We show that a popular class of connectionist models (which we label 'first order connectionism') looks unlikely to provide the kind of resources required by the hypothesis. We examine some alternative hybrid models that seem more promising. Finally, we raise a more purely philosophical issue concerning the conditions under which a being can count as a genuine believer or cognizer.".

The vast expressive power of language is made possible by two principles: the arbitrary soundmeaning pairing underlying words, and the discrete combinatorial system underlying grammar. These principles implicate distinct cognitive mechanisms: associative memory and symbolmanipulating rules. The distinction may be seen in the difference between regular inflection (e.g., walk-walked), which is productive and open-ended and hence implicates a rule, and irregular inflection (e.g., come-came, which is idiosyncratic and closed and hence implicates individually memorized words. Nonetheless, two very different theories have (...) attempted to collapse the distinction; generative phonology invokes minor rules to generate irregular as well as regular forms, and connectionism invokes a pattern associator memory to store and retrieve regular as well as irregular forms. I present evidence from three disciplines that supports the traditional word/rule distinction, though with an enriched conception of lexical memory with some of the properties of a pattern-associator. Rules, nonetheless, are distinct from patternassociation, because a rule concatenates a suffix to a symbol for verbs, so it does not require access to memorized verbs or their sound patterns, but applies as the "default," whenever memory access fails. I present a dozen such circumstances, including novel, unusual-sounding, and rootless and headless derived words, in which people inflect the words regularly (explaining quirks like flied out, low-lifes, and Walkmans). A comparison of English to other languages shows that contrary to the connectionist account, default suffixation is not due to numerous regular words reinforcing a pattern in associative memory, but to a memory-independent, symbol-concatenating mental operation. (shrink)

Connectionist models provide a promising alternative to the traditional computational approach that has for several decades dominated cognitive science and artificial intelligence, although the nature of connectionist models and their relation to symbol processing remains controversial. Connectionist models can be characterized by three general computational features: distinct layers of interconnected units, recursive rules for updating the strengths of the connections during learning, and “simple” homogeneous computing elements. Using just these three features one can construct surprisingly elegant and powerful models of (...) memory, perception, motor control, categorization, and reasoning. What makes the connectionist approach unique is not its variety of representational possibilities or its departure from explicit rule-based models, or even its preoccupation with the brain metaphor. Rather, it is that connectionist models can be used to explore systematically the complex interaction between learning and representation, as we try to demonstrate through the analysis of several large networks. (shrink)

Supporters of eliminative connectionism have argued for a pattern association-based explanation of language learning and language processing. They deny that explicit rules and symbolic representations play any role in language processing and cognition in general. Their argument is based to a large extent on two artificial neural network (ANN) models that are claimed to be able to learn the past tenses of English verbs (Rumelhart & McClelland, 1986, Parallel distributed processing, Vol. 2, Cambridge, MA: MIT Press; MacWhinney & Leinbach, 1991, (...) Cognition, 40, 121-157). In this article we critically review Rumelhart and McClelland's as well as MacWhinney and Leinbach's ANN models and conclude that they do not succeed in the assigned task of learning the past tenses of English verbs. In order to answer their challenge to the symbolic processing approach, we present our symbolic pattern associator (SPA)-a general-purpose pattern associator that can learn to associate arbitrary discrete patterns. We carried out several experiments with the SPA using the same set of verbs that was used in MacWhinney and Leinbach's simulation with more realistic training and testing procedures. The SPA outperformed the connectionist models by a wide margin in the accuracy of learning, and successful inductive generalizations to unseen verbs. Our SPA has very natural and psychologically realistic explanations to many psychological effects such as U-shaped learning curve, and is much closer to human subjects in predicting past tense of the pseudo-verbs. In contrast to ANNs, whose internal representations are entirely opaque, the SPA can represent the acquired knowledge in the form of production rules that allow for further higher-level processing and integration, resulting in linguistically realistic associative templates for irregular verbs and production rules for regular verbs. In the light of these findings, we conclude that eliminative connectionists' vision of cognition as simple pattern association and pattern recognition without symbolic representation is inadequate. Pattern association as such does not imply rule-less or cue-based models of language acquisition or of human learning in general. (shrink)

Following much work in linguistic theory, it is hypothesized that the language faculty has a modular structure and consists of two basic components, a lexicon of (structured) entries and a computational system of combinatorial operations to form larger linguistic expressions from lexical entries. This target article provides evidence for the dual nature of the language faculty by describing recent results of a multidisciplinary investigation of German inflection. We have examined: (1) its linguistic representation, focussing on noun plurals and verb inflection (...) (participles), (2) processes involved in the way adults produce and comprehend inflected words, (3) brain potentials generated during the processing of inflected words, and (4) the way children acquire and use inflection. It will be shown that the evidence from all these sources converges and supports the distinction between lexical entries and combinatorial operations. (shrink)

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. (shrink)

Language comes so naturally to us that we are apt to forget what a strange and miraculous gift it is. Over the next hour you will sit in your chairs listening to a man make noise as he exhales. Why would you do such a thing? Not because the sounds are particularly melodious, but because the sounds convey information in the exact sequence of hisses and hums and squeaks and pops. As you recover the information, you think the thoughts that (...) I want you to think. Right now I am conveying ideas about language itself, but with a slightly different sequence of hisses and pops I could be talking about anything from theories of the origin of the universe to the latest plot twists in your favorite daytime drama. The fundamental scientific problem raised by language is to explain this vast expressive power. What is the trick behind our ability to fill each other’s heads with so many kinds of thoughts? (shrink)

Clahsen's characterization of nondefault inflection as based exclusively on lexical entries does not capture the full range of empirical data on German inflection. In the verb system differential effects of lexical frequency seem to be input-related rather than affecting morphological production. In the noun system, the generalization properties of -n and -e plurals exceed mere analogy-based productivity.

We report an experiment that unambiguously shows an effect of full-form frequency for fully regular Dutch inflected verbs falling into Clahsen's “default” category, negating Clahsen's claim that regular complex words in the default category are not stored.

Results from our laboratories show clear frequency effects for regularly inflected forms in both German and English. Moreover, there does not seem to be sufficient evidence to treat the -s plural as the default plural in German. Together, these data do not support a dual modular structure of the language faculty.

This commentary concentrates on the nature of irregularity in morphology. What is called “irregular” in the target article by Clahsen is not a homogeneous class. Rather, there are areas of strong subregularities in the domains both of German participle formation and of German plural information that need to be distinguished from the irregular domain.

German noun plurals not ending in -s are not as irregular as Clahsen suggests. Feminine nouns get the -n plural, unless they umlaut and are subject to a constraint that requires a reduced final syllable in the plural. Another regular class is masculine nouns ending in schwa, which are weakly inflected. It is suggested that more differentiated psycholinguistic experiments can identify these regularities.

This book is the first to survey current developments in computational phonology, and it does so in a way that is accessible to computational linguists, phonologists and computer scientists alike.