Do you think you could link to that paper?
A Larger vs. smaller cities comparison sounds like it has ample room for confounding factors, no?
The other outcomes attributed to lead sound like they correlate with crime rates, so this isn't independent evidence for the lead hypothesis.
I think the paper that I looked at was The Answer is Lead Poisoning. Mainly just looking at the graphs & tables.
The city size pattern is not a unique prediction of the lead hypothesis (there are various other differences between large & small cities which could account for it, though nothing that strikes me as overwhelmingly obvious), but it is a relatively unambiguous prediction (especially if there's high quality data on city size vs. environmental lead levels - I'm not sure how good those data are). If large vs. small cities turned out not to have this difference in crime trends then that would be pretty strong evidence against the lead hypothesis, so the fact that the comparison did come out this way must be at least some evidence in favor of the lead hypothesis.
He refers to this graph, but not any of the research on the various other predictions that you could derive from the hypothesis that lead caused much of the hump in crime over the past 60 years.
Can you name some of these predictions? Can you link to some of the research? What exactly are you referring to?
3 predictions that I came up with, when I heard about the hypothesis:
I looked at one of Nevin's papers shortly after the Drum piece originally came out and it had some evidence for all 3 predictions, though not with as much rigor/precision/detail as I would've liked. For example, on prediction #3 it compared larger cities (which had more driving per unit area, and thus more environmental lead due to gasoline) to smaller cities and showed that their crime rates matched this pattern.
There is also research on other steps in the long chain (e.g., measuring blood levels of lead), and on other outcomes attributed to lead (e.g., teen pregnancy rates), some of which is mentioned in Drum's original piece. I haven't looked into that research beyond what I've seen in the popular press articles.
Meh, probably not:
http://stevenpinker.com/files/pinker/files/pinker_comments_on_lead_removal_and_declining_crime.pdf
There are reasons to be skeptical of any claim based on correlations between such widely separated variables as lead exposure (the cause) and crime (the effect). Consuming lead does not instantly turn someone into a criminal in the way that consuming vitamin C cures scurvy. It affects the child’s developing brain, which makes the child duller and more impulsive, which, in some children, and under the right circumstances, leads them to grow up to make short-sighted and risky choices, which, in some children and under the right circumstances, leads them to commit crimes, which, if enough young people act in the same way and at the same time, affects the crime rate. The lead hypothesis correlates the first and last link in this chain, but it would be more convincing if there were evidence about the intervening links. Such correlations should be far stronger than the one they report: presumably most kids with lead are more impulsive, whereas only a minority of impulsive young adults commit crimes. If they are right we should see very strong changes in IQ, school achievement, impulsiveness, childhood aggressiveness, lack of conscientiousness (one of the “Big Five” personality traits) that mirror the trends in lead exposure, with a suitable time delay. Those trends should be much stronger than the time-lagged correlation of lead with crime itself, which is only indirectly related to impulsiveness, an effect that is necessarily diluted by other causes such as policing and incarceration. I am skeptical that such trends exist, though I may not be aware of such studies.
...
Also, the parallelism in curves for lead and time-shifted crime seem too good to be true, since the lead hypothesis assumes that the effects of lead exposure are greatest in childhood. But 23 years after the first lower-lead cohort, only a small fraction of the crime-prone cohort should be lead-free; there are still all those lead-laden young adults who have many years of crime ahead of them. Only gradually should the crime-prone demographic sector be increasingly populated by lead-free kids. The time-shifted curve for crime should be an attenuated, smeared version of the curve for lead, not a perfect copy of it. Also, the effects of age on crime are not sharply peaked, with a spike around the 23rd birthday, and a sharp falloff—it’s a very gentle bulge spread out over the 15-30 age range. So you would not expect such a perfect time-shifted overlap as you might, for example, for first-grade reading performance, where the measurement is so restricted in time.
Finally, the most general reason for skepticism about a causal hypothesis based on epidemiological correlations between a widely separated cause and effect is that across times and places, many things tend to go together. Neighborhoods next to smoggy freeways also tend to be poorer, more poorly policed, more poorly schooled, less stable, more dependent on contraband economies, and so on. It’s all too easy to find spurious correlations in this tangle – which is why so many epidemiological studies of the cause and prevention of disease (this gives you cancer; that prevents it) fail to replicate.
It sounds like Pinker is unfamiliar with most of the research on the topic. He refers to this graph, but not any of the research on the various other predictions that you could derive from the hypothesis that lead caused much of the hump in crime over the past 60 years.
The things that he says about priors, and about the sorts of research that he'd like to see, sound plausible, but I wouldn't put much stock in what he says about the state of the research.
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It seems that the problem with Tom "Voldemort" Riddle is that, although he was ambitious, he had no ambition. He was Sorted into Slytherin, and was driven by fear and cleverness to grasp at any opportunity for advancement which he could imagine. But there was no great ambition that he was driven to accomplish - at best he could grasp his way upward into the role of a hero, or a Dark Lord, or into personal immortality, or some other position of merely personal success, never breaking the bounds of his own lonely existence.
True ambition was the power that he knew not, and his downfall.
Wizards seem to be overly skeptical of the information that they get from their magical detection spells, an analogue to what some muggle scientists call algorithm aversion. (As evidenced by the current confusion about Hermione's nature, and the lack of response when the wards previously identified The Defense Professor as her killer.)
This means that scheming wizards who want their plots to go undiscovered don't need to trick the magical detection spells, they just need to pursue strange enough plots so that other wizards won't believe what the detection spells tell them. Which makes Voldemort's creative uses of magic analogous to Dumbledore's ploy of pretending to be crazy.
The stage seems to be set for a sequel adventure series, The Three Immortals. Three great heroes, each blessed with a fragment of immortality, work together to fend off the forces of destruction and bring true immortality to all of humanity.
Unicorn Girl, filled with the life-giving, regenerative powers of two noble magical creatures. Her mind captures everything that she sees, with amazing fidelity, while the purity of her heart pulls her to do what's right with similar fidelity. Some call her "mudblood", in honor of the ancient myths about the creation of man from earth, because the power to re-create herself flows continuously through her veins.
Mr. Physics, the culmination of the great Peverall line which has sought immortality for generations, is the heir to many great and powerful magical artifacts. But it is his deep and detailed knowledge of the laws of the universe which grants him his greatest power - the power to make anything out of anything, even reshaping his own body. He has made a solemn vow to protect humanity, with Unicorn Girl as his moral compass.
The mysterious Cloud has dark secrets which are hidden even from himself, but his mind still holds a wealth of ancient lore to share and an intellect so sharp it can cut through any facade or riddle... except perhaps his own past. This great mind is backed up, a hundred times over, in a vast network which allows him to be reborn in full force should his body ever fail him. The first to reach immortality, Cloud helped bring both his companions into their powers.
I cannot for a second imagine Moody allowing Harry to hold on to Tom Riddle. There are too many ways in which keeping a superpowered, immortal amnesiac former villain on your person could go wrong. Harry must anticipate this, so can't consult Moody.
Perhaps. But Moody did defer to Dumbledore, keeping Moody totally in the dark doesn't seem like a plausible option, and Harry explained to McGonagall in chapter 14 that he had enough common sense to seek out the appropriate experts in situations like this (or discovering Salazar's Chamber).
A couple guesses about scenes that might be coming:
Harry has a (mostly) honest conversation with Moody about what happened to Voldemort, with an eye to adding more safeguards. They consult with the world's foremost expert on memory-charming powerful wizards into insignificance, Gilderoy Lockhart.
Hermione is determined to rescue Dumbledore from the Mirror, and a phoenix comes to her because of it.
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Suppose you're Bayesian, and you're calculating
P(lead causes crime | data) = P(data | lead causes crime) * P(lead causes crime) / P(data).
What Pinker is saying is that P(data | lead causes crime) is not as high as you'd think, because if lead really does cause crime, we should not expect the crime curve to be a time-shifted version of the lead curve. It's probably still true that P(data | lead causes crime) > P(data), so that you should update in the direction of lead causes crime, but this update should probably be smaller than you thought before reading that paragraph.
Has anyone figured out what crime curve you would expect based on the lead curve (presumably a version that is shifted & smeared out based on the age distribution of criminals), and checked how well it fits the actual crime data? It's not obvious to me, from looking at the pictures that I've seen with the shifted curves, that adding the smearing would make the fit worse. For instance, the graph I linked earlier shows that the recent drop in crime is more gradual than the drop in lead that happened 20-30 years ago, which seems to fit the more rigorous "time-shifted and smeared out" prediction better than it fits the simplistic time-shifted curve approach that Nevin used.