Christiansen, M.H. and Chater, N. (1999) Connectionist natural language processing: The state of the art. Cognitive Science, 23, 417-437.

This Special Issue on Connectionist Models of Human Language Processing provides an opportunity for an appraisal both of specific connectionist models and of the status and utility of connectionist models of language in general. .........We argue that connectionist psycholinguistics has already had a significant impact on the psychology of language, and that connectionist models are likely to have an important influence on future research.

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Coleman, S. L., Brown, V. R., Levine, D. S., & Mellgren, R. L. (2005). A neural network model of foraging decisions made under predation risk. Cognitive Affective & Behavioral Neuroscience, 5(4), 434-451.

This article develops the cognitive-emotional forager (CEF) model, a novel application of a neural network to dynamical processes in foraging behavior. The CEF is based on a neural network known as the gated dipole, introduced by Grossberg, which is capable of representing short-term affective reactions in a manner similar to Solomon and Corbit's (1974) opponent process theory. The model incorporates a trade-off between approach toward food and avoidance of predation tinder varying levels of motivation induced by hunger. The results of simulations in a simple patch selection paradigm, using a lifetime fitness criterion for comparison, indicate that the CEF model is capable of nearly optimal foraging and outperforms a run-of-luck rule-of-thumb model. Models such as the one presented here can illuminate the underlying cognitive and motivational components of animal decision making.

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Colunga, E., & Smith, L. B. (2005). From the lexicon to expectations about kinds: A role for associative learning. Psychological Review, 112(2), 347-382.

In the novel noun generalization task, 2 1/2-year-old children display generalized expectations about how solid and nonsolid things are named, extending names for never-before-encountered solids by shape and for never-before-encountered nonsolids by material. This distinction between solids and nonsolids has been interpreted in terms of an ontological distinction between objects and substances. Nine simulations and behavioral experiments tested the hypothesis that these expectations arise from the correlations characterizing early learned noun categories. In the simulation studies, connectionist networks were trained on noun vocabularies modeled after those of children. These networks formed generalized expectations about solids and nonsolids that match children's performances in the novel noun generalization task in the very different languages of English and Japanese. The simulations also generate new predictions supported by new experiments with children. Implications are discussed in terms of children's development of distinctions between kinds of categories and in terms of the nature of this knowledge.

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Joanisse, M. F., & Seidenberg, M. S. (2005). Imaging the past: Neural activation in frontal and temporal regions during regular and irregular past-tense processing. Cognitive Affective & Behavioral Neuroscience, 5(3), 282-296.

This article presents fMRI evidence bearing on dual-mechanism versus connectionist theories of inflectional morphology. Ten participants were scanned at 4 Tesla as they covertly generated the past tenses of real and nonce (nonword) verbs presented auditorily. Regular past tenses (e.g., walked, wagged) and irregular past tenses (e.g., took, slept) produced similar patterns of activation in the posterior temporal lobe in both hemispheres. In contrast, there was greater activation in left and right inferior frontal gyrus for regular past tenses than for irregular past tenses. Similar previous results have been taken as evidence for the dual-mechanism theory of the past tense (Pinker & Ullman, 2002). However, additional analyses indicated that irregulars that were phonologically similar to regulars (e.g., slept, fled, sold) produced the same level of activation as did regulars, and significantly more activation than did irregulars that were not phonologically similar to regulars (e.g., took, gave). Thus, activation patterns were predicted by phonological characteristics of the past tense rather than by the rule-governed versus exception distinction that is central to the dual-mechanism framework. The results are consistent with a constraint satisfaction model in which phonological, semantic, and other probabilistic constraints jointly determine the past tense, with different degrees of involvement for different verbs.

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Joanisse, M.F. and Seidenberg, M.S. (1999) Impairments in verb morphology after brain injury: A connectionist model. Proceedings of the National Academy of Sciences of the United States of America, 96, 7592-7597.

The formation of the past tense of verbs in English has been the focus of the debate concerning connectionist vs. symbolic accounts of language. Brain-injured patients differ with respect to whether they are more impaired in generating irregular past tenses (TAKE-TOOK) or past tenses for nonce verbs (WUG-WUGGED). Such dissociations have been taken as evidence for distinct "rule" and "associative" memory systems in morphology and against the connectionist approach in which a single system is used for all forms. We describe a simulation model in which these impairments arise from damage to phonological or semantic information, which have different effects on generalization and irregular forms, respectively. The results provide an account of the bases of impairments in verb morphology and show that these impairments can be explained within connectionist models that do not use rules or a separate mechanism for exceptions.

Maia, T. V., & Cleeremans, A. (2005). Consciousness: converging insights from connectionist modeling and neuroscience. Trends in Cognitive Sciences, 9(8), 397-404.

Over the past decade, many findings in cognitive neuroscience have resulted in the view that selective attention, working memory and cognitive control involve competition between widely distributed representations. This competition is biased by top-down projections (notably from prefrontal cortex), which can selectively enhance some representations over others. This view has now been implemented in several connectionist models. In this review, we emphasize the relevance of these models to understanding consciousness. Interestingly, the models we review have striking similarities to others directly aimed at implementing 'global workspace theory'. All of these models embody a fundamental principle that has been used in many connectionist models over the past twenty years: global constraint satisfaction.

Mareschal, D., & Johnson, S. P. (2002). Learning to perceive object unity: a connectionist account. Developmental Science, 5(2), 151-172.

To explore questions of how human infants begin to perceive partly occluded objects, we devised two connectionist models of perceptual development. The models were endowed with an existing ability to detect several kinds of visual information that have been found important in infants' and adults' perception of object unity (motion, co-motion, common motion, relatability, parallelism, texture and T-junctions). They were then presented with stimuli consisting of either one or two objects and an occluding screen. The models' task was to determine whether the objector objects were joined when such a percept was ambiguous, after specified amounts of training with events in which a subset of possible visual information was provided. The model that was trained in an enriched environment achieved superior levels of performance and was able to generalize veridical percepts to a wide range of novel stimuli. Implications for perceptual development in humans, current theories of development and origins of knowledge are discussed.

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Plunkett, K. and Juola, P. (1999) A connectionist model of English past tense and plural morphology. Cognitive Science, 23, 463-490.

The acquisition of English noun and verb morphology is modeled using a single-system connectionist network. The network is trained to produce the plurals and past tense forms of a large corpus of monosyllabic English nouns and verbs. The developmental trajectory of network performance is analyzed in detail and is shown to mimic a number of important features of the acquisition of English noun and verb morphology in young children. These include an initial error-free period of performance on both nouns and verbs followed by a period of intermittent over-regularization of irregular nouns and verbs. Errors in the model show evidence of phonological conditioning and frequency effects. Furthermore, the network demonstrates a strong tendency to regularize denominal verbs and deverbal nouns and masters the principles of voicing assimilation. Despite their incorporation into a single-system network, nouns and verbs exhibit some important differences in their profiles of acquisition. Most importantly, noun inflections are acquired earlier than verb inflections. The simulations generate several empirical predictions that can be used to evaluate further the suitability of this type of cognitive architecture in the domain of inflectional morphology.

Queller, S., & Smith, E. R. (2002). Subtyping versus bookkeeping in stereotype learning and change: Connectionist simulations and empirical findings. Journal of Personality and Social Psychology, 82(3), 300-313.

A distributed connectionist network can account for both bookkeeping (M. Rothbatt. 1981) and subtyping (NI, B. Brewer, V. Dull, & L. Lui, 19 1 S. E. Taylor, 1981) effects. The finding traditionally regarded as demonstrating subtyping is that exposure to moderate (compared with extreme) disconfirmers leads to subsequent ratings of the group that are less stereotypic. Despite learning that is incremental and analogous to bookkeeping, the simulations replicate this finding and suggest that the "subtyping" pattern of, results will be drastically reduced if disconfirmers are encountered before the stereotype is well-established. This novel prediction holds with human participants and offers, a tantalizing suggestion: Although moderate disconfirmers may produce more stereotype change, stereotype development might be discouraged by exposure to either extreme or moderate disconfirmers.