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J L McClelland

Publications and source records attributed to J L McClelland.

15 recordsLinked to original sources
PubMed1992

A parallel distributed processing approach to automaticity.

We consider how a particular set of information processing principles, developed within the parallel distributed processing (PDP) framework, can address issues concerning automaticity. These principles include graded, activation-based processing that is subject to attentional modulation; incremental, connection-based learning; and interactivity and competition in processing. We show how simulation models, based on these principles, can account for the major phenomena associated with automaticity, as well as many of those that have been troublesome for more traditional theories. In particular, we show how the PDP framework provides an alternative to the usual dichotomy between automatic and controlled processing and can explain the relative nature of automaticity as well as the fact that seemingly automatic processes can be influenced by attention. We also discuss how this framework can provide insight into the role that bidirectional influences play in processing: that is, how attention can influence processing at the same time that processing influences attention. Simulation models of the Stroop color-word task and the Eriksen response-competition task are described that help illustrate the application of the principles to performance in specific behavioral tasks.

Association Learning↗
PubMed1991

Stochastic interactive processes and the effect of context on perception.

The effects of context on perceptual identification responses given without time pressure are well-described by classical models in which contextual and stimulus information exert independent effects. A recent article by Massaro (1989) raises the possibility that interactive models, such as the TRACE model of speech perception, are inherently incompatible with these classical context effects. The present article shows that this incompatibility hypothesis can be rejected. Mathematical analysis and computer simulation methods are used to show that interactive models can exhibit the classical effects of context, if there is variability in the input to the network or if there is intrinsic variability in the network itself. A variety of interactive models which incorporate variability can all produce the classical context effects, at least under some conditions; the conditions are rather general in the case of one of the variants. The findings suggest that interactive models should not be viewed as alternatives to classical accounts, but as hypotheses about the dynamics of information processing that lead to the global asymptotic behavior that the classical models describe.

Attention↗
PubMed1991

Learning the structure of event sequences.

How is complex sequential material acquired, processed, and represented when there is no intention to learn? Two experiments exploring a choice reaction time task are reported. Unknown to Ss, successive stimuli followed a sequence derived from a "noisy" finite-state grammar. After considerable practice (60,000 exposures) with Experiment 1, Ss acquired a complex body of procedural knowledge about the sequential structure of the material. Experiment 2 was an attempt to identify limits on Ss ability to encode the temporal context by using more distant contingencies that spanned irrelevant material. Taken together, the results indicate that Ss become increasingly sensitive to the temporal context set by previous elements of the sequence, up to 3 elements. Responses are also affected by priming effects from recent trials. A connectionist model that incorporates sensitivity to the sequential structure and to priming effects is shown to capture key aspects of both acquisition and processing and to account for the interaction between attention and sequence structure reported by Cohen, Ivry, and Keele (1990).

Adolescent↗
PubMed1991

A computational model of semantic memory impairment: modality specificity and emergent category specificity.

It is demonstrated how a modality-specific semantic memory system can account for category-specific impairments after brain damage. In Experiment 1, the hypothesis that visual and functional knowledge play different roles in the representation of living things and nonliving things is tested and confirmed. A parallel distributed processing model of semantic memory in which knowledge is subdivided by modality into visual and functional components is described. In Experiment 2, the model is lesioned, and it is confirmed that damage to visual semantics primarily impairs knowledge of living things, and damage to functional semantics primarily impairs knowledge of nonliving things. In Experiment 3, it is demonstrated that the model accounts naturally for a finding that had appeared problematic for a modality-specific architecture, namely, impaired retrieval of functional knowledge about living things. Finally, in Experiment 4, it is shown how the model can account for a recent observation of impaired knowledge of living things only when knowledge is probed verbally.

Amnesia↗
PubMed1990

On the control of automatic processes: a parallel distributed processing account of the Stroop effect.

Traditional views of automaticity are in need of revision. For example, automaticity often has been treated as an all-or-none phenomenon, and traditional theories have held that automatic processes are independent of attention. Yet recent empirical data suggest that automatic processes are continuous, and furthermore are subject to attentional control. A model of attention is presented to address these issues. Within a parallel distributed processing framework, it is proposed that the attributes of automaticity depend on the strength of a processing pathway and that strength increases with training. With the Stroop effect as an example, automatic processes are shown to be continuous and to emerge gradually with practice. Specifically, a computational model of the Stroop task simulates the time course of processing as well as the effects of learning. This was accomplished by combining the cascade mechanism described by McClelland (1979) with the backpropagation learning algorithm (Rumelhart, Hinton, & Williams, 1986). The model can simulate performance in the standard Stroop task, as well as aspects of performance in variants of this task that manipulate stimulus-onset asynchrony, response set, and degree of practice. The model presented is contrasted against other models, and its relation to many of the central issues in the literature on attention, automaticity, and interference is discussed.

Attention↗
PubMed1989

Conjunctive search for one and two identical targets.

The assumptions of feature integration theory as a blind, serial, self-terminating search (SSTS) mechanism are extended to displays containing 2 identical targets. The SSTS predicts no differences in negative-response displays, which require an exhaustive search of the display. Quantitative predictions are confirmed for the positive responses, but not for the negatives, suggesting that the SSTS model is incorrect. Two possible explanations for the results in the negative conditions, differential search rates and early quitting in the negatives, are rejected. It is suggested that using any self-terminating search mechanism will lead to difficulty in interpreting the results, including accounts for which the search is parallel over small groups of items. A resource-limited parallel model, which is based on the diffusion model of Ratcliff (1978), appears to fit the data well.

Adult↗
PubMed1989

A distributed, developmental model of word recognition and naming.

A parallel distributed processing model of visual word recognition and pronunciation is described. The model consists of sets of orthographic and phonological units and an interlevel of hidden units. Weights on connections between units were modified during a training phase using the back-propagation learning algorithm. The model simulates many aspects of human performance, including (a) differences between words in terms of processing difficulty, (b) pronunciation of novel items, (c) differences between readers in terms of word recognition skill, (d) transitions from beginning to skilled reading, and (e) differences in performance on lexical decision and naming tasks. The model's behavior early in the learning phase corresponds to that of children acquiring word recognition skills. Training with a smaller number of hidden units produces output characteristic of many dyslexic readers. Naming is simulated without pronunciation rules, and lexical decisions are simulated without accessing word-level representations. The performance of the model is largely determined by three factors: the nature of the input, a significant fragment of written English; the learning rule, which encodes the implicit structure of the orthography in the weights on connections; and the architecture of the system, which influences the scope of what can be learned.

Dyslexia↗
PubMed1986

Perceptual interactions in two-word displays: familiarity and similarity effects.

Previous studies have demonstrated the existence of perceptual interactions in the processing of two-word displays such as SAND LANE. When postcued to report one of the two words, subjects often make migration errors, in that the report of the specified word includes a letter of the other word (e.g., LAND or SANE instead of SAND). We find that migrations depend on the abstract, structural similarity of the strings, but not on the physical similarity; on whether the strings are words; and on whether the possible migration responses are words. We also rule out an interpretation of migration errors that attributes them to a guessing strategy. Our findings are interpreted in terms of models in which both strings simultaneously access high-level structural knowledge, that is, knowledge about what sequences of letters fit together to form familiar wholes.

Adult↗
PubMed1985

Distributed memory and the representation of general and specific information.

We describe a distributed model of information processing and memory and apply it to the representation of general and specific information. The model consists of a large number of simple processing elements which send excitatory and inhibitory signals to each other via modifiable connections. Information processing is thought of as the process whereby patterns of activation are formed over the units in the model through their excitatory and inhibitory interactions. The memory trace of a processing event is the change or increment to the strengths of the interconnections that results from the processing event. The traces of separate events are superimposed on each other in the values of the connection strengths that result from the entire set of traces stored in the memory. The model is applied to a number of findings related to the question of whether we store abstract representations or an enumeration of specific experiences in memory. The model simulates the results of a number of important experiments which have been taken as evidence for the enumeration of specific experiences. At the same time, it shows how the functional equivalent of abstract representations--prototypes, logogens, and even rules--can emerge from the superposition of traces of specific experiences, when the conditions are right for this to happen. In essence, the model captures the structure present in a set of input patterns; thus, it behaves as though it had learned prototypes or rules, to the extent that the structure of the environment it has learned about can be captured by describing it in terms of these abstractions.

Association Learning↗
PubMed1980

Context and the allocation of resources in word recognition.

Three experiments are reported that investigate the effects of context on the use of limited processing resources in word recognition. On each trial in all of the experiments, the subjects were presented with an incomplete sentence followed by a target display containing a word and two digits. In all cases, accuracy at reporting the word was affected by context, as expected. The effect of context on processing resources was examined by considering the accuracy of reports of the digits in cases in which the word did or did not fit the context. Accuracy of digit report was greater for digits surrounding words in related context, but only when the subjects were required to report the word before reporting the digits. There was no effect of word context on the digit report when subjects had to report the digits first. There was likewise no effect on accuracy of digit report when subjects were required to report only the word or only the digits, even when the cue was presented 250 msec after the target display was replaced by a patterned mask. The results suggest that the effect of context on the resources consumed in word recognition is restricted to aspects of processing that can be delayed until the subject is required to select an overt response, and a simple interpretation of the results may be given in terms of a slight modification of Morton's model of the interaction of stimulus information and context.

Attention↗
PubMed1978

Perception and masking of wholes and parts.

These exerpiments show that the effects of masking on reports of target lines depend on the context in which the target lines appear. Subjects viewed brief presentations of target lines either alone or in drawings of three-dimensional objects, and each target display was preceded and followed by one of several different mask stimuli. There were two main findings: (a) A mask containing a haphazard array of lines interfered more with single lines than it did with lines in objects. (b) A mask containing drawings of the object displays interfered more with lines in objects than did either of two control masks containing relatively flat, less coherent patterns. In a control condition, the object mask interfered slightly less with reports of single lines than either of the control masks did. The discussion considers how the effects obtained here bear on models of the processing of wholistic stimuli and their component parts.

Discrimination, Psychological↗
PubMed1976

Preliminary letter identification in the perception of words and nonwords.

Words with mixed uppercase and lowercase letters (e.g. fAdE) were perceived more accurately than mixed-case pseudowords (e.g. gAdE), and mixed-case pseudowords were perceived more accurately than mixed-case unrelated letter strings (e.g. eFdT). In addition, same-case words were perceived more accurately than their mixed-case counterparts. The same held true for pseudowords but not for unrelated letter strings. The results are compatible with the view that both letter identify and visual form information are used in word perception.

Awareness↗