The weakness of autodidactic learning, by the way, is that you only see the weaknesses or deficiencies in your learning that YOU can observe.
As Jon pointed out-- this means that some of those deficiencies will go unaddressed-- because being human means that we all have blind spots that are driven by our perceptions and emotions.
Autodidacts may well see their learning as "perfect" because it is, at least within the construct of their own perceptions about the subject. You can't know what you don't know, in other words.
Developing autodidactic learning strategies in young students has to involve a lot of cautions about comparing sources of information, critical evaluation of information, bias analysis, etc. etc. Again, there is development in play there, in a lot of cases. I'm a far better autodidact NOW than I was in my early 20's, and the reason is that I have set aside my confidence in my understanding, and generally operate on the assumption that I do not have an expert grasp on the subject, and could always learn MORE that I haven't thought about. I set things down, of course, when I'm done learning about them, but always with the idea that there is a "maybe later" aspect to those things, that it isn't static, and is subject to additional input.
Now, learning from a teacher doesn't guarantee a BETTER outcome, by any means, but it does mean fewer gaps, assuming that student and teacher are not identical in world-view and perceptions. The more teachers, the better, in fact. Sources which disagree or emphasize different aspects of a field are quite helpful. The reason is that the teachers see some gaps as worthy of addressing, and hopefully the student will perceive others and seek clarification.
This is the idea behind peer review in publications. More eyes is a good thing, because it improves the whole by reducing the gaps. Similarly-- advanced degrees are awarded by COMMITTEES of experts, not by a single person.
This is the single lens through which spiraling makes sense to me, actually-- it improves student learning to force slightly different perspectives on the same material, and provides opportunity to learn using less familiar/comfortable modalities.
It's still stultifying for highly capable learners, however. It sure works a treat for those at the other end of the distribution, though.
