The most important research on learning I’ve read

Someone has posted it on line, so here it is !

Deferred Feedback Sharply Dissociates Implicit and Explicit Category Learning
J. David Smith, Joseph Boomer, Alexandria C. Zakrzewski, Jessica L. Roeder, Barbara A. Church, and F. Gregory Ashby  Psychological Science 2014, Vol. 25(2) 447-457

I’ve been mulling this article since the summer of 2014, when it was published. It’s life altering.

Unfortunately, if you’re not in the field, reading the study isn’t easy. The press release is intelligible but brief. 

For the moment, the thing to know is that this study probably proves, finally, that we have two separate and distinct learning systems inside our brains.

Psychologists and cognitive scientists have been talking about “dual systems” and “dual systems theory” forever, but no one had nailed it down. Now they have.

The two systems are separate and distinct in the sense that if you turn one system “off” the other still learns. They’re “dissociable.” 

And: the 2 systems learn differently.

“Deferred feedback” looks at category-learning, but as far as I can tell these two systems learn everything, including physical skills. 
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Compare and contrast

The chart below is correct (I believe), but it says nothing about the relationship between the two learning systems–which no one seems to understand yet. 

So, while I’ve put “vocabulary” under explicit learning, I’m fairly sure vocabulary can also be picked up via implicit learning. 

And given what I’ve seen in the L2 literature about grammar learning, it seems clear that some explicit learning helps with grammar, too–at least, with the kind of grammar you use in formal writing, as well as with learning the grammar of a second language.

Obviously, no one learns the conversational grammar of his or her native language at school. 

In short, the two systems seem both to compete and to support each other in some way no one has worked out. [update 1/14/2019: Yes, the 2 systems compete.]
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Information-integration learning	Rule-based learning
“Life” learning	“School” learning
Unconscious	Conscious
Implicit learning: you can’t necessarily put what you’ve learned in words (& if you can, words come to you later)	Explicit learning: you can put what you’ve learned in words
Intuition, everyday categories (good versus bad, dog versus cat), social rules, habit	Formal concepts, theories, disciplines, etc.
Grammar	Vocabulary
Learns relatively slowly	Learns quickly
Can’t learn “offline” (learning stops after a “lesson” is over)	Can learn “offline” (learning continues after a lesson is over)
Must have immediate feedback – students must know whether their answer was right or wrong after each answer or no learning occurs	Can learn with delayed feedback – students can get their tests back days later and still learn from their mistakes)
Can learn several things at the same time (e.g.: can learn the orientation and the width of a visual stimulus)	Can learn just one thing at a time (can learn the orientation or the width of a stimulus, but not both at the same time)

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From the abstract:

Deferred reinforcement qualitatively eliminated implicit, information-integration category learning. It left intact explicit, rule-based category learning.

And see:
System 1 and System 2 compete