Filling in the gaps

As the kit might not have arrived, here's another bit of the vision project we should try an investigate... When we dissected the eyes, we saw where the optic nerve comes in - thats going to take up a bit of the retina kind of near the middle, but we don't see a hole in our view where the retina doesn't have space for photo-receptor cells. This is the 'blind spot', but it doesn't seem like we are blind there... We know that our brain does quite a lot of processing from the optical illusions we looked at at the start, and our brain helps here by filling in the missing part of the picture! How good is the brain?

Here is a simple test to measure where our blind spot is...

If you follow the link there are a series of additional test cards that show how good our brain is at making up missing data! We can make our own tests and see what our brain can fill in!

data

We need to record the data - that's what is real!
I hope everyone made notes, at the time, about what they saw with their eyes, as that is what was there!
Here is what your teachers gave you to describe a human eye...

Is that the same as you saw dissecting the pig's eye?

Here are a couple of the records of what we saw - there are more on our google+ photo site

 ...and... (!)

I eye

Ishihara

We are going to investigate colour vision so a first experiment is to give ourselves a colour blindness test. The standard test is the Ishihara Test with 38 cards. If we are lucky, we will have a colour blind person in the group and can compare their responses with other peoples!
Here is a link to an online test so you can test yourself (note that this is not a reliable diagnostic approach as screen display of colours can vary, but it should identify if you are completely colour blind!)

Can you see the coloured number?

Ha ha! That one is in black and white so as not to be unfair to colour blind people :)

We tried the real test and here are our results:

Hmm... what does it all mean? There are some indications that student 5 may have colour deficiency, and that possibly student 2 has discalculia (!) and that most of us weren't sure how to describe the test cards that had sxquiggly lines on... We can do some analysis on the spreadsheet but probably more interesting just to go back to those that had anomalous answers and check what they see!

A working hypothesis

The Feynman lectures on physics are an interesting read. It is for undergraduates really so it is quite a hard read in many places, but the chapter on colour vision is an interesting not-too-technical overview of how the eye works. 

You can read it online here!

I think this would constitute a good working hypothesis for some work to characterise and uantify our colour vision?

It's all in your mind...

To start things off, thinking about how good our sense of sight is as a scientific data collection instrument, we explored how accurate our powers of observation are and some ways in which we can get false observations (did you realise that was what you were doing?)

First we tested how selective our observations were. In this video...

...no one got the number of white player passes exactly right but everyone was close (a range of recorded passes of between 12 and 16 with the exact result being 15 so an error of up to 20% on just counting to 15!) and half the group did not record the additional interesting observation! It just shows how difficult it can be to make detailed observations particularly where the data do not fit our hypotheses – our mind filters the information and applies an interpretation to what we see before it gets into our conscious mind - let alone being able to keep it accurately in our memory.

Here are some some quite alarming illustrations of how selective our observations can be!

So if our brain is applying some data processing to the data sent from our eyes – how easy is it to exploit that processing to trick our brain into seeing more than is really there?

We started making 3d selfies – the pictures are just flat, but we can arrange for our eyes to each see slightly different things by using colour filters. The left eye gets a view that emphasises a photo taken from one position that is made redder by having a red filter in our ‘3D glasses’. The right eye has a blue (cyan actually which is green and blue) filter which cuts down the red light and dims the first photo whilst allowing green and blue light from a bluey photo taken from four inches to the right. It preferentially sees the right hand photo. Thus each eye is presented with a view mostly made up of the same image that it would get if it was looking at a real three dimensional person. Of course there is a bit of the photo still getting through to the wrong eye, and the colours are all a bit wrong, but our brain knows what it expects and can tidy up the signal that it is getting down the optic nerve: we ‘see’ normal colours and our brain decides that it is looking at a three dimensional person – neat! It is just a flat pattern of colours, but by giving the brain something that it is used to seeing, the brain tidies up any minor inconsistencies and sees what it wants to! Very cool for making arty pictures but a bit worrying for being accurate when doing experiments if what we ‘see’ is what we expect and our brain tries to get rid of anything unusual or interesting (like a gorilla perhaps!).

Here’s one of our 3D anaglyph selfies!

and another...

left

right

3D

And a link to the program that overlays the two photos.

Oh, and a dragon :)

Next week we will try and find more ways to use what we know the brain will do to make interesting pictures (optical illusions!) and also make auto-stereograms – a different way to trick the brain into thinking it is looking at a 3D object (and also to hide a message!)

Here are our photos

You've got to be good!

We are planning to do measurements on ourselves and to do some potentially dangerous things too. Before starting to do these sorts of experiments it is important to consider carefully the effect our research might have on:

1) Ourselves! (we want to survive this club!);

2) Other people – we must not hurt or upset anyone else;

3) Animals – they have (some) rights too;

4) The environment – we have to keep coming to school after the club ends so we’d better not mess it up! (and Mrs Gerrard would be upset if we made a mess of the school – see (2) above).

This is an ethics review. We have to do a review of these issues, every time, before we do any research at University or at the Corbet. We watched this video:

to remind ourselves that different people might be upset by things we thing are not a problem and we thought about everything that we might be doing. I think it’s all OK but before we go further we have written to parents so they are informed and can give consent on our behalf for everything we might do to each other (now Dr Herbert can start experimenting on everyone! - mwahh-ha-haa!).

Here is our ethic review.

Out of sight!

We have been given a grant by the Royal Society to do some science and to buy lots of cool equipment to help us do the science and (I hope!) have fun.

This picture works because close up our vision can interpret the high frequency features in the picture (the lines defining the wrinkles and messy hair and moustache of Einstein), but when we are further away we only see the low frequency (blurry) aspects (that define the curves and smooth hair shapes of Marilyn).