Spotlight, November 26, 2014: Kurtosis
Image credit: whatilearned.wikia.com
Kurtosis is a description of how sharply peaked a statistical distribution is and how far from the horizontal axis (how heavy) the tails are. The normal distribution has a kurtosis of 3 and moderately heavy tails and is called mesokurtic. Distributions that are pointier with heavier tails (farther above the horizontal axis) than the normal distribution are called leptokurtic, and those flatter than normal and with lighter tails are called platykurtic. Because of this relationship between the peakedness and the weight of the tails, leptokurtic distributions also have sides with greater curvature than the sides of mesokurtic and platykurtic distributions.
Sources: Weisstein, Eric W. “Kurtosis.” From MathWorld–A Wolfram Web Resource. http://mathworld.wolfram.com/Kurtosis.html (if you like math). Decarlo, Lawrence T. “On the Meaning and Use of Kurtosis.” Psychological Methods 2.3 (1997): 292-307. (if you like math drama)
“Big man” Drizzt
I sometimes call my sister “bo,” but other than that I refer to the humans in my life by their given names or common substitutions like “mom” or “dad”. On the other hand, I almost never refer to my pets by the names I decided they should have unless I’m talking about them to someone else. Yes, that does mean that I often talk to my pets directly. I call Drizzt, my bearded dragon, “big man” or “Drizzt-y-pie.” My American cat Isabelle is “pitoo” or “boo-boo,” while my Swiss cat Zora is “snuggle pumpkin,” “buckets,” or “butthead” (when she’s being annoying).
I have called every pet I’ve ever had by some cutsey name or, more often, a totally random word or sound. In the reverse, no one I know has a pet name for me as far as I am aware. One time, a friend suggested “kakes,” but it didn’t stick. Why do people use pet names at all? Is there some kind of mental or social benefit to that kind of communication? More importantly for me, why do I use pet names for animals but not for people? What does that say about me?
Photo credit: http://www.vaccines.gov
Imagine that you’re at the mall and you see someone you don’t like – maybe an ex or that annoying kid from high school – but the mall is crowded that day and you can easily blend into the crowd and escape. Now imagine that the mall isn’t crowded. This unsavory person sees you and walks over. Because there aren’t a lot of people around for you to hide among, now you have to talk to someone you’d really rather avoid. In the case of infectious diseases, what actually happens is your body becomes the feeding ground of an organism whose numbers have been so long controlled by preventative medicine that they have all but faded from cultural memory.
Spotlight, November 17, 2014: Swan swim speed
Mute swan on the Limmat River near Zurich Hauptbahnhof.
Every day I commute into the city of Zurich, and I walk past swans and ducks cavorting or sleeping on the Limmat River by the train station. I noticed one evening that the swans can swim surprisingly fast. It turns out that swans are the fastest swimmers and fliers of any waterfowl, as well as one of the longest lived of all birds. I discovered that they can fly at speeds of up to 50 mph, but I was unable to find any information about their swimming speed. In fact, my Google search turned up several entries from Dwarf Fortress Wiki and one hit through answer.com (how fast do swans swim?). The answer provided for that question was “swans swimm so fast at lest 100 mile pore awer,” so it didn’t seem to me like the most credible source.
I decided to calculate my own answer. I measured my shoe (25 cm) and used my steps to pace off the length of a room (26 steps). Then I timed myself walking through the room at the pace I best remembered for the swan on the Limmat (13 seconds). That comes out to a standard traveling-perpendicular-to-the-current speed of 0.5 m/s or ~1.12 mph. Not bad. That’s faster than I can bike uphill.
Photo credit: news.nationalgeographic.com
I’m reading a book right now (Plagues and Peoples by William H. McNeill) that at one point compares the spread of early humans out of Africa to a disease. He has a good argument, saying that the ability of humans to use technology allowed them to mutate, in effect, faster than local wildlife could respond and comparing human expansion to a pandemic. I might have used an invasive species as a metaphor rather than a disease because in this case it wouldn’t really be a metaphor – humans were at the time an invasive species. But in a book about pathogenesis in humans, such a comparison is apt.
So here is the question: to what extent is our history as a species inevitable?
Photo credit: https://www.facebook.com/mfeminism/
When I first read this post about Wonder Woman by A Mighty Girl (http://www.amightygirl.com/), there was a comment by a woman who said that she didn’t mind the qualification “for a girl” because men are biologically stronger than women.
I do not accept this reason.
1. There is a difference between saying a characteristic is due to biology versus saying that it’s due to genetics. Men are not biologically stronger. The only biological difference between men and women is in the gonads and reproductive organs: men have testes (etc.) and women have ovaries (etc.). Continue reading
Spotlight, November 7, 2014: Ẽṭo
Food customs in North India are influenced by the idea of ẽṭo (pronounced, as closely as I can determine: engtao). Ẽṭo can refer either to food which has come into contact with the eater’s saliva and therefore become permeated with his or her essence or to the state of being so permeated due to contact with the mouth or another object which is ẽṭo. Your hands can easily become ẽṭo if you hold a cup while drinking or a fork while eating, so you must wash your hands immediately afterward in order to prevent the spread of this ẽṭo condition.
By touching an object or food that another person has made ẽṭo, you take in some of their essence, so people are very careful around those from whom they wish to stay distant. On the other hand, people who wish to be close to someone else (e.g. a wife to a husband, a servent to an employer, or close friends or siblings among themselves) will often freely share food. Such fastidiousness likely prevents the spread of disease, and the custom provides a form of social structure.
Source: Lamb, Sarah. White Saris and Sweet Mangoes: Aging, Gender, and Body in North India. Berkeley: U of California, 2000. 30-34. Print.
I first saw this image on a calendar that one of my college professors had. It’s meant to be tongue-in-cheek, but I’ve met people who hold this opinion steadfastly and without humor. Photo credit: www.despair.com
Why do we think taxes are bad? Why do we characterize them as unfair, as an immense and crushing burden? Why do we let politicians use taxation rhetoric to influence us?
I have always been confused by the way Americans think about taxes. By living in this country as citizens, we all agree to contribute money to build roads that facilitate trade, to provide medical care to the poor so that we can curtail the spread of disease, to educate our children so that they can participate effectively in an advanced civilization, and to defend ourselves from invaders. Continue reading