The role of similarity in artificial grammar learning.

The authors examine the role of similarity in artificial grammar learning (AGL; A. S. Reber, 1989). A standard finite-state language was used to create stimuli that were arrangements of embedded geometric shapes (Experiment 1), connected lines (Experiment 2), and sequences of shapes (Experiment 3). Main effects for well-known predictors from the literature (grammaticality, associative global and anchor chunk strength, novel global and anchor chunk strength, length of items, and edit distance) were observed, thus replicating previous work. However, the authors extend previous research by using a widely known similarity-based exemplar model of categorization (the generalized context model; R. M. Nosofsky, 1989) to fit grammaticality judgments, by nested regression analyses. The results suggest that any explanation of AGL that is based on the existing theories is incomplete without a similarity process as well. Also, the results provide a foundation for further interpreting AGL in the wider context of categorization research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theories of artificial grammar learning.

Artificial grammar learning (AGL) is one of the most commonly used paradigms for the study of implicit learning and the contrast between rules, similarity, and associative learning. Despite five decades of extensive research, however, a satisfactory theoretical consensus has not been forthcoming. Theoretical accounts of AGL are reviewed, together with relevant human experimental and neuroscience data. The author concludes that satisfactory understanding of AGL requires (a) an understanding of implicit knowledge as knowledge that is not consciously activated at the time of a cognitive operation; this could be because the corresponding representations are impoverished or they cannot be concurrently supported in working memory with other representations or operations, and (b) adopting a frequency-independent view of rule knowledge and contrasting rule knowledge with specific similarity and associative learning (co-occurrence) knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative chunk strength in artificial grammar learning.

In 4 experiments, adherence to grammatical rules and associative chunk strength (including different measures, each calculated on the basis of the frequency with which bigrams and trigrams present in the test strings appeared in the learning strings) were manipulated independently in the test phase of an artificial grammar learning task. When participants learned few items of the grammar (Experiments 1A and 2A), the associated items were more often classified as grammatical than the nonassociated ones. On the other hand, when the learning phase included most of the grammatical items (Experiments 1B and 2B), the only effect observed was an effect of grammaticality. These results suggest that, depending on the specific constraints of the tasks, knowledge based on bigrams and trigrams and knowledge based on the abstraction of the grammatical structure can be used for the classification task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two modes of transfer in artificial grammar learning.

Participants can transfer grammatical knowledge acquired implicitly in 1 vocabulary to new sequences instantiated in both the same and a novel vocabulary. Two principal theories have been advanced to account for these effects. One suggests that sequential dependencies form the basis for cross-domain transfer (e.g., Z. Dienes et al, see record 1999-13687-003). Another argues that a form of episodic memory known as abstract analogy is sufficient (e.g., L. R. Brooks & J. R. Vokey, see record 1992-00385-001). Three experiments reveal the contributions of the 2. In Experiment 1 sequential dependencies form the only basis for transfer. Experiment 2 demonstrates that this process is impaired by a change in the distributional properties of the language. Experiment 3 demonstrates that abstract analogy of repetition structure is relatively immune to such a change. These findings inform theories of artificial grammar learning and the transfer of grammatical knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The architecture of intuition: Fluency and affect determine intuitive judgments of semantic and visual coherence and judgments of grammaticality in artificial grammar learning.

People can intuitively detect whether a word triad has a common remote associate (coherent) or does not have one (incoherent) before and independently of actually retrieving the common associate. The authors argue that semantic coherence increases the processing fluency for coherent triads and that this increased fluency triggers a brief and subtle positive affect, which is the experiential basis of these intuitions. In a series of 11 experiments with 3 different fluency manipulations (figure-ground contrast, repeated exposure, and subliminal visual priming) and 3 different affect inductions (short-timed facial feedback, subliminal facial priming, and affect-laden word triads), high fluency and positive affect independently and additively increased the probability that triads would be judged as coherent, irrespective of actual coherence. The authors could equalize and even reverse coherence judgments (i.e., incoherent triads were judged to be coherent more frequently than were coherent triads). When explicitly instructed, participants were unable to correct their judgments for the influence of affect, although they were aware of the manipulation. The impact of fluency and affect was also generalized to intuitions of visual coherence and intuitions of grammaticality in an artificial grammar learning paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer in artificial grammar learning: A reevaluation.

This article covers methodological and theoretical issues in artificial grammar learning. Arguments that such tasks are mediated by abstract knowledge (e.g., A. S. Reber, see record 1991-00330-001) are based primarily on evidence from transfer experiments, where the surface vocabulary is changed between learning and test items. Because of a number of methodological concerns, the small magnitudes of artificial grammar learning effects generally are difficult to interpret. Possible solutions are offered here. Furthermore, even reliable transfer effects imply neither that subjects have acquired abstract knowledge of the underlying grammar nor that they are performing a process of abstract analogy from memorized whole exemplars. Models that learn only surface fragments of the training stimuli and perform abstraction at test rather than during learning are wholly consistent with transfer phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The information acquired during artificial grammar learning.

In an artificial grammar learning task, amnesic patients classified test items as well as normal Ss did. Item similarity did not affect grammaticality judgments when similar and nonsimilar test items were balanced for the frequency with which bigrams and trigrams (chunks) that appeared in the training set also appeared in the test items. Amnesic Ss performed like normal Ss. Results suggest that concrete information about letter chunks can influence grammaticality judgments and that this information is acquired implicitly. The similarity of whole test items to training items does not appear to affect grammaticality judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Independent judgment-linked and motor-linked forms of artificial grammar learning

Actinosporean infection of the oligochaete fauna living in the mud and on the vegetation of fish ponds used for rearing common carp in polyculture was studied during a one-year survey at a fish farm in Hungary, located south of Budapest. Twenty-eight actinospore types were isolated from the oligochaetes Tubifex tubifex, Branchiura a sowerbyi, Limnodrilus hoffmeisteri, Nais elinguis, and Stylaria lacustris collected during the survey, which could be classified into the triactinomyxon, raabeia, aurantiactinomyxon and neoactinomyxon groups. Drawings depicting individual actinospore types are presented on plates and their characteristic dimensions have been summarised in tables. The prevalence and seasonality of actinosporean infections observed in the various oligochaete species have been illustrated graphically. Infection by actinospores showed a pronounced seasonality. In the spring, summer and autumn the prevalence of raabeia infection in Branchiura exceeded 90%, while in the winter it dropped to 42%. A similar phenomenon could be observed for aurantiactinomyxon infection, while neoactinomyxon infection reached its peak in the autumn. In Tubifex, Limnodrilus, Nais and Stylaria species the peak of actinosporean infection occurred, with minor differences, in the spring and summer. Actinosporean infection in the individual Oligochaeta species showed much higher prevalence values than had been reported in the literature, which can be explained by the novelty of the examination technique used. It cannot be decided with absolute certainty which myxosporean developmental stage the different actinospore types described during this survey represent of the species of Myxosporea parasitic in the given ponds. This would require an experimental study for which the data presented here may serve as a basis.     

Transfer in artificial grammar learning: The role of repetition information.

In this article, the authors report 2 experiments that investigated the sources of information used in transfer and nontransfer tasks in artificial grammar learning. Multiple regression analyses indicated that 2 types of information about repeating elements were crucial for performance in both tasks: information about the repetition of adjacent elements and information about repetition of elements in the whole item. Similarity of test items to specific training items and chunk information influenced participants' judgments only in nontransfer tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Indirect effects of synthetic grammar learning in an identification task.

Two experiments investigated the effects of incidental learning of an artificial grammar on an indirect measure. Ss memorized consonant strings and later identified these in a perceptual clarification procedure. The competitive chunking model by E. Servan-Schreiber and J. R. Anderson (see record 1990-27513-001) predicted faster identifications of grammatical as opposed to nongrammatical strings. Both experiments confirmed this prediction. Exp 2 further investigated whether faster identification induces a feeling of familiarity, which should increase the probability of subjects responding "grammatical" to a string. Faster identifications were indeed related to "old" responses in a recognition judgment. However, there was no systematic relation between speed of identification and grammaticality judgments, which is inconsistent with the prediction of the competitive chunking model that familiarity exclusively mediates grammaticality judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Observational learning and the effects of model-observer similarity.

This study examined the effects of similarity in competence between model and observer on the effectiveness of observational learning in argumentative writing. Participants ( N=214, 8th grade, mixed ability) were assigned to 1 of 3 conditions: an observation/weak-focus, an observation/good-focus, or a control condition. The two observational-learning groups observed pairs of peer models performing writing tasks. Participants focused respectively on the noncompetent (weak) model or on the competent (good) model. The control group performed the writing tasks themselves. Results are consistent with the similarity hypothesis: Weak learners learn more from focusing their observations on weak models, whereas better learners learn more from focusing on good models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beyond dissociation logic: Evidence for controlled and automatic influences in artificial grammar learning.

Evidence for unconscious learning has typically been based on dissociations between direct and indirect tests of learning. Because of some inherent problems with dissociation logic, we applied the logic of opposition to 2 artificial grammar learning experiments. In Experiment 1, participants were exposed to 2 different sets of letter strings, generated from 2 different grammars, and later rated test strings for grammaticality with either in-concert (rate grammatical strings consistent with either structure) or opposition (rate grammatical only strings from 1 of the structures) instructions. Manipulating response deadline affected controlled, but not automatic influences. In Experiment 2, after similar training, a source-monitoring test was administered from which the in-concert and opposition conditions were derived. The test indicated that varying the retention interval affected controlled, but not automatic, influences. The results are discussed in terms of awareness, knowledge representation, and metacognitive processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chunks are not enough: The insufficiency of feature frequency-based explanations of artificial grammar learning.

Two experiments with a total of 104 undergraduates tested chunk frequency explanations of artificial grammar learning, which hold that classification performance is dependent on some metric derived from the frequency with which certain features occur within the letter string stimuli. Exp 1 revealed that classification performance was affected by close graphemic similarity between specific training (e.g., MXRVXT) and test strings (e.g., MXRMXT), despite the fact that similar strings did not contain frequently occurring features (e.g., bigrams or trigrams). This effect was replicated in Exp 2a, and Exp 2b demonstrated that substituting letters to make the consonant strings pronounceable (e.g., substituting X, R, and T, in the consonant string MXRMXT with Y, A, I, to produce MYAMYI) affected classification performance, despite the fact that objective measures of feature frequency were not altered. It is argued that models of classification that focus entirely on the frequency of features within the literal stimulus are insufficient, and that some allowance must be made for how the stimulus is encoded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations among implicit and explicit memory tasks: The role of stimulus similarity.

Compares the effect of picture fragmentation level at study on performance on a variety of implicit and explicit memory tests. Consistent with previous research, a moderately fragmented study picture produced the most learning on the implicit memory task of picture fragment completion (Exp 1) and speeded picture identification (Exp 4). In contrast, an intact study picture produced the most learning on the implicit memory task of naming intact pictures (Exp 3). These results suggest that performance on 2 implicit memory tasks can be dissociated by differences in visual similarity between the study and test forms of a stimulus. More surprising, parallel effects were observed in recognition memory. Recognition memory was best when fragmentation levels of the study and test pictures matched (Exp 2) or were comparable (Exp 1). In contrast to many results in the literature, recognition memory was acutely sensitive to surface form differences. The results are discussed in terms of 2 types of study-test similarity, stimulus similarity and process similarity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The transfer effect in artificial grammar learning: Reappraising the evidence on the transfer of sequential dependencies.

Exposure to sequences of elements generated by an artificial grammar enables observers to classify new sequences presented either with the same (within-domain) or different (across-domain) vocabulary elements as being well- or ill-formed according to that grammar (A. S. Reber, 1969). Experiment 1 replicated G. T. M. Altmann, Z. Dienes, and A. Goode's (1995) demonstration of this effect, but inspection of hits and correct rejections revealed that a single cue was used to reject a subset of the ungrammatical sequences. Experiment 2 removed this cue, and participants no longer discriminated between grammatical and ungrammatical sequences in the novel domain. The authors conclude that G. T. M. Altmann et al.'s demonstration of discrimination in the novel domain did not necessitate the application of knowledge pertaining to sequential dependencies. Implications of the data for other studies, showing abstraction of knowledge across test sequences, are also considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations between medial prefrontal cortical subregions in the modulation of learning and action.

The medial prefrontal cortex (mPFC) has been implicated in various attentional functions. This experiment examined the involvement of mPFC subregions in the allocation of attention in learning and action as a function of the predictive accuracy of cues. Rats with dorsal (encompassing anterior cingulate, prelimbic, and infralimbic cortices) or ventral (encompassing mainly infralimbic and dorsopeduncular cortices and tenia tecta) mPFC lesions were trained in a multiple-choice discrimination task in which operant nosepoke responses to some visual cues were consistently (100%) reinforced (CRF) with food, whereas responses to other visual cues were partially (50%) reinforced (PRF). In challenge tests designed to assess attention in the control of action, responding was directed more to CRF cues than to PRF cues in sham and dorsal mPFC-lesioned rats, but ventral mPFC-lesioned rats showed similar levels of responding to both CRF and PRF cues. Nevertheless, when given a choice between simultaneously presented CRF and PRF cues in a cue competition test, all groups responded more to CRF cues. In a subsequent Pavlovian overshadowing phase designed to assess attention in the acquisition of new learning, previously trained CRF cues overshadowed conditioning to novel auditory cues more than did PRF cues in dorsal mPFC-lesioned rats, whereas the opposite pattern was observed in sham and ventral mPFC-lesioned rats. These results suggest a dissociation within the mPFC in the use of reinforcement prediction information to allocate attention for new learning and for the control of action. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Abstractness of implicit grammar knowledge: Comments on Perruchet and Pacteau's analysis of synthetic grammar learning.

On the basis of 3 experiments, P. Perruchet and C. Pacteau (see record 1991-00329-001) argued that implicitly acquired knowledge of a synthetic grammar consists of little more than knowledge of pairwise associations between pairs of letters in the grammar. By comparing their results with a study by R. C. Mathews et al (see record 1990-03549-001), it is argued that (a) implicitly acquired knowledge is much richer and more abstract than suggested by Perruchet and Pacteau, (b) their recognition measures are less sensitive than the recall measures of Mathews et al for detecting conscious awareness of implicit knowledge, and (c) fragmentary knowledge of a grammar constitutes abstract rules that enable performance of complex tasks when integrated into a system for combining knowledge across rules. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of similarity in human associative learning.

In 2 experiments, humans received sequences of patterns that were similar (AX→BX, AY→BY, AZ→BZ) or dissimilar (CX→DY, CY→DZ, CZ→DX). The patterns were portrayed as bugs that could be eliminated with 2 insecticide sprays (red or blue). Either spray eliminated bugs with Features A and C, and participants learned by trial and error to use one spray (e.g., red) to eliminate bugs with Feature B and the other spray (e.g., blue) to eliminate those with Feature D. In Experiment 1, participants' spray choice for bugs with Feature A came to match that used to eliminate bugs with Feature B, but there was no such associative transfer between Features C and D. That is, similarity promoted associative transfer of responding between paired patterns when the features used to manipulate similarity (i.e., X, Y, and Z) were irrelevant. In Experiment 2, in which X, Y, and Z were relevant to the solution of configural discrimination, similarity hindered such associative transfer. These results complement those found in pigeons (R. A. Rescorla & D. J. Gillan, 1980) and indicate that similarity should not be accorded independent status as a principle of associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time delay and similarity effects in facial recognition.

Conducted 4 experiments to investigate the ability to 232 undergraduates to recognize a target person, whom they had previously seen in slides or a film, in a test series of pictures. Exp I, which manipulated time delay between seeing the target and starting the test series (from 4 min to 1 wk), demonstrated that delay had no effect on recognition performance. The other 3 studies manipulated similarity between the target person and the decoy pictures preceding the target in the search series. The greater the target-decoy similarity, the poorer the recognition performance. A significant Target Position * Similarity interaction indicated the presence of a larger performance decrement due to position when similarity level was high. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations among the anxiolytic effects of septal, hippocampal, and amygdaloid lesions.

Fear reactions of rats given bilateral lesions to the septum, hippocampus, or amygdala were compared with those of rats given sham lesions, in 2 animal models of anxiety: the shock-probe burying test and the elevated plus-maze test. Septal lesions produced anxiolytic effects in both tests (i.e., an increase in open-arm activity and a decrease in burying), whereas hippocampal and amygdaloid lesions produced neither of these effects. On the other hand, hippocampal and amygdaloid lesions impaired rats' passive avoidance of the electrified shock-probe, whereas septal lesions did not. These dissociations suggest that limbic structures such as the septum, amygdala, and hippocampus exert parallel but distinct control over different fear reactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)