Gotcha, Cucaracha

Last night I was singing “La cucaracha” while I gave Doug a bath. I was pronouncing the r with the Spanish pronunciation. This sound is often referred to as the tap or flap, and we also have it in English: It is the same sound you make for the t in atom, or the d in Adam. (It sounds a lot like a [d], but it’s not—try making a careful [d] sound in Adam, and it will sound strange.) I’ll transcribe this sound as D, so I was singing:

(1) La cucaDacha, la cucaDacha!

Doug starts singing it, too, but like this, with a regular, plain old English [r]:

(2) La cucaracha, la cucaracha!

Now why did he do that? If he were reading the word, I would expect him to pronounce the r as [r], but he’s never seen this word written! All he had to go on was what he heard me say, and he heard me saying [D]. Doug has been making the flap sound for years in dozens of ordinary English words (including his brother’s name, Adam), so why should he suddenly turn this one into an [r]? I mean, suppose Doug had heard me say some unfamiliar English word that contained a flap, such as adage. Would he repeat it as arage? I can’t imagine he would.
There is, however, one difference between the flap in English words such as Adam the and the flap in Spanish words such as cucaracha. In English, the flap always occurs after a stressed syllable and before an unstressed one. For example, if we write out Adam with D indicating the flap and boldface underline indicating the stressed syllable, we get ADam. But doing the same thing with cucaracha, we get cucaDacha. So maybe Doug was picking up on the difference in stress. I tried an experiment with just the cara part of the word:

Me: Say caDa
Doug: caDa
Me: Say caDa
Doug: cara

How about that? He’s got the English flap rule well-internalized … as of course he should, being a native speaker of English. I’ll have to try a few other nonsense syllables with flaps in them to see what he does.