Now, we have two ways of interpreting this outcome: the fatalistic and the optimistic.
The fatalistic interpretationA fatalist will say that it is proof positive of the existence of talent, and that those who do not have this talent are doomed to failure at learning languages.
The optimistic interpretationThe optimistic interpretation is to say that the successful learners are succeeding despite the teaching, and that this study is, by shedding new light on what the successful learners actually do, showing what teachers should be doing if they want to be successful.
"Rules" are a bit out of fashion in language teaching. I've always said that this is because people have been teaching incorrect rules, rather than that rules are inherently unsuited to language teaching. A linguistic "rule" is (or should be, at least) nothing more than an observed pattern emerging from real usage. If successful learners are those who can identify patterns, then we must assume that after identifying these patterns, they learn them.
So I would suggest that the logical conclusion is that we should be teaching these patterns to students, rather than relying on them identifying them.
An example patternWhen I was learning French (my first foreign language) at high school, I noticed the distinction between the "long conjugations" and the "short conjugations" of the present tense (the long conjugations are the nous and vous forms, and the short conjugations are the rest), and I noticed that in irregular verbs, these forms were almost always regular. (Is there any verb other than être that has irregular long conjugations?)
So while my classmates were attempting to memorise the irregular verb tables by rote, I was saving myself time and effort by only memorising the conjugations that didn't arise out of bog standard, regular conjugation.
Now it could be that the advocates of the discovery method are right, and that part of my success was down to the fact that I worked this out for myself, but I doubt it. And even if that's true, is it fair to trade off the success of the majority against the success of a lucky few? It is obvious that being told this would have reduced the effort required by my classmates to learn their irregular verbs.
Teaching patterns vs teaching rulesThe problem with most of the "rules" traditionally presented in grammar books is that they are more strictly ranked and regimented than they are in real life. Real patterns in real language can't be so neatly packaged by tense.
Take one of the patterns in Spanish taught by Michel Thomas:
The third person plural conjugation of a verb is the third person singular conjugation plus N, except in the preterite.
Now that's not how he taught it, but that's the concise description. When he taught it, he simply used it in the present, and then got the students to apply it in the other tenses.
One of the reasons some people don't like this pattern is that "except" bit, but this really isn't a problem, because the pattern also holds for the second person singular: third singular +S, except (again) in the preterite.
It's regular, it's predictable. Even the "exception" is regular in that it's an exception for both 2S and 3P.
This is the sort of pattern that I suspect all those successful learners are finding, and this is the sort of pattern that made Thomas such an effective teacher.
So let's find those patterns, and let's teach them.