probability and public policy VII: cancer

[part one of this series here]

The variety of interpretations of probability is supplemented by a variety of applications. Unfortunately, the most certain and convenient applications of statistical analysis (those implementable in scientific experiments) don't often provide an answer to our questions about how to act in an uncertain world.

Causal connections, for example, are notoriously difficult to justify: how can we separate the case where smoking causes cancer from that where smoking and cancer share a mutual cause (say, a gene predisposing one to both the practice of smoking and the tendency to contract cancer)? The problem is a vexed one, but it misconstrues the situation. Such questions about causality can always be reduced to the more pertinent: how should I act?

This latter question, the question of what to do, is precisely one the answer to which can never be "read off" statistical analyses. Although there are some cases where the answer may be clear (if analysis determines the probability that you will die if you leap off a 15 storey building to be 98%, you probably shouldn't jump off that building), in most cases, the answer provided by a statistical analysis will be orthogonal to the question of what to do. Some examples:

Threshold Effects

Consider, for example, the question: Does the sugar substitute saccharin cause cancer? In fact, this question is largely irrelevant to the more pertinent: Should I ingest saccharin?

Suppose a study demonstrates that feeding lab mice some substantial amount of saccharin each day dramatically increases the probability that they will contract cancer. This seems to demonstrate, fairly conclusively, that, in some sense, saccharin "causes" cancer.

However, many of the natural substances ingested regularly by human beings would cause serious medical problems if consumed in suitably large amounts. The problem here is that there is a threshold for such substances: less than some amount, and they are easily processed by the body; once that amount is surpassed, however, there is a sudden increase in the probability that the body will suffer ill effects.

So, the result that saccharin "causes" cancer in some sense is irrelevant to the determination of "safe" behavior; really, we must know what the pertinent threshold for saccharin is: how much must be ingested before the chance of getting cancer spikes? How close is this threshold to the amount of saccharin I might consume on a daily basis? In the words of E. T. Jaynes, Probability Theory, 2003:

For virtually every organic substance (such as saccharin or cyclomates), the existence of a finite metabolic rate means that there must exist a finite threshold dose rate, below which the substance is decomposed, eliminated, or chemically altered so rapidly that it causes no ill effects. If this were not true, the human race could never have survived to the present time, in view of all the things we have been eating.

Indeed, every mouthful of food you and I have ever taken contained many billions of kinds of complex molecules whose structure and physiological effects have never been determined - and many millions of which would be toxic or fatal in large doses. We cannot doubt that we are daily ingesting thousands of substances that are far more dangerous than saccharin - but in amounts that are safe, because they are far below the various thresholds of toxicity. At present there are hardly any substances, except some common drugs, for which we actually know the threshold.

Therefore, the goal of inference in this field should be to estimate not only the slope of the response curve but, far more importantly, to decide whether there is evidence for a threshold; and, if there is, to estimate its magnitude (the 'maximum safe dose'). For example, to tell us that a sugar substitute can produce a barely detectable incidence of cancer in doses 1000 times greater than would ever be enountered in practice, is hardly an argument against using the substitute; indeed, the fact that it is necessary to go to kilodoses in order to detect any ill effects at all, is rather conclusive evidence, not of the danger, but of the safety, of a tested substance. A similar overdose of sugar would be far more dangerous, leading not to barely detectable harmful effects, but to sure, immediate death by diabetic coma; yet nobody has proposed to ban the use of sugar in food.

Modeling Continuity where Discreteness is Needed

A related problem to that of threshold is how to take a continuous model and parse it into the discrete chunks relevant for discussion in natural language and, by extension, policy decision.

Consider, for example, the question of whether or not second hand smoking laws are scientifically justified. Research that shows second hand smoke is "just as dangerous" as "first hand" smoke depends upon data involving the ingestion of equivalent amounts of smoke. Second hand smoke disperses, however, and is not inhaled by bystanders with the same intensity as "first hand" smoke. The pertinent question, then, is not is second hand smoke dangerous?, but rather, at what distance, and in what ventilation conditions is second hand smoke dangerous?

The dispersal of second hand smoke is a phenomenon suitable for statistical modeling. Such models do not tell us what is safe, however, merely the density of particles due to second hand smoke at various distances from the source in various ventilation conditions. Here, we have a continuous phenomenon, the dispersal of second hand smoke, and a discrete classification, safe or not safe. The problem is that statistical modeling of the continuous situation does not fully determine the locus upon that continuum of the boundary between safe and non-safe; yet it is this second question which is relevant to policy decision.

For example, a recent Stanford University study, one of the first peer-reviewed articles on the topic, emphasizes the support of their findings for public conceptions about second hand smoke dispersal (the results are summarized here), in particular, as evidence for a ban on smoking in public places. However, personal communication with one of the graduate students working on the project revealed that at prior stages of analysis there was surprise at how little public fears were confirmed and how little justification for such laws could be found. Whence this apparent disagreement? The study shows that, on the one hand, yes, there are quite high levels of particles in the air near an outdoor smoker; on the other hand, the density of particles drops off quite dramatically within a fairly small distance of the smoker and is highly susceptible to ventilation effects. Furthermore, the effect lasts for a relatively short time. Since the "safe" background level of particles is defined in terms of average density over a 24 hour period, it is not all clear how the localized and relatively short period of increased particle density compares with that contributed by, say, a passing car.

The Clustering Illusion

The clustering illusion occurs when humans see patterns in "random," or mathematically unpatterned, data. Everyday examples of this phenomenon include hearing the murmur of voices in the sound of a bubbling brook, the perception of a gambler that he is on a "winning streak," and instances of religious pareidolia, such as the "nun bun."

Such perceptions of non-existent pattern are relatively benign, however, as the poor choices they inspire tend to effect only a handful of individuals. When the objects of the illusion are potentially relevant to public policy, however, the clustering illusion can waste millions of dollars, inspire fear, and generate spurious "research." An example is the power lines ~ leukemia scare.

Law suits, local legislation, and widespread fear were caused throughout the '80s by the idea that power lines might, via their surrounding electromagnetic fields, somehow increase the possibility that a child contracts leukemia (or, perhaps, some other form of cancer). The inspiration for the studies centered on clustering phenomena, in particular, the apparent clustering of leukemia sufferers in a neighborhood "near" power lines. Subsequent research demonstrated conclusively that there was no measurable correlation between proximity to power line generated magnetic fields and tendency to contract leukemia, a result consonant with current scientific theories of magnetic fields. Nevertheless, public misconception and superstition persist; the damage of misguided and statistically unfounded claims continues to play out in the those corners of the public sphere dominated by paranoia and underinformed superstition.

A nice summary of the issue by Edward Campion can be found here. We quote only the conclusion:

Serious limitations have been pointed out in nearly all the studies of power lines and cancer. These limitations include unblinded assessment of exposure, difficulty in making direct measurements of the constantly varying electromagnetic fields, inconsistencies between the measured levels and the estimates of exposure based on wiring configurations, recall bias with respect to exposure, post hoc definitions of exposure categories, and huge numbers of comparisons with selective emphasis on those that were positive. Both study participation and residential wire-code categories may be confounded by socioeconomic factors. Often the number of cases of [acute lymphoblastic leukemia] in the high-exposure categories has been very small, and controls may not have been truly comparable. Moreover, all these epidemiologic studies have been conducted in pursuit of a cause of cancer for which there is no plausible biologic basis. There is no convincing evidence that exposure to electromagnetic fields causes cancer in animals, and electromagnetic fields have no reproducible biologic effects at all, except at strengths that are far beyond those ever found in people's homes.

The point here is not just that fear and irrational paranoia on the part of the public can motivate policy choices (in contradiction to or via abuse of the results of statistical analysis), but further that such paranoia can motivate bad research and lower standards of scientifc rigor from those necessary to ensure meaningful results.

next: intelligent design

parable R

In the Kingdom of Decadence, where indulgence reigns and self-aggrandizement the weathercock of virtue guides, the lepers of sense their jealous rage did leash 'pon unsuspecting proletarian dreams, draining and desaturating symbolism from symbol, meaning from meant.
Babel forthwith her tremulous head did raise, aquiver in apprehension, expectation primed by cryptographic sensuality; a bevy of humpty-dumptyisms, anomalous intensions, swarm the façon de parler of the plebs, scum-drenched street urchin babbling in tongues like holy men, and with the mutant language, visions, themselves mutations of normal thought, a perversion upon the mind's eye.
And inward turned, the gaze of the "I" lit upon the mishapen folds of the language organ, piercing, incising, invigorating its dormant telos, embarrassing its ego, with efficient and sensitive touch, releasing, relinquishing, remanding, and constructing anew syllable, that subtle tempo, the pacemaker of thought: word.

understanding the mind IX

Coming as I do between psyche anatomized and psyche synthesized, I must define my terms that I can bridge the traditional gulf between mind and body and the technical gap between things begotten and things made.

By the term "mind," I mean ideas and purposes. By the term "body," I mean stuff and process. Stuff and process are familiar to every physicist as mass and energy in space and time, but ideas and purposes he keeps only in the realm of discourse and will not postulate them of the phenomena he observes. In this I agree with him, but what he observes is some sort of order or invariance in the flux of events. Every object he detects in the world is some sort of regularity. . .

To detect regularities in the relations of objects and so construct theoretical physics requires the dsciplines of logic and mathematics. In these fundamentally tautological endeavors we invent surprising regularities, complicated transformations which conserve whatever truth may lie in the propositions they transform. . . . It is these regularities, or invariants, which I call ideas, whether they are theorems of great abstraction or qualities simply sensed.

But let us now compel our physicist to account for himself as a part of the physcial world. In all fairness, he must stick to his own rules and show in terms of mass, energy, space, and time how it comes about that he creates theoretical phsyics. He must then become a neurophysiologist. . . , but in so doing he will be compelled to answer whether theoretical physics is something which he can discuss in terms of neurophysiology. . . To answer "no" is to remain a physicist undefiled. To answer "yes" is to become a metaphysician—or so I am told.

Warren S. McCulloch, "Why the Mind is in the Head," 1951

authorial intent: there will be blood

A puzzling, but compelling film.

One particularly interesting aspect are the brothers Paul and Eli Sunday, both played by Paul Dano. Although the wikipedia entry has since been altered (?), mere days ago it contained a section (4.1, if memory serves) on the Paul / Eli Sunday debate (see, for example, here), one of the most interesting sections of the entry, bizarrely removed by busybody Jim Dunning. The issue is this: are they twin brothers, or a single (schizophrenic?) person?

In favor of the former interpretation is Paul Thomas Anderson's intent - according to the now missing section of the wikipedia article, the decision to cast Eli Sunday with Paul Dano was made after filming had already commenced, and Dano's part as Paul Sunday had already been filmed. Purportedly, a younger actor playing Eli was replaced mid-filming (possibly due to Daniel Day Lewis' intimidating practice of staying perpetually in character). The brothers interpretation is also supported by the script.

However, the two characters never appear in the same scene, and Eli exhibits schizophrenic behavior in other scenes (he is, after all, a revivalist preacher who "casts the devil" out of his sick parishioners). When Daniel Plainview (Lewis) taunts Eli by telling him how much he paid Paul Sunday for information about their farm, giving a falsified amount, he almost seems to be daring Eli / Paul to admit his deceit, to break free from his schizophrenia. (Also, note that Paul questions Lewis on his religion before Eli even comes into the picture.)

The question, though, is not what interpretation we want to give here, but rather, what interpretation are we permitted to give - may we consider the author "dead" even as he walks among us, decrying our attempts at interpretation? Of course, most of you reading this will give the quick and obvious answer - but will you all give the same one?

bowling

information terrorism

Knowledge has always meant power, but knowledge must be combined with raw materials to realize that power. Knowledge of how to build a catapult is useless without the resources to both build a catapult and transport it to your enemy's doorstep.

Throughout history, tyranny has prevailed over enlightenment due to its possession of sufficient resources, not just to realize the fruits of knowledge, but, perhaps more importantly, to control the flow of knowledge.

Such a system is self-perpetuating and induces the illusion that it is the only viable, or only rational, solution to the problem of coordinating activity amongst a heterogenous population.

In the age of the internet and the linked in computer, however, both the resources needed to realize knowledge, and those needed to transport it to one's enemy's door have diminished exponentially. For the ubiquity of the computer for the purposes of organizing information has ensured that everyone is vulnerable to attack. The catapult can be realized with a few lines of code, and the internet offers a highway to transport it to your door.

Although the individual is put at risk, so much more so those authoritarian organizations which had heretofor supressed knowledge through their control of resources, both labor and materials, and, perhaps more importantly, their control of the flow of knowledge. In the modern age, all information is virus, permeating the internet, infecting those who are linked in.

Not only political bodies have abused this power, yet now find themselves threatened. Consider, for example, ANONYMOUS' threat against Scientology:



ANONYMOUS is (supposedly) a cabal of secret "superhackers" (though they themselves claim to include divers members of society, from lawyers to "veterinary technicians"). They threaten Scientology with vigilante justice of some kind. So far, success of related groups has been limited; however, the response by Scientology is just the typical move of the authoritarian ~ throw more resources (money) at the problem, in this case, primarily for purchasing the knowledge of others.

Yet, if the trend continues, the ability of authoritarian bodies to combat knowledge with material resources will dwindle to naught, and we may finally enter the age of the philosopher kings.

the method of daryl zero

[In celebration of the 10^th anniversary of Zero Effect]

The similarities between Daryl Zero and Sir A. C. Doyle's iconic detective Sherlock Holmes have been discussed before, at least here, here, here, and here. In particular, there are striking similarities between the principle thematic elements of Zero Effect and those of "A Scandal in Bohemia," the third of the Holmes stories, featuring the sole romantic entanglement of Holmes' career, and a minimal one at that. Likewise, Daryl Zero experiences the sole (seemingly) romantic entanglement of his career, though, admittedly, one much more explicit and serious in character, with Gloria Sullivan.

Holmes disguised as "a drunken-looking groom" in "A Scandal in Bohemia"

The similarities between "A Scandal in Bohemia" and Zero Effect run deeper than general theme, however; in both stories, blackmail, though perhaps justified, is the crime, the blackmailer's secret is revealed during a false fire alarm, a mutual respect emerges between detective and blackmailer, and they meet only while the detective is in disguise (though cunningly identified by blackmailer). When Zero first meets Gloria, he asks her if she is a paramedic; puzzled, she affirms the claim, then asks him how he knew. Zero replies, "I'm very intuitive." Later, we learn, in a typically Holmesian display of "deduction," that it was from the very distinctive smell of iodine that Zero inferred her prior presence in a hospital or ambulance. Likewise, in "A Scandal in Bohemia," Holmes "deduces" that Watson has returned to medical practice from a similar smell:

As to your practice, if a gentleman walks into my rooms smelling of iodoform, with a black mark of nitrate of silver upon his right forefinger, and a bulge on the right side of his top-hat to show where he has secreted his stethoscope, I must be dull, indeed, if I do not pronounce him to be an active member of the medical profession.

There follows a brief discussion of Holmes' method:

I could not help laughing at the ease with which he explained his process of deduction. "When I hear you give your reasons," I remarked, "the thing always appears to me to be so ridiculously simple that I could easily do it myself, though at each successive instance of your reasoning I am baffled until you explain your process. And yet I believe that my eyes are as good as yours."

"Quite so," he answered, lighting a cigarette, and throwing himself down into an armchair. "You see, but you do not observe. The distinction is clear.

We see here two acknowledged cornerstones of Holmes' method: "deduction," and observation. Zero likewise characterizes his method with two principles, the "two obs": observation, and objectivity. Before analyzing the method of Daryl Zero, we would do well to consider Holmes' notion of "deduction."


Typically, a deduction is a truth-preserving procedure, reasoning from true premises to true conclusions. Holmes' "deductions," however, are not truth-preserving; there are many potential explanations for Watson's condition other than his returning to medical practice, perhaps he'd been in another doctor's office and spilled "iodoform" on himself, for instance. Holmes is actually engaging in abductive inference, reasoning backwards from effects to causes. In gross terms, we may even want to call such an inference a "shrewd guess."

Daryl Zero likewise engages in the "shrewd guess" of abductive inference, yet he does not emphasize the inferential step in his method, the "deductive" step, as Holmes would call it. Instead, he emphasizes objectivity, the process by which the relevant facts are sorted from the non-relevant facts. Given that virtually any of the infinitude of facts involved in fully characterizing an event could potentially be relevant to determining the cause of that event, the process of sorting through this infinitude, of zeroing in on that which is relevant, is every bit as crucial to the detective's job as the inferential step.

For example, clever as Zero's inference was from the smell of iodine to Gloria's job as paramedic, it would not have been possible if he had not first identified that smell as a potential clue to her profession (as opposed to her clothes, or demeanor, or the time of day, or any one of an infinitude of factors).

Fluctuations in Zero's ability to remain objective in the selection of pertinent facts correlate with fluctuations in his physical and mental state. When first we encounter Zero, for example, he has been awake for three days, binging on amphetamines. Upon hearing that Gregory Stark is the subject of blackmail, he begins to ruminate upon the fact that "Gregory Stark is the son of a fat man." Zero confirms a few minutes later, as he passes out, that his "abilities are seriously impaired, perhaps even disabled," acknowledging the effect of exhaustion on his ability to objectively sift through the facts and identify those of potential relevance. As it turns out, the obesity of Stark's father is irrelevant to the case.

"Sergio Knight"

Perhaps even more interestingly, we can trace the progression of Zero's romantic interest in Gloria through the lapses in his objectivity. Under working conditions, Zero displays an almost preternatural poise, an uncanny ability to guise himself in the garb of mystery (the ingenious Sergio Knight escapade being only one example), yet in two interactions with Gloria he missteps, failing to perceive a relevant fact, losing his objectivity. The first slip occurs when Gloria asks him if he's in town for "that conference"; reluctantly, Zero agrees. "So you're an accountant?" she asks. He's forced to agree again. However, this encounter takes place after his initial meeting with Gloria, the infamous "are you a paramedic" incident (evidence of slippage on Zero's part itself, needless showing off that could potentially jeopardize his cover (though in this case, perhaps ultimately constructive)), immediately after which the talkative gym receptionist informs him that Gloria is "not married." Zero should have realized that the receptionist's laxity in releasing personal information in the furtherance of romance would make any personal information he had given her (including his profession) potentially available to Gloria Sullivan, a woman already romantically linked with him in the receptionist's mind, as evidenced by the nature of her gossip. If Zero had remained objective, rather than succumbing to distraction in the presence of Gloria's charms, he would have realized that exposing himself to being tagged with a career other than architect, by admitting he was in town for "that conference," in the face of the receptionist's tendency to gossip, would have likewise exposed him to discovery.

Of course, only a preternatural talent such as Zero's could possibly have noticed the relevance between the receptionist's comment and Gloria's question, but it is precisely because he does display such deftness elsewhere that our attention is drawn to this slip. Zero's second slip is less excusable; he fails to take the receipt (after claiming receipt-keeping was "just a matter of habit" for him) as the two leave a restaurant on a date (the very date during which we learn both that Gloria is Stark's daughter and that (possibly?) Zero shares a particular family dysfunction with her - he claims that his father killed his mother, then slit his wrists. Gloria's father, Stark, killed her mother, albeit via an intermediary hitman. Zero looks exposed, honest, as he makes this confession; could this be a legitimate point of emotional contact between them? Or, is he just that good? Has he crafted this story, and delivered it convincingly, as a ploy to trigger her emotions? ~ the monologue indeed comes only after Zero has realized who Gloria is . . . ).


These two slips are noticed by Gloria and provide her with the essential clues to discover Daryl Zero's identity.

Of course, Zero's method must also include an inferential step akin to Holmes' "deduction," but he discusses it, however, only under the description "research":

I can't possibly overstate the importance of good research. Everyone goes through life dropping crumbs; if you can recognize the crumbs, you can trace a path all the way back from your death certificate to the dinner and a movie that resulted in you in the first place. But research is an art, not a science, because anyone who knows what they're doing can find the crumbs—the wheres, whats, and whos—the art is in the whys, the ability to read between the crumbs . . . for every event there is a cause and effect, for every crime a motive, and for every motive a passion. The art of research is the ability to look at the details and see the passion.

The connection here with reasoning backwards from effects to causes is obvious. Yet we also see an emphasis upon analysis of human character and motive. Regardless, the process being described is clearly more inferential than mere "research."

The claim that research is an "art" may at first seem puzzling; for is not the creativity of art somehow at odds with the cold detachment necessary for objectivity? Yet the two are actually entangled, for the exacting standards of objectivity and the true selflessness of great art reach their ultimate embodiment in one and the same faculty.
(I need hardly mention here Holmes' violin or Zero's guitar!)


A similar point was expressed far more eloquently than I ever could by E. A. Poe concerning the relationship between the analytic and the imaginative in the character of the first serialized detective, the enigmatic Auguste Dupin. I leave you with his words:

The analytic power should not be confounded with simple ingenuity; for while the analyst is necessarily ingenious, the ingenious man is often remarkably incapable of analysis. The constructive or combining power, by which ingenuity is usually manifested, and to which the phrenologists (I believe erroneously) have assigned a separate organ, supposing it a primitive faculty, has been so frequently seen in those whose intellect bordered otherwise upon idiocy, as to have attracted general observation among writers on morals. Between ingenuity and the analytic ability there exists a difference far greater, indeed, than that between the fancy and the imagination, but of a character very strictly analogous. It will be found, in fact, that the ingenious are always fanciful, and the truly imaginative never otherwise than analytic.