original processing episodes. On each training trial, match participants were instructed to memorise a letter string in preparation for a short-term memory test, but they were not told how to memorise that string. It can be inferred from the results that
participants actively adapted to the training task by applying rehearsal processes and organising each “to-be-remembered” string into a series of letter fragments.
Furthermore, it seems likely that they maintained this approach as it was sufficient to meet the demands o f the task which was to select each to-be-remembered string from the list of three strings presented in the second part o f each match trial.
When participants were subsequently presented with more eight-letter strings at test, the format of the strings cued memory for the operations (mental rehearsal) and training string properties (letter fragments) used to process training items. Participants then used their mental rehearsal processing and fragment knowledge to classify the novel test items. Test items containing letter fragments processed during training would be processed more fluently than those containing novel fragments, as familiar fragments would cue prior training episodes whereas novel fragments would not. More fluent processing would be attributed to a test string being grammatical, whereas less fluent processing would be attributed to a test string being ungrammatical. As a result, more LIHA than LILA test strings were classified as grammatical.
While the form of knowledge (letter fragments) acquired by match participants in Experiments 2, 3, and 4 supports the findings of prior AGL studies (e.g., Dienes, Broadbent, & Berry, 1991; Dulany, Carlson & Dewey, 1984; Knowlton & Squire,
1996; Servan-Schreiber & Anderson, 1990), it should not be assumed that this fragment knowledge was acquired in a stimulus-driven manner. In particular, the results of Experiments 2, 3, and 4 challenge an assumption of Servan-Schreiber and Anderson’s (1990) competitive-chunking model that with sufficient training
memorisation leads to encoding whole training items in the form o f hierarchical networks of letter fragments. For example, this model predicts that repeated
encounters with the string GFLK.XDGF will initially result in mental representations of single letters (D, F, G, K, L, and X), progressing to bigrams (GF, LK, XD, and GF), followed by fourgrams (GFLK and XDGF), eventually leading to a representation of the whole string. Thus with fewer training trials participants are expected to encode only letter fragments, but with extended training they are expected to acquire exemplar knowledge.
Counter to the assumptions of the competitive-chunking model, there was no evidence o f whole-item similarity effects with 46 training trials (Knowlton & Squire,
1994, Experiment 2b), 72 training trials (Shanks, Johnstone, & Staggs, 1997 and Experiment 1), or 108 training trials (Experiment 3). Though there was marginal support for whole-items effects with 144 training trials (Experiment 4), this effect could also be due to four-gram fragment knowledge. However, evidence o f four-gram knowledge supports the competitive chunking model as it suggests that participants were acquiring a hierarchy of successively longer letter chunks which with further training would have eventually led to exemplar knowledge.
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Conclusion
In conclusion, there is no evidence that participants can memorise a collection of training exemplars. Where ACS is balanced across similar and dissimilar test items (Experiments 1 and 3; Knowlton & Squire, 1994; Shanks, Johnstone & Staggs, 1997) there is no evidence for whole-item similarity. In Experiment 4, where fourgram ACS was confounded with whole-item similarity, ACS was the stronger predictor o f overall performance. The results of Experiments 1,3, and 4 suggest that exemplar effects reported by Vokey and Brooks (1992) and Whittlesea (1987) were confounded with letter-fragment knowledge.
Chapter 5: Cued Recall and Recognition Measures o f Awareness
As the chance rule-based classification performance of the match groups in Experiments 1 and 2 (Chapter 3) and Shanks, Johnstone, and Staggs (1997, Experiment 4) runs counter to a substantial amount of evidence that memorisation leads to implicit, rule knowledge (e.g., Knowlton & Squire, 1994, 1996; Meulemans & Van der Linden, 1997; Reber, 1967, 1989; Reber & Allen, 1978; Reber & Lewis,
1977), and is o f such crucial significance for the theoretical understanding o f implicit learning, the aims of the experiments reported in this chapter were to examine in more detail the form of knowledge acquired by match participants and to use sensitive tests of awareness o f the knowledge used to classify test items.
In contrast to the lack of support for implicit learning theories, the fragment effects in the classification performance of memorisers in Experiments 2 to 4 provided strong support for the episodic-processing account (Whittlesea, 1997a, b) as it appears that participants met the demands of the match task by “chunking” training strings into two- and three-letter fragments and this fragment knowledge was sufficient to explain classification test performance. It is suggested that biconditional grammar experiments are more likely than finite-state grammar studies to add to our understanding o f the knowledge acquired by incidental learning instructions as rule and fragment knowledge can be tested orthogonally with biconditional but not finite-state grammar generated test strings.
At study by Reber and Allen (1978) illustrates the difficulties o f determining what information participants use to classify test items generated from a finite-state grammar. After observing grammatical training strings, participants correctly
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