Kathy Maffei's blog

robot brain evolution

Projects: 
I submitted my final project html, but I don't see where they are going to be available for viewing. I hope a link is added so I read them all. Since a couple of people asked me to post the code from my project so they could fiddle with the robots, I posted my final project page (with links to the code) in my public folder. Hopefully, there's all the info you'd need to run it. Happy evolving!

Explanation for "saddle" pattern

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If you'll recall, we had a discussion yesterday in class about the "saddle" pattern seen in testing a range of input values (x & y each from 0 to 1) for the xor problem. There was some question as to why the saddle always ran like "/" rather than "\" Basically, the center range of x & y insisted on returning high values, even when Doug added training data for (0.5,0.5) to return 0. My intuition was that it had something to do with the calculations involved in adjusting the network's weights during back-propagation. Math isn't my forte (unfortunately, for a comp sci major!), but I'm pretty sure I've confirmed that the backprop algorithm is biased for answers of 1 over 0. Let me know if there's a hole in my logic, here.

GA Emergence Test Code

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As per Doug's request, here's my revision of Doug's emergence demo code. It's pretty simple. I added a second class, the same as his but with some adjustment in the fitness function to try to account for letters correct in a row. I marked the lines I added so I could later identify my changes. I also added three variables: trials (to indicate the number of trials to be run - and to make it easier to fiddle) and old & new to keep running totals of the number of generations each needed to achieve the correct phrase.

the emergence of the sensation of time

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The day I picked out my midterm book, I also came across another of interest that wasn’t on the list - The Quantum and the Lotus by Matthieu Ricard and Trinh Xuan Thuan - and I bought it to read later. My spouse beat me to it and has been pointing out passages from time to time. Last night he showed me one he thought related to our class, and he’s right. I transcribed it below to post for everyone because I thought it was fascinating:
    We probably feel the passing of time because of our cerebral activity. Data concerning the external world are transmitted by our sensory organs to our brain, which incorporates them into a mental picture. This cerebral activity brings into play simultaneously several separate regions of the brain with different functions. According to the neurobiologist Fransisco Varela, it’s the complexity of bringing together and integrating these various parts of the brain that gives us the sensation of time. This orchestrated, synchronous activity of large, discrete sets of neurons, among the hundreds of billions in the human brain, creates what scientists call an “emergent” biological state, that is to say a state, in this case the consciousness of time, that is more than the sum of its parts. Since this state lasts from a few tens to a few hundreds of a millisecond, we have the sensation of “now,” of a present with a duration. But this synchronization of neurons is unstable and doesn’t last. Its instability sets off other synchronous groupings of neurons, producing a succession of emergent states. They then give us the sensation of time passing. Each emergent state forks off from the preceding one, so that the previous one is still present in the succeeding one. This gives us the impression that time is continuous. (page 132)

Segregation Model

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Yes, yes, I agree with #1, and I understand that simple models may help define certain aspects, as opposed to the whole of a complex issue. I can see that and the utility of using them. But there are still a couple of observations about this model that I’d like to share: 1) My first interpretation of 50% preference was that it would imply no particular preference (which is why segregated results were so surprising when using 50% or less preference for difference), but this assumption isn’t true. After all, the test is still biased to a particular preference, no matter how low the %. It appears that the continuum of preferences would start at one end with 100% preference for similarity, progress on down to 0% preference for similarity, then to 0% preference for difference, on up through to 100% preference for difference at the other end of the scale. So, it seems to me that 0% of either would be truly no preference, and that there really is no surprise at seeing segregation resulting from a low similarity preference setting.

Growing a Tree

Projects: 
With Doug's help, I posted my tree growing model with some documentation that may be useful. There's a link on the page to download the nlogo file, in case it's of interest. Doug wanted me to document how to post netlogo aps. For BMC students: 1) make sure you have an html folder in your root directory called "public_html" and make sure it and your root directory both have read and execute permissions for everyone. You can also use a subdirectory within public_html - just be sure it has the appropriate permissions. 2) place a copy of your nlogo file in the public_html folder (or whatever subdirectory you want to use within public_html)and open it in Netlogo. You may want to edit the Information tab for your model because Netlogo will place this information in the html it creates when you ask it to save as an applet. Go to File -> Save As Applet... and save the html file it creates with the nlogo file in your public_html folder (or the subdirectory you're using). You can edit the html according to its directions.

more (or less) purpose

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Ok, I’m no philosophy major, but I’m going to try to better explain my feelings about the concept of purpose: To start, I find only 1 definition of the word purpose that appears to relate to our discussions: what something is used for. Sure, it’s also affected by context (i.e. “What’s your purpose for being in this building right now?” vs. “What is the program’s purpose?” vs. “the purpose of my existence”), but either way, it boils down to pretty much the same thing: function / use / reason. Now, I think it’s safe to say that anything and everything can have more than one use. Take for example something as straightforward as the Hello World program, which simply prints the statement “Hello, World” onto the screen. It can be said to have the purpose of printing “Hello, World” onto the screen, or its purpose could be to serve as a basic example for beginning programmers, or it might be used to quickly test your success at installing C libraries on your machine, etc.

Grand Unification Theory

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I just read through wikipedia's entry on emergence, and wanted to recommend it. There's a section explaining emergence in physics - phenomenon such as color and temperature are emergent properties of lower-level conditions that don't display those qualities but create them on a larger scale. Fascinating stuff. Anyway, it comes close to but doesn't actually say something I was thinking as I read through this section: that emergence might explain why Einstein's Grand Unification Theory has been so elusive. Emergence in physical laws would explain why quantum physics governs particles, why electromagnetic & weak forces govern atoms (composed of particles), and why mechanical laws govern larger bodies composed of those atoms.