Picturing science

Our energetic team submitted a number of entries to the Royal Society’s Picturing Science competition.

Jenny: This is an image I created in the scientific programming environment Matlab while doing some maths, trying to understand a particular aspect of stereo ("3D") vision. The funny thing is that I can now no longer even remember how I generated it! I think it is probably a Fourier phase spectrum of some sort. I threw up this image in my work, saved the figure, and carried on. Much later I came back to it and was struck by how beautiful and complex it is. In its repeating cells of interlocking curves, it reminds me of Celtic knotwork like that found in the Lindisfarne gospels.


Jenny: A occupational hazard of being a scientist's daughter is being roped into experiments. For this project, we were interested in where children looked when making judgments about pictures. We developed a system where we displayed pictures to children on a computer touchscreen; the children's eye-movements as they scanned the picture were monitored by an eye-tracker in front on them, and the children then touched the screen to indicate their judgment. We had the children sit on a carseat so that their head stayed in roughly the same position and the eyetracker didn't lose sight of their eyes. An adjustable arm helped us position the touchscreen at the right distance for each child, while the company Tracksys kindly loaned us an eyetracker. My little girl helped us get it all working and patiently recorded the words we needed for the experiment, so the computer could "speak" in a nice, friendly child's voice.


Jenny: This photo shows undergraduate student Steven Errington checking the calibration of a mirror stereoscope. This is one of the oldest forms of 3D display, and uses mirrors to present different images to the two eyes. The observer will sit with their head in the headrest in front of Steven, and the two mirrors in front of them will ensure that their left eye views a computer monitor to their left, while their right eye views a different monitor on their right. It's essential the two monitors are aligned both in space and time - that is, that they update their images at exactly the same time. Steven has clamped a photodiode in front of each monitor (that's the white cable running down by his hand) and fed their inputs into an oscilloscope. Photodiodes output a voltage which depends on the light falling onto them, so each new image presented on the computer monitor shows up as a "blip" on the oscilloscope. Steven can then check that the blips are occurring at exactly the same time, to sub-millisecond precision.


Jenny: Dr Ronny Rosner, an expert in insect visual neurophysiology, prepares to dissect a praying mantis in Dr Claire Rind’s insect lab at Newcastle University. This is part of a major new project in my lab, “Man, Mantis and Machine”, funded by the Leverhulme Trust. The praying mantis is the only non-vertebrate known to have a form of 3D vision, which it uses to help it strike at prey. We want to understand the neuronal circuits in its brain which help it do this, in order to compare them to similar circuits in human beings and other animals, and to 3D vision algorithms in computers and robots. Ronny will be joining my lab next year to bring his expertise to bear on these questions.

Paul: This experiment is designed to test orientation cues with stereo 3D (S3D) displays. The subject is sat behind a curtain with a square cut out of it, and can’t see that the television is in fact twisted through an angle, and therefore not perpendicular. However because of the display being S3D the subject cannot distinguish this change in orientation and assumes that the screen is frontoparallel (perpendicular). This means that when we show the stimulus (in this experiment a pair of rotating cubes) the stimulus look warped unless they are projected for the angle the subject is sat at (orthostereo), in contrast to when the curtain is removed and the television can be seen to be rotated, at which point the subjects brain corrects for not being perpendicular and sees the orthostereo cube (rendered for the angle) as warped, and the perpendicular cube as correctly projected.


Jenny: Three local sixth-formers did a summer project in my lab, funded by the Nuffield Foundation. As part of this, they collected experimental data from members of the public in Newcastle's Centre for Life. Here, they are getting their equipment set up ready for another busy data running experiments. Their work ended up being published in two scientific papers, on which the young people were authors, both in the journal i-Perception.



Zoltan’s diary: Monday 25/03/2013

Finally got the gadget to work. Tested against the results I managed to get earlier, and it seems to hold.

Since I am just about to finish this project (well, at least, time is up), it’s worth taking a look back: After fixing some experimental design issues, I got some wacky results. “Now that’s strange” I thought, and remained quite sceptical. It seemed so unrealistic, as the hypothesis was so straightforward that I was convincing that I will get the boring results everyone expected.

The results were nothing like it when I make the processing routines of course. What do you do in that case? You immediately assume that you have made a mistake at some point, and you have a list of suspected things you think might be held responsible. However, the results held against my every attempt to prove them inconsistent/wrong, and believe me, Jenny’s ‘vicious reviewer’ comments and my critical thinking made us to examine things thoroughly and systematically eliminate every factor that might have explained what we have seen or measured.

Today, I can say, that this three-week-long full-blown crusade against errors, mistakes and misinterpretations has failed. Going through thousands of measurements, quite a few display devices and even creating and using a purpose-built visual device (I couldn’t find an other name for it) have failed to do any harm to the credibility of the results.

end of line

Zoltan’s diary: Thursday 21/03/2013

After some fiddling with the code, the circuit works. Delays seem to be fine. Results seem to be fine. Found out how to control the serial port. I should upload some shell scripts to make life easier when using a campus pc. I managed to cover up the effect of the earth loops, so the circuit is stabilised properly.

Now, it’s on to matlab, and will need to spend time thinking about the implementation.

Zoltan’s diary: Wednesday 20/03/2013

Things now slow down a bit. I expected much more rapid progress with the micro. There were some obstacles that should not have been obstacles: The default reset value for an output pin is analogue input (took a good 3-4 hours to find out). My new USB/TTL UART doesn’t have the CTS/RTS pins wired internally to the power supply, so I can’t bypass flow control that easily (2-3 hours). The battery lasts around 5 hours in the oscilloscope (2×1 hour break). The poor thing sometimes re-sets because of interference. This will be solved as soon as I get rid of all the earth loops caused by the programmer, the UART and the oscilloscope and power supply.

Good news is that current-mode PWM powered LEDs are very closely linear. I managed to find my components in the morning (well, the components found me, actually…)

Zoltan’s diary: Friday 15/03/2013

The moral of today: One measurement is not a measurement. Practically the only two things I can do is to build the stimulator circuit and get an other photometer to make sure it’s not a calibration artifact. Then, all I can do is wash my hands how Pontius Pilate did. Then, I have locked out all possibility to have a misconducted measurement, and then, I can say is that my measurement is indeed correct no matter how wacky and unrealistic it seems. So the question is now if I have something publishable or more modest. Two weeks to go.

Zoltan’s diary: Thursday 14/03/2013

The weird result I am seeing is not caused by the monitor. Also, it is not caused by the different refresh rate and stabilised plate current. I am getting the same things over and over again, and the test show that there is a significant deviation to what I was expecting. I can’t think of any other thing I might have missed, and the results are pretty consistent. I currently have 10 matlab figures open and can see the same pattern over and over again. Okay, the coefficients are different, but the other monitor is brighter, smaller and behaves differently.

To do an other verification, I will make a circuit, and will check it with LEDs as well. This tendency should vanish.

Zoltan’s diary: Tuesday 12/03/2013

Do you know what is the answer to the ultimate question of life, the universe and everything? If you say 42, well, you are at least as much of a nerd as I am.

I think I found today the psychophysics equivalent of it: 1.4142136. I don’t want to jump into conclusions, so I am doing extra verification, replacing displays, redoing experiments, so I can be a hundred zillion percent sure that it’s not there because I forgot something. Guess I will find out in the next few days.

Also, I had my arm zapped for a good 20 minutes. Georgia was astonished how fast I found the nerve in my arm to test a reflex. Weird.

Zoltan’s diary: Monday 11/03/2013

Spent pretty much all day playing with Matlab. I have my experiment done (it works, verified), I also have my initial result processing script done (which also works, I verified it). What I don’t understand is why things go haywire when I sort the final array. As usual, I sort by the first column, but this time it seems that it doesn’t keep the rows. Anyway, I could get around it eventually, but it’s strange…

I also think I found an artifact in the results. Will need to replace the monitor to see if it’s real.

Zoltan’s diary: 08/03/2013

Got more results today. I see people getting bored with the experiment. For instance, my arm will be zapped for two hours in exchange for an experiment. But also it includes the more generous spreading of chocolate, teas, etc.

I have a theory on how we should mathematise the findings, we’ll see if it stands…