Amnesia, Memory, and the Implicit/Explicit Learning Distinction

Amnesia, Memory, and the Implicit/Explicit Learning Distinction J. Brendan Ritchie (SENECA.Y@Gmail.Com) Department of Philosophy, 453 University College Winnipeg, MB, R3T 2M8 Canada David Shanks and colleagues (Shanks & St. John 1994; Kinder & Shanks 2001, 2003). In the remains of this paper I take up the arguments and results of Shanks and Mark St. John (1994), as well as Shanks’ work with Annette Kinder (2001, 2003). I will argue such research fails to show the irrelevance of results from studies of amnesiacs. While not the only researchers to be critical of multi-model theories of learning and memory (e.g. see Roediger 1990) the work of Shanks and others is especially relevant. This is because in the case of Kinder & Shanks they focus solely on amnesia and implicit learning, rather than implicit forms of learning and memory, and, in the case of Shanks & St. John are widely cited, so it is important to see where their arguments fail. Abstract Whether or not a disassociation between implicit and explicit learning can be proven experimentally has been widely contested. In this paper I am concerned with the arguments that David Shanks and colleagues have made for why results from work on amnesia are: (a) not relevant to the debate (Shanks & St. John, 1994), and (b) can be simulated by connectionist models that do not involve distinct learning systems (Kinder & Shanks, 2001, 2003): making amnesia irrelevant. None of the arguments that Shanks and colleagues make succeed at proving either (a) or (b). Keywords: amnesia; implicit learning; explicit learning episodic memory; disassociation; connectionism; hippocampus. Background Since Reber (1967) first used the term ‘implicit learning’ there has been much debate as to whether or not a distinction can be shown between implicit and explicit forms of learning: this being especially true of the last 15 or so years (Shanks Naturally, various methods have been used to try and prove the case, both for and against, the implicit/explicit learning distinction. Especially common, for example, are the Artificial Grammar Learning (AGL) experiments first conducted by Reber (1967). Reber had subjects study seemingly nonsense letter strings, such as VXVS, and then told them that the strings were constructed using a set of rules. The subjects were then informed that in the next stage of the experiment they would have to try and determine which strings were grammatical, and which were not. Subjects displayed an above chance ability for identifying grammatical letter strings, but could not report what the grammatical rules were. Thus, it was concluded, the rules had been learned implicitly. Such work, however, is far from conclusive. For instance, Perruchet & Pacteau (1990) found that subjects are successful at determining which strings are grammatical if they only study letter pairs, such as VX, and not full letter strings. If this is right, then it is mistaken to expect subjects to report rules, since knowledge of pairs is enough for determining which strings are grammatical. The hypothesis being that learning letter pairs caused the desired results, which subjects can report familiarity with, rather than implicitly learned rules. Despite such difficulties many researchers (e.g. Knowlton, Ramus & Squire, 1992) think that methods like AGL experiments can overcome such difficulties by using amnesiacs in the place of normal subjects. In light of this, whether studies of amnesiacs provide any novel defense of the implicit/explicit learning distinction has been questioned. Especially prominent in this regard has been the work of The Irrelevance of Amnesia This section is split into two parts: part one responds to the target article of Shanks & St. John (1994) who argue that evidence from work on amnesia is undermined by the fact that some amnesiacs suffer from only partial deficits to explicit learning. Part two objects to the arguments made in response to commentary on Shanks & St. John (1994). Implicit Learning and Implicit Retrieval According to Shanks & St. John implicit learning occurs if there is (i) learning that is not accompanied with awareness of the information being learned, and (ii) a separate system from the one that operates during more common forms of learning (1994: 368). In contrast, implicit retrieval is retrieval where the information from a past experience is recalled and influences current processing without conscious recall of the prior experience (Shanks & St. John, 1994: 372). 1 Shanks & St. John hold that, while a case of implicit learning entails the occurrence of implicit retrieval, it is not the case that implicit retrieval entails implicit learning. As an example, suppose a subject emits a galvanic skin response (GSR) in response to a conditioning stimulus (CS): a tone; the CS previously being paired with an unconditioned stimulus (US): a shock. When the subject emits the GSR, one of three things might have occurred: 1. The subject is able to explicitly recall the study episode: the subject can verbally report or somehow show evidence of recalling the study episode. Perhaps the subject remembers where the shock was administered, or from where the tone was being emitted. This would fail to be a case of implicit retrieval, since the subject can consciously recall the study episode. This definition follows that of Schacter (1987).