We know that surveying teenagers about alcohol, drugs and sex makes them more likely to report that they have drunk, taken drugs and had sex in future surveys.

The question is we're they lying the first time, the 2nd time or did their behaviour actually change.

I've never wondered until now wtf is infant-directed song?

That table also answers the question I was asking all the way through, "How do you know whether they lost singing to infants or never had it?" They split off from the Southern Ache, who still do it.