Cargo cult reading

Just a reminder that folks ought read with caution arguments of the form

• Vocabulary at 22 months predicts educational attainment;
• Reading to kids can help vocabulary;
• Therefore, read to kids to help them in the long run.

Hey, reading's great. And fun. Ira now recites Where the Wild Things Are back to me, and that's cool. But thinking that moving from not-reading to reading to your kids will ensure outcomes commensurate with those of heavily reading kids is cargo cult thinking.

High IQ folks tend to have lots of books in the house and tend to read to their kids 'cause they enjoy it. They have high IQ kids because of assortative mating and intelligence's heritability. Even if they never read a word to their kids, those parents' kids would probably wind up with pretty decent outcomes just from innate IQ and hearing their parents talking: higher IQ folks have a vocabulary range maybe twice or three times the average. And I know I've seen studies suggesting that, if you control for number of books in the house, the amount of reading a parent does with his kid doesn't have much effect on the kid's outcomes.

So then vocabulary at 22 months may predict educational attainment because they've gotten a taste for reading from their parents, because they've inherited good genes from their parents, or a combination of both. Simply looking at differences in mean educational attainment by differences in mean vocabulary at 22 months doesn't tell you much at all about the effect of reading on educational attainment.

Similarly, sorting kids by income and vocabulary scores tells you little about the effect of income on kids' ability if IQ predicts income and if IQ is heritable.  The report linked above contains this graph:

The report notes that some of the effect is mean reversion, but also points to the different slopes as suggestive of the effects of income.  An entirely plausible alternative reading is that it's reflecting mean reversion to different means.  If it's more likely that high IQ parents have higher income, then a kid from high income parents who tests badly at age 3 is more likely to have had an off day than a kid who presents the same score but who comes from a lower income cohort.

Income may well be doing some of the work here, but ignoring IQ seems a bit odd.  Especially since the Millennium Cohort Study included measures of parental educational achievement, as seen in the study of the effects of prenatal maternal drinking that was also based on MCS data.  Sounds like there's fodder there for a future honours research project.

Cargo coffee cult [updated2]

It's not like I didn't know about cargo cults. The classic story has isolated Pacific Island tribes building things that look like runways after the end of the second world war, hoping that the cargo planes and their wondrous riches will return: it's the belief that the trappings of an activity are what brings the benefits. And, you can see how they'd made the mistake: folks built runways, and all of a sudden the planes came. Maybe making more offerings of runways and hangars will bring them back after they leave.

And so it was with our departmental coffee machine. Push button, coffee arrives. It says empty grounds, we empty grounds. Then push button, coffee arrives. That stopped working early last week. After emptying grounds, the machine wouldn't recognize that we'd emptied the grounds and refused to deliver coffee. So we tried cleaning around inside the machine, thinking that some sensor or other up in there must be dirty. And, sometimes it worked! But not always. And so we developed more and more elaborate rituals, trying to make the coffee return. But whenever we thought we'd found the trick, it stopped working again.

The repair guy today tells us that there's a not uncommon electrical fault with the machine. If you leave the grounds tray out of the machine for long enough, it resets itself. So the lengthy cleaning sessions worked, not because we'd found the bit that needed cleaning but because the tray had been left out long enough. And just going back afterwards to clean the particular bit found later would never work because the tray hadn't been left out long enough. We can either spend $500 fixing the machine, or just leave the tray out for 5-10 minutes after dumping the grounds. We've opted for the latter.

Off now to perform the morning ritual...push button, wait for coffee, offer homage unto the machine. Next time it stops working, I'll perhaps weave a little wicker coffee cup to put beside the machine to encourage it.

Update: I'd forgotten how much worse that machine's coffee is compared to the stuff I've been buying at the shoppe downstairs. Sigh.

Further Update: Perhaps if I leave gold coins beside the machine, it'll make better coffee. I give money downstairs to get better coffee...