Combining exemplar-based category representations and connectionist learning rules.

Adaptive network and exemplar-similarity models were compared on their ability to predict category learning and transfer data. An exemplar-based network (J. K. Kruschke, 1990, 1992) that combines key aspects of both modeling approaches was also tested. The exemplar-based network incorporates an exemplar-based category representation in which exemplars become associated to categories through the same error-driven, interactive learning rules that are assumed in standard adaptive networks. Exp 1, which partially replicated and extended the probabilistic classification learning paradigm of M. A. Gluck and G. H. Bower (1988), demonstrated the importance of an error-driven learning rule. Exp 2, which extended the classification learning paradigm of D. L. Medin and M. M. Schaffer (1978) that discriminated between exemplar and prototype models, demonstrated the importance of an exemplar-based category representation. Only the exemplar-based network accounted for all the major qualitative phenomena; it also achieved good quantitative predictions of the learning and transfer data in both experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ALCOVE: An exemplar-based connectionist model of category learning.

ALCOVE (attention learning covering map) is a connectionist model of category learning that incorporates an exemplar-based representation (D. L. Medin and M. M. Schaffer, 1978; R. M. Nosofsky, 1986) with error-driven learning (M. A. Gluck and G. H. Bower, 1988; D. E. Rumelhart et al, 1986). ALCOVE selectively attends to relevant stimulus dimensions, is sensitive to correlated dimensions, can account for a form of base-rate neglect, does not suffer catastrophic forgetting, and can exhibit 3-stage (U-shaped) learning of high-frequency exceptions to rules, whereas such effects are not easily accounted for by models using other combinations of representation and learning method. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ubiquitous nature of the Hebb repetition effect: Error learning mistaken for the absence of sequence learning.

Sequence learning is essential in cognition and underpins activities such as language and skill acquisition. One classical demonstration of sequence learning is that of the Hebb repetition effect, whereby serial recall improves over repetitions on a repeated list relative to random lists. When addressing the question of which mechanism underlies the effect, the traditional approach is to prevent the action of processes thought to be responsible for sequence learning: If the typical Hebb repetition effect is reduced, these processes are key to the effect, researchers claim. By reanalyzing the data of F. B. R. Parmentier, M. T. Maybery, M. Huitson, and D. M. Jones (2008)—who reported no Hebb effect for sequences of auditory–spatial stimuli—we revealed that error learning can be mistaken for the absence of sequence learning. Indeed, incorrect responses are reproduced increasingly over repetitions. Our findings suggest that the Hebb repetition effect can be associated with response learning as well as stimulus processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence of anticipatory eye movements in the spatial Hebb repetition effect: Insights for modeling sequence learning.

In the present study, the authors offer a window onto the mechanisms that drive the Hebb repetition effect through the analysis of eye movement and recall performance. In a spatial serial recall task in which sequences of dots are to be remembered in order, when one particular series is repeated every 4 trials, memory performance markedly improves over repetitions. This is known as the Hebb repetition effect. Eye movement recorded during the presentation of the to-be-remembered (TBR) information revealed that for the repeated sequence, participants fixated the location of the next TBR location before the actual presentation of the dot. The extent to which a TBR location was anticipated increased over repetition and occurred only for post-initial positions of the repeated sequence. Eye movement–based rehearsal activity was related to recall performance but not to sequence learning. The findings provide further evidence of anticipatory behavior in sequence learning and place key constraints on modeling the Hebb repetition effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Order or disorder? Impaired Hebb learning in dyslexia.

The present study offers an integrative account proposing that dyslexia and its various associated cognitive impairments reflect an underlying deficit in the long-term learning of serial-order information, here operationalized as Hebb repetition learning. In nondyslexic individuals, improved immediate serial recall is typically observed when one particular sequence of items is repeated across an experimental session, a phenomenon known as the Hebb repetition effect. Starting from the critical observation that individuals with dyslexia seem to be selectively impaired in cognitive tasks that involve processing of serial order, the present study is the first to test and confirm the hypothesis that the Hebb repetition effect is affected in dyslexia, even for nonverbal modalities. We present a theoretical framework in which the Hebb repetition effect is assumed to be a laboratory analogue of naturalistic word learning, on the basis of which we argue that dyslexia is characterized by an impairment of serial-order learning that affects language learning and processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Learning correct responses and errors in the Hebb repetition effect: Two faces of the same coin.

In a serial recall task, the Hebb repetition effect occurs when recall performance improves for a sequence repeated throughout the experimental session. This phenomenon has been replicated many times. Nevertheless, such cumulative learning seldom leads to perfect recall of the whole sequence, and errors persist. Here the authors report evidence that there is another side to the Hebb repetition effect that involves learning errors produced in a repeated sequence. A learning measure based on past recalls (correct or incorrect) shows that the probability of a given response increases with the number of prior occurrences of that response. The pattern of results reveals another manifestation of the Hebb repetition effect and speaks to the nature of implicit learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Instantiated features and the use of "rules."

Classification "rules" in expert and everyday discourse are usually deficient by formal standards, lacking explicit decision procedures and precise terms. The authors argue that a central function of such weak rules is to focus on perceptual learning rather than to provide definitions. In 5 experiments, transfer following learning of family resemblance categories was influenced more by familiar-appearing features than by novel-appearing features equally acceptable under the rule. This occurred both when rules were induced and when rules were given at the beginning of instruction. To model this and other phenomena in categorization, features must be represented on 2 levels: informational and instantiated. These 2 feature levels are crucial to provide broad generalization while reflecting the known peculiarities of a complex world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blocking in category learning.

Many theories of category learning assume that learning is driven by a need to minimize classification error. When there is no classification error, therefore, learning of individual features should be negligible. The authors tested this hypothesis by conducting three category-learning experiments adapted from an associative learning blocking paradigm. Contrary to an error-driven account of learning, participants learned a wide range of information when they learned about categories, and blocking effects were difficult to obtain. Conversely, when participants learned to predict an outcome in a task with the same formal structure and materials, blocking effects were robust and followed the predictions of error-driven learning. The authors discuss their findings in relation to models of category learning and the usefulness of category knowledge in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychological investigations of cognitive deficit in elderly psychiatric patients.

"An attempt has been made to review the experimental literature to date on intellectual and learning impairment in elderly psychiatric patients. Certain consistent relationships emerge from these studies indicative of possible links between learning ability and that differential cognitive impairment which is to be found in at least the early stages of senile deterioration. The neuropsychological theory propounded by Hebb seems to provide a convenient conceptual framework for the relations so far established." 83-item bibliography. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Hebbian perspective on mind-brain relations.

Reviews the book, Essay on Mind by D.O. Hebb (1980). This is the third book by Canada's most distinguished and influential psychologist, Donald Olding Hebb. Essay on Mind presents readers with an opportunity to see why Hebb and his writings have had such an impact: In this book, Hebb presents a succinct account of the development of cell-assembly theory and its applications, as well as views on important philosophical and scientific issues. Hebb argues that his type of theory is not "mere translation" because the physiological theory and data impose constraints on psychological concepts. Moreover, such theorizing can be useful in that it leads to new evidence or tells a theorist how to look at available evidence from different aspects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Donald Olding Hebb: 1904-1985.

Presents an obituary for Donald Olding Hebb, who died on August 20, 1985 and was considered by some to be the most influential psychologist of the century. Hebb gained prominence, nationally and internationally, with the publication of The Organization of Behavior (1949). Because of the novel and innovative nature of the neuropsychological theory presented in this landmark publication, Hebb's influence on psychology was immediate and substantial. It led to a major re-assessment of prevailing views about the basic subjects of learning, intelligence, memory, perception, motivation and emotion. Hebb was not only one of the most influential psychologists in this century but also one of the most honored and recognized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition learning in the immediate serial recall of visual and auditory materials.

In 5 experiments, a Hebb repetition effect, that is, improved immediate serial recall of an (unannounced) repeating list, was demonstrated in the immediate serial recall of visual materials, even when use of phonological short-term memory was blocked by concurrent articulation. The learning of a repeatedly presented letter list in one modality (auditory or visual) did not transfer to give improved performance on the same list in the other modality. This result was not replicated for word lists, however, for which asymmetric transfer was observed. Inferences are made about the structure of short-term memory and about the nature of the Hebb repetition effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition priming of words, pseudowords, and nonwords.

In 5 experiments, the authors assessed repetition priming for words, pseudowords, and nonwords using a task that combines an implicit perceptual fluency measure and a recognition memory assessment for each list item. Words and pseudowords generated a consistently strong repetition effect even when there was a failure to recognize the stimulus. In 2 of the experiments, the repetition effect for nonwords was reliably above chance even when there was a failure to recognize the stimulus. The authors propose a parallel distributed processing (PDP) model based on the work of J. McClelland and D. Rumelhart (1985) as a way to understand the mechanisms potentially responsible for the pattern of findings. Although the error-driven nature of learning in the model results in a poor fit to the nonword priming data, this is not endemic to all PDP models. Using a model based on Hebbian learning, the authors instantiate a property that they believe is characteristic of implicit memory-that learning is primarily based on the strengthening of connections between units that become active during the processing of a stimulus. This model provides a far more satisfactory account of the data than does the error-driven model. (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)     

Category dimensionality and feature knowledge: When more features are learned as easily as fewer.

Three experiments compared the learning of lower-dimensional family resemblance categories (4 dimensions) with the learning of higher-dimensional ones (8 dimensions). Category-learning models incorporating error-driven learning, hypothesis testing, or limited capacity attention predict that additional dimensions should either increase learning difficulty or decrease learning of individual features. Contrary to these predictions, the experiments showed no slower learning of high-dimensional categories; instead, subjects learned more features from high-dimensional categories than from low-dimensional categories. This result obtained both in standard learning with feedback and in noncontingent, observational learning. These results show that rather than interfering with learning, categories with more dimensions cause individuals to learn more. The authors contrast the learning of family resemblance categories with learning in classical conditioning and probability learning paradigms, in which competition among features is well documented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coherence of gamma-band EEG activity as a basis for associative learning

Different regions of the brain must communicate with each other to provide the basis for the integration of sensory information, sensory-motor coordination and many other functions that are critical for learning, memory, information processing, perception and the behaviour of organisms. Hebb suggested that this is accomplished by the formation of assemblies of cells whose synaptic linkages are strengthened whenever the cells are activated or 'ignited' synchronously. Hebb's seminal concept has intrigued investigators since its formulation, but the technology to demonstrate its existence had been lacking until the past decade. Previous studies have shown that very fast electroencephalographic activity in the gamma band (20-70 Hz) increases during, and may be involved in, the formation of percepts and memory, linguistic processing, and other behavioural and perceptual functions. We show here that increased gamma-band activity is also involved in associative learning. In addition, we find that another measure, gamma-band coherence, increases between regions of the brain that receive the two classes of stimuli involved in an associative-learning procedure in humans. An increase in coherence could fulfil the criteria required for the formation of hebbian cell assemblies, binding together parts of the brain that must communicate with one another in order for associative learning to take place. In this way, coherence may be a signature for this and other types of learning.     

Memory for serial order: A network model of the phonological loop and its timing.

A connectionist model of human short-term memory is presented that extends the "phonological loop" (A. D. Baddeley, see record 1986-98526-000) to encompass serial order and learning. Psychological and neuropsychological data motivate separate layers of lexical, timing, and input and output phonemic information. Connection weights between layers show Hebbian learning and decay over short and long time scales. At recall, the timing signal is rerun, phonemic information feeds back from output to input, and lexical nodes compete to be selected. The selected node then receives decaying inhibition. The model provides an explanatory mechanism for the phonological loop and for the effects of serial position, presentation modality, lexicality, grouping, and Hebb repetition. It makes new psychological and neuropsychological predictions and is a starting point for understanding the role of the phonological loop in vocabulary acquisition and for interpreting data from functional neuroimaging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

APA Symposium: Control of Behavior through Motivation and Reward--Introductory Remarks.

Presents the opening remarks at a symposium held at the 1957 Annual Convention of the American Psychological Association. The focus of this symposium was on new developments in learning and major systematic approaches to learning. Three speakers were asked to provided their firsthand knowledge of this topic: Fred Skinner, Neal Miller, and Don Hebb. In addition to their technical qualifications, these men are all noted for their willingness to come out of the ivory tower and for their ability to present good talks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left to Right, Upside Down.

Comments on the D. O. Hebb article (see record 1964-01548-001), which considers theories concerned with the analysis of the complexity of the "central process" in thought and perception. The present author notes that reading of type by the printer who sets type by hand is quite different from the way Hebb describes. The printer always reads print from left to right, with the characters (letters) upside down. At the beginning of his apprenticeship, he is specifically instructed that he must never under any circumstances allow himself to read in the right-to-left, right-side-up manner that Hebb describes him as reading it. The author also argues that Hebb's error with regard to the question of how printers perceive type is not unrelated to his Jungian-like concept that the self-image is of only two parts, rather than of three parts as in the Freudian tradition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Effect of Old Age on the Learning of Supraspan Sequences.

Two experiments examined age-related differences in sequence learning using computerized versions of the D. O. Hebb (1961) paradigm. In this learning task, the participant executes immediate serial recall of 24 supraspan sequences. Without the participants' knowledge, 1 sequence is presented several times. Repetition leads to improved recall of this repeated sequence relative to random sequences. Results showed a dissociation in age-related learning deficits depending on the nature of the to-be-remembered material. The effect of repetition is similar for younger and older adults with familiar and unfamiliar verbal material (words and pseudowords) but is significantly reduced in older adults when learning is assessed with a visuospatial version of Hebb's supraspan learning task (P. M. Corsi, 1972). (PsycINFO Database Record (c) 2010 APA, all rights reserved)