Week #5 Honorarium: Contrast Sensitivity

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An honorarium is often a small payment for services that might otherwise be done for free or for a much larger amount. Think of it as a token payment of appreciation.

Past experience with hybrid classes has shown that on the average 2 assignments a week is about right for most students. The problem is that there are many additional assignments that would enrich your learning in this class. I don't necessarily like the concept of extra credit (if you ask I'll be happy to tell you why) and I can't afford to pay you too much for doing these additional assignments because many students won't be able to find the time resources to do them and I don't want to blow out the grade curve.

So what I am willing to do is offer an honorarium as a token of my appreciation for doing these additional assignments. They will typically be worth 2 points. If you like you can incorporate this assignment into your Topical Blog Assignment by listing it as one of your references (in this case it is OK to 'double-dip').

For this week's honorarium assignment I would like you to go to the following site and read through the introduction and the instructions for the online lab experiment.

http://people.usd.edu/~schieber/coglab/CSFIntro.html

IMPORTANT: When you click on the button at the bottom of the page to "RUN THE EXPERIMENT" you may be asked to log in. If you log in as GUEST you should be able to get in. You will also need a computer with up to date Java plug-ins.

The experiment takes about 15 minutes - perceptually it seems like forever : -) but don't give up and don't just start clicking on buttons to get it over with because we want the data it provides you when you are done.

After all that, since most of the work was doing the assignment. For this blog post, just say I did the experiment and briefly discuss your experience.

Once you are done with your post make list of the terms and terminology you used in your post.

7 Comments

The website for this experiment was nice because you could control the contrast and see your personal boundaries. However, the experiment was partially flawed. When you can't see the difference between the two intervals, you have to guess, and when you guess you're given a 50/50 shot. I would assume this 50/50 shot would be too high to detect a scientifically significant "signal". If the experimental method provide different options to choose from, it may have been more accurate.

The interesting thing about the guessing is that this is the point where your subjective experience of the two contrasts is approximately equal. So, it is telling because it allows the researcher to know where your thresholds are at to detect the smallest difference between two contrasts.

I agree with wickert on the 50/50 shot assessment, this experiment was frustrating and sometimes I felt like I saw it and I wasn't actually sure. This was weird and it made my eyes hurt.

Psychophysics is tedious work. What did your data look like? Did they show you at the end?

I found myself guessing a lot too towards the end when the images were shown faster and the distinctions between the two images were less and less. This was very tedious, but it would be interesting to see where the average boundaries are.

You're getting to the fine details of the continuum where the values are very similar. Where you guess is the point where you can't resolve the difference in contrast between the two stimuli. Pretty interesting. How did your data look?

Towards the end of the experiment I too found myself guessing a lot. However, If I presented the stimuli over a few times, it was easier for me to detect it. It also helped me when I realized I needed to clean my computer screen. It was easiest for me to detect in the 4 and 64 and hardest for me at 16.

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