ABSTRACT: In this article, we discuss the complex problem ofrelating genotype to phenotype and challenge the simple mapping ofgenes to higher level cognitive modules. We examine various methods that have been used to investigate this relation including quantitative genetics, molecular genetics, animal models, and in-depth psychological and computational studies ofdevelopmental disorders. Both single gene and multiple gene disorders indicate that the relationship between genotype and phenotype is very indirect and that, rather than identifying mere snapshots of developmental

In this chapter, we review computer models of cognition that have focused on the use of neural networks. These architectures were inspired by research into how computation works in the brain and subsequent work has produced models of cognition with a distinctive flavor. Processing is characterized by patterns of

The study of human intelligence was once dominated by symbolic approaches, but over the last 30 years an alternative approach has arisen. Symbols and processes that operate on them are often seen today as approximate characterizations of the emergent consequences of sub- or nonsymbolic processes, and a wide range of constructs in cognitive science can be understood as emergents. These include representational constructs (units, structures, rules), architectural constructs (central executive, declarative memory), and developmental processes and outcomes (stages, sensitive periods, neurocognitive modules, developmental disorders). The greatest achievements of human cognition may be largely emergent phenomena. It remains a challenge for the future to learn more about how these greatest achievements arise and to emulate them in artificial systems.

developmental disorders

For the last thirty years, cognitive scientists have attempted to describe the cognitive architecture of typically developing human beings, using, among other sources of evidence, the dissociations that result from developmental psychopathologies such as autism spectrum disorders, Williams syndrome, and Down syndrome. Thus, in his recent defense of the massive modularity hypothesis, Steven Pinker insists on the importance of such dissociations to identify the components of the typical cognitive architecture (2005, 4; my emphasis): This kind of faculty psychology has numerous advantages (...). It is supported by the existence of neurological and genetic disorders that target these faculties unevenly, such as a difficulty in recognizing faces (and facelike shapes) but not other objects, or a difficulty in reasoning about minds but not about objects or pictures. Similarly, Simon Baron-Cohen writes (1998, 335; my emphasis; see also Temple, 1997): I suggest that the study of mental retardation would profit from the application of the framework of cognitive neuropsychology (…). In cognitive neuropsychology,

It has been claimed that in the language systems of people with Williams syndrome (WS), syntax is intact but lexical memory is impaired. Evidence has come from past tense elicitation tasks with a small number of participants where individuals with WS are said to have a speci�c de�cit in forming irregular past tenses. However, typically developing children also show poorer performance on irregulars than regulars in these tasks, and one of the central features of WS language development is that it is delayed. We compared the performance of 21 participants with WS on two past tense elicitation tasks with that of four typically developing control groups, at ages 6, 8, 10, and adult. When verbal mental age was controlled for, participants in the WS group displayed no selective de�cit in irregular past tense performance. However, there was evidence for lower levels of generalisation to novel strings. This is consistent with the hypothesis that the WS language system is delayed because it has developed under different constraints, constraints that perhaps include atypical phonological representations. The Requests for reprints should be addressed to Michael Thomas or Annette Karmiloff-Smith,

It has been claimed that verbal short-term memory in Williams syndrome is characterised by an over-use of phonological coding alongside a reduced contribution of lexical semantics. We critically examine this hypothesis and present results from a memory span task comparing performance on concrete and abstract words, together with a replication of a span task using phonologically similar and phonologically dissimilar words. Fourteen participants with Williams syndrome were individually matched to two groups of typically developing children. The first control group was matched on digit span and the second on vocabulary level. Significant effects were found for both the semantic and the phonological variables in the WS group as well as in the control groups, with no interaction between experimental variable and group in either experiment. The results demonstrate that, despite claims to the contrary, children and adults with WS are able to access and make use of lexical semantics in a verbal short-term memory task in a manner comparable to typically developing individuals. Key words: Williams syndrome, short-term memory, language acquisition, phonology, semantics

Connectionist models have recently provided a concrete computational platform from which to explore how different initial constraints in the cognitive system can interact with an environment to generate the behaviors we find in normal development (Elman et al., 1996; Thomas & Karmiloff-Smith, 2002a). In this sense, networks embody several