(3089/898) Gould: Full House

2248) [P]robably more intellectual energy has been invested in discovering (and exploiting) trends in the stock market than in any other subject - for the obvious reason that the stakes are so high, as measured in the currency of our culture. The fact that no one has ever come close to finding a consistent way to beat they system - despite intense efforts by some of the smartest people in the world - probably indicates that such causal trends do not exist, and that the sequences are effectively random.

Stephen Jay Gould
Full House (1996)

2249) In the second most prominent fallacy about trends, people correctly identify a genuine directionality, but then fall into the error of assuming that something else moving in the same direction at the same time must be acting as the cause. This error, the conflation of correlation with causality, arises for the obvious reason (once you think about it) that, at any moment, oodles of things must be moving in the same direction (Halley's comet is receding from earth and my cat is getting more ornery) - and the vast majority of these correlated sequences cannot be causally related. In the classic illustration, a famous statistician once showed a precise correlation between arrests for public drunkenness and the number of Baptist preachers in nineteenth-century America. The correlation is real and intense, but we may assume that the two increases are causally unrelated, and that both arise as consequences of a single different factor: a marked general increase in the American population.

Stephen Jay Gould
Full House (1996)

2250) The chess board is the world, the pieces are the phenomenon of the universe, the rules of the game are what we call the laws of Nature. The player on the other side is hidden from us. We know that his play is always fair, just, and patient. But also we know, to our cost, that he never overlooks a mistake, or makes the smallest allowance for ignorance.

T.H. Huxley
A Liberal Education (1868)
quoted by Stephen Jay Gould in
Full House (1996)

2251) Huxley's metaphor fails [...] because we cannot depict the enterprise of science as Us against Them. The adversary at the other side of the board is some complex combination of nature's genuine intractability and our hidebound social and mental habits. We are, in large part, playing against ourselves. Nature is objective, and nature is knowable, but we can only view her through a glass darkly - and many clouds upon our vision are of our own making: social and cultural biases, psychological preferences, and mental limitations (in universal modes of thought, not just individual stupidity.)

Stephen Jay Gould
Full House (1996)

2252) We often portray taxonomy as the dullest of all fields, as expressed in a variety of deprecatory metaphors: hanging garments on nature's coatrack; placing items into pigeonholes; or (in an image properly resented by philatelists) sticking stamps into the album of reality. All these images clip the wings of taxonomy and reduce the science of classification to the dullest task of keeping things neat and tidy. But these portrayals [...] reflect a common fallacy: the assumption of a fully objective nature "out there" and visible in the same way to any unprejudiced observer [...] If such a vision could be sustained, I suppose taxonomy would become the most boring of sciences. for nature would then present a set of obvious pigeonholes, and taxonomists would search for occupants and shove them in - an enterprise requiring diligence, perhaps, but not much creativity or imagination.

But classification systems are not passive devices in a world objectively divided into obvious categories. Taxonomies are human decisions imposed upon nature - theories about the causes of nature's order. The chronicle of historical changes in classification provides our finest insight into conceptual revolutions in human thought. Objective nature does exist, but we can converse with her only through the structure of our taxonomic systems.

We may grant this general point, but still hold that certain fundamental categories present so little ambiguity that basic divisions must be invariant across time and culture. Not so - not for these, or any subjects. Categories are human impositions upon nature (though nature's factuality offers hints and suggestions in return).

Stephen Jay Gould
Full House (1996)

2253) [T]he three standard measures of central tendency, or "average" value - the mean (or conventional average calculated by adding all the values and dividing by the number of cases), the median (or halfway point), and the mode (or most common value). In symmetrical distributions, all three measures coincide - for the center is, simultaneously, the most common value, the halfway point (with equal number of cases on either side), and the mean. This coincidence, I suspect, has lead most of us to ignore the vital differences among these measures, for we view "normal curves" as, well, normal - and regard skewed distributions (of we grasp the principle at all) as peculiar and probably rare. But measures of central tendency differ in skewed distributions - and a major source of employment for economic and political "spin doctors" lies in knowing which measure to choose as the best propaganda for the honchos who hired your gun. [...]

In general, when a distribution is prominently skewed, mean values will be pulled most strongly in the direction of skew, medians less, and modes not at all. Thus, in right-skewed distributions, means generally have higher values than medians, and medians higher than modes. If we start with a symmetrical distribution (with equal mean, median, and mode), and then pull the variation to form a right-skewed distribution the mean will change most in the direction of skew - for one new millionaire on the right tail can balance hundreds of indigent people on the left tail. The median changes less, for a single pauper will now compensate the millionaire when we are only counting noses on either side of a central tendency. (The median might not move at all if only the wealth, and not the number, of people increases on the right side of the distribution. But if the number of wealthy people at the right tail increases as well, then the median will also shift to the right - but not so far as the mean.) The mode, meanwhile, may well stay put and not vary at all, as mean and median grow in an increasingly right-skewed distribution. Twenty-thousand per year may remain the most common income, even while the number of wealthy people constantly increases.

Stephen Jay Gould
Full House (1996)

2254) What are the real success stories of mammalian evolution? We can answer this question without ambiguity, at least in terms of numerous species and vigorous radiation: rats, bats, and antelopes [...] These three groups dominate the world of mammals, both in numbers, and in ecological spread.

Stephen Jay Gould
Full House (1996)

2255) The obvious main difference between Darwinian evolution and cultural change clearly lies in the enormous capacity that culture holds - and nature lacks - for explosive rapidity and cumulative directionality. In an unmeasurable blink of a geological eyelash, human cultural change has transformed the surface of our planet as no event of natural evolution could ever accomplish at Darwinian scales of myriad generations. (Natural catastrophes of a physical nature, like the bolide that triggered the great Cretaceous extinction, may wipe out many forms of life in a geological moment, but no known process can produce natural evolutionary change at anything like the speed and extent of human cultural transformation; the impressive and maximal rapidity of the Cambrian explosion lasted some 5 million years.

Stephen Jay Gould
Full House (1996)

2256) Cultural change [...] receives a powerful boost from amalgamation and anastomosis of different traditions. A clever traveler may take one look at a foreign wheel, import the invention back home, and change his local culture fundamentally and forever. One brace of guns, one bevy of war chariots, imported with engineers and tradesmen to keep them in working order, can transform a limited and peaceful state into an expanding engine of conquest. The explosively fruitful (or destructive) impact of shared traditions powers human cultural change by a mechanism unknown in the slower world of Darwinian evolution.

Stephen Jay Gould
Full House (1996)

2257) [T]he great fuzziness of our age - so-called "political correctness" [...] a doctrine that celebrates all indigenous practice, and therefore permits no distinctions, judgments, or analyses.

Stephen Jay Gould
Full House (1996)