Oh, I so love this article by Arthur S. Reber! ("How to Differentiate Implicit and Explicit Modes of Acquisition", in Scientific Approaches to Consciousness, Jonathan D. Cohen and Jonathan W. Schooler, eds., Lawrence Erlbaum Associates, 1997).
Listen to this, on differences between" implicit learning" and "explicit learning", or "tacit knowledge" and "explicit knowledge": "Patients with acquired dyslexia reveal virtually normal lexical knowledge of presented words provided they were presented at rates too rapid to be decoded consciously (Coslett, " H. B. ,1986, "Preservation of Lexical Access in Alexia Without Agraphia; Shallice , T. & Saffran, E., 1986, ""Lexical Processing in the Absence of Explicit Word Identification".)" Reber, P. 147).
"Alzheimer's patients performed normally on an implicit sequence learning task but poorly on tasks that required reflection and conscious control of cognition. (Nissen, M. J., & Bullemer, P., 1987, "Attentional Requirements of Learning: Evidence from Performance Measures"." Reber, P. 147. "Large individual differences were found on the explicit process with slow readers taking nearly three times as long as normal readers, but no differences were observed on the implicit task, where slow readers were indistinguishable from normal readers. Aaronson, D, & Scarborough, H. S. , 1977, "Performance Theories for Sentence Coding: Some Quantitative Models"." Reber, P. 148 AND ESPECIALLY!!:
"Two studies have found no significant correlations between performance on implicit learning task and IQ." Reber, A.S., Walkenfeld, F.F. & Hernstadt, R., 1991, " "Implicit and Explicit Learning: Individual Differences and IQ"; Knowlton, B. J. , Ramos, S. J., & Squire, L. R., 1992, "Intact Artificial Grammar Learning in Amnesia: Dissociation of Abstract Knowledge and Memory for Specific Instances"." Reber, P. 148.
All this stuff is really fascinating! But I don't think these empiricists are seeing what is right in front of their eyes: The truth is that "implicit learning" is the only true "cognition". "Explicit learning" is not cognition at all. (There is some kind of wordless structure that we all perceive in the back of our mind." I define "cognition" as CHANGES IN THIS STRUCTURE. "Explicit learning" is merely the ascertaining of knowledge which has been stored by "implicit" learning in the "back of the mind" ( that is in the " Conceptual Structure, "Cognitive Unconscious, " "Adaptive Unconscious," or whatever you want to call it.). This ascertaining can be by means of someone else (such as the author of a book) pointing it out to you; or it can be by means of your own personal observation of the structure.
"Explicit learning" is based on the structure But it does not change it.