarties, M&Ms or similar coloured chocolate buttons. You could also try some construction blocks with the same shape but different colours.
• A table and chair
• Some objects to use as markers. You may be able to use the chocolate buttons.

What to do

First of all, make sure your table is clean and dry. You will want to eat some of your equipment later.

We will use the same basic method to check how far out you and your friend can see movement, colour or detail. To check how far out your friend can see movement:

Checking out my peripheral vision, with the help of Val Leitch*, our Researching with Scientists Officer. I am staring straight at the white plastic lump on the table in front of me. I can see movement out to the yellow line, colour out to the red line and I can only see enough detail to read out to the blue line.

* Val is on secondment from the ACT Department of Education and Community Services to work on a project linking ACT government schools and cutting edge research scientists.

1. Have your friend sit or kneel so their eyes are at the edge of the table. Have them close their left eye and put a marker on the table about a half a metre or so in front of their right eye. They need to stare at this marker and not look away.
2. Hold your hand about 20 centimetres behind their head.
3. Start to wiggle your fingers.
4. With your fingers still wiggling, start to move your hand around to the person's right and then in front of them. Keep your hand at the same level and stay about 20 centimetres away from their head.
5. The moment they say they can see your hand moving, stop and mark the spot.

To check how far out they can see colour, do the same thing with a chocolate button held between two of your fingers. Try to use a bright colour. Move it around until the person kneeling can tell you what colour it is.

To see how wide they can see detail, do the same thing with the bit of paper with writing on it. Move it around until the person kneeling can read the writing. You will probably find you get almost in front of them before they can read it.

Once you have checked all three, you can try it again with the left eye. Then you should swap and check out how wide you can see objects.

I found that I could see fingers moving at about 85 degrees from centre, I could identify the colour out to about 60 degrees and I could only read out to about 10 degrees.

The reason you get different angles has to do with how the eye is put together. We can see because light comes in through the pupil (the black spot in the centre of your eye) and is focussed on the inside of the back of our eye. This area is called the retina and it is covered in light sensors. These sensors detect the light and send a message to your brain.

There are two different types of light sensors in our eyes, which are named after their shape. Cones let us see colours and are good at seeing detail. Rods are more sensitive than cones, but they can only see in black and white. They are good for seeing size, shape and brightness.

The rods and cones aren't spread out evenly inside our eyes.

• When we look straight at something, the light from it goes to a part of our eye called the fovea. The fovea has lots of cones packed closely together, so we can see colour and detail right in front of us. This is the area you use for reading.
• Further out, the light sensors aren't as close together, so you can't see as much detail. You also start to find rods. As you go further out, the rods become more common than the cones, until you can't see colour any more. This is why you couldn't identify the colour out as far as you could see the wriggling fingers.
• Out beyond where the cones end, you still have rods. They aren't very close together, so you can't really see any detail. But if something is moving, you may know something is there, even if you don't know what it is. This is the area you used to see the wiggling fingers.

A rough diagram showing how rods (grey) and cones (blue) are spread out around the retina.

I used to work in a road safety exhibition. One thing I learnt there is that younger people, especially people less than ten years old, tend to not have as much peripheral vision as older people. This is one reason why they need to be especially careful near the road and only cross at safe crossing points, like pedestrian crossings or traffic lights with pedestrian lights.