Human Spark

April 17, 2010

What up, Señor Trapper John, M. D.?  Thanks for setting the table for me to mention this brief note I wrote after Paths Ahead, which includes some discussion about storytelling and what a solution is.  In less than a week into my foray into the industrial world, I picked up some new jargon related to this discussion of ours: the DIKW pyramid, where the four levels are data, information, knowledge, and wisdom.

Did you see any of the three-part miniseries on PBS hosted by Alan Alda on what makes humans different from other animals, especially other primates, and especially in the area of intelligence?  If you didn’t, you can watch the full episodes online.  I thought it was really interesting.  For a preview of the type of stuff in the miniseries, take a look at this column.  The Discovery Channel series Life features primates this week, which might be interesting as well.

I wouldn’t call myself an expert in dimensionality reduction and supervised classification, but I wouldn’t call myself a birdbrain in the subject either.  Coming to your Bumpus sparrow data challenge and whether brain size predicts survival, let me first describe the dataset a bit.  There are eleven measurement dimensions: sex, age (adult or young, provided only for males), total length, alar extent (wingspan), weight, length of beak and head, length of humerus, length of femur, length of tibiotarsus, width of skull, and length of keel of sternum.  Some sparrows perished and some survived a severe storm.  Presumably the two features: length of beak and head, and width of skull are related to brain size.

The logistic regression done by Janzen and Stern that you linked to was done on males and females separately and did not consider age.  (I suspect this is because categorical variables and missing data are not well handled by logistic regression.)  The technique outputs a weight vector equal in length to the number of features, whose magnitude may be interpreted in certain situations to show the relative importance of the different features.  For the males, the top two features were total length and weight.  Skull width was sixth, and the length of head and beak came in eighth out of nine.

I did a similar analysis using the random forest classifier, which readily handles categorical data and missing values and provides a measure of feature importance based on the classification error on permuted “out-of-bag” data.  Here are the feature importance values I found.


Here again, total length is first, and weight is second.  The length of beak and head is seventh and width of skull is last out of eleven.  This analysis and the logistic regression analysis seem to indicate that the head size features are not predictive of survival.

However, what is obscured in the analysis is the relative body part lengths and widths because of the overall scaling of the birds.  I redid the same random forest feature importance calculations but this time, I divided the alar extent, width of skull, and the five smaller lengths by the total length for each bird, and used those normalized measurements as the features.  The importance values are quite different.

The total length and weight don’t dominate.  The two head size features are right there after alar extent and length of humerus.  Long wings are unsurprisingly really important, but after that, head size is important as well.  I wouldn’t go so far as to say that this shows that large brain size leads to survival, but that possibility isn’t precluded by this simple analysis either.  There is a story to be told, but I don’t see the story being a scientific law.



  1. […] I return to the inner frame of allied informational topics?  In your Human Spark post, you took the Bumpus sparrow data and tried to create knowledge from it.  In particular, you […]

  2. […] was an interesting read for me.  It touches on various things that I have interests in, including storytelling (which I learned a bit about from Prof. Minkowski), semantics and pragmatics (which I learned a bit […]

  3. […] Jorge Luis Borges, light has always been, and I think will always be, a metaphor for wisdom (or knowledge or information or data).  From that perspective, the observation that everyone (current and historical) spends about the […]

  4. […] David Ferrucci’s), and is related to storytelling thoughts I have shared here previously (1, 2, […]

  5. […] in allometric scaling laws for various things, and I suppose I’ve made you at least somewhat interested.  When I was visiting Santa Fe last summer, I feel like my interest in this topic was renewed, […]

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  7. Thanks for finally talking about >Human Spark | Information Ashvins <Loved it!

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