Month: December 2007

Adventures in Eating and Sleeping

Seth Roberts4 Comments

Since the beginning of time everyone has been eating and sleeping — a lot. If you thought this meant there couldn’t be any new and cool twists on these activities, you’d be wrong.

1. Eating. “Last night I tried to “race myself” because I knew I would get full fairly quickly but I really enjoyed what I was eating so I ate fast.” This is from the SLD forums. Outcome of race: Lost. “I still couldn’t get through the whole salad, just too full to eat another bite. That’s amazing to me.”

2. Sleeping. Someone I know used to wake himself up in the middle of the night because he enjoyed falling asleep.

Experimental Mathematics

Seth RobertsLeave a comment

The journal Experimental Mathematics, started in 1992, publishes “formal results inspired by experimentation, conjectures suggested by experiments, descriptions of algorithms and software for mathematical exploration, [and] surveys of areas of mathematics from the experimental point of view.” The founder wanted to make clearer and give more credit to an important way that mathematicians come up with new ideas. As the journal’s statement of philosophy puts it, “Experiment has always been, and increasingly is, an important method of mathematical discovery. (Gauss declared that his way of arriving at mathematical truths was “through systematic experimentation.”) Yet this tends to be concealed by the tradition of presenting only elegant, well-rounded, and rigorous results.”

When John Tukey wrote Exploratory Data Analysis (1977), he was doing something similar: shedding light on how to come up with new scientific ideas plausible enough to be worth testing. Tukey obviously believed this was a neglected area of statistics research. I was told that the publisher of EDA was uninterested in it; they only published it because it was part of a two-book deal. The other book, with Frederick Mosteller, was more conventional.

My paper titled “ Self-experimentation as a source of new ideas” made the same point as Tukey about an earlier step in the scientific process: data collection. How to collect data to generate new ideas worth testing was a neglected area of scientific method. Self-experimentation, derided as a way of testing ideas, might be an excellent way of generating ideas worth testing.

I think of it as crawling back into the water. In the beginning, all math was conjecture and experimentation. In the beginning, all data analysis was exploratory. In the beginning, all science was tiny and devoted to coming up with new ideas. From these came methods of proof, confirmatory data analysis, and methods of carefully testing ideas. Human nature being what it is, users and teachers of the new methods came to greatly disparage the earlier methods. Gary Taubes told me that he spoke to several obesity researchers who thought that the field essentially began with the discovery of leptin. Nothing before that mattered, they believed.

Thanks to Dev Rana.

Eskimos, Heart Disease, and Omega-3s: The Plot Thickens

Seth Roberts3 Comments

David Marcus made the following comment on an earlier post:

It’s a myth that Eskimos have low rates of heart disease. Actually, recent studies have shown they have high rates of cardiovascular disease (50% higher than western populations) despite diets that are very high in fatty fish.

Mr. Marcus makes a very good point (and it is wonderful to get such informative feedback). Myth is wrong. A Greenland doctor’s casual observation — Eskimos almost never died of heart attacks — was confirmed by a detailed study, published in Acta Medica Scandinavica in 1980. A r ecent study, however, found this:

OBJECTIVES: The thirty-year-old hypothesis that omega-3 fatty acid (FA) may “reduce the development of thrombosis and atherosclerosis in the Western World” still needs to be tested. Dyerberg-Bang based their supposition on casual observations that coronary atherosclerosis in Greenlandic Inuit was ‘almost unknown’ and that they consumed large amounts of omega-3 FAs. However, no association was demonstrated with data. STUDY DESIGN: Cross-sectional study. METHODS: 454 Alaskan Eskimos were screened for coronary heart disease (CHD), using a protocol that included ECG, medical history, Rose questionnaire, blood chemistries, including plasma FA concentrations, and a 24-hour recall and a food frequency questionnaire assessment of omega-3 FA consumption. RESULTS: CHD was found in 6% of the cohort under 55 years of age and in 26% of those > or = 55 years of age. Eskimos with CHD consume as much omega-3 FAs as those without CHD, and the plasma concentrations confirm that dietary assessment. CONCLUSIONS: Average daily consumption of omega-3 FAs among Eskimos was high, with about 3-4 g/d reported, compared with 1-2 g/d used in intervention studies and the average consumption of 0.2 g/d by the American population. There was no association between current omega-3 FA consumption/blood concentrations and the presence of CHD.

A well-written abstract, by the way.

Science is like a game of telephone. It would be truly weird if the initial observation was wrong, given that it was later confirmed in detail and productively followed up — and no one doubts that omega-3 increases clotting time. But “replications” are never exact. This study, for example, measured “in vivo” CHD, whereas the initial observation was about causes of death. The group of Eskimos studied is probably different; and their lifestyle, especially their diet, may have changed substantially in the last 30 years. On the other hand, these new observations are consistent with the great difficulty there has been in confirming the idea that omega-3 fats reduce heart disease.