It is often assumed that similar domain-specific behavioural impairments found in cases of adult brain damage and developmental disorders correspond to similar underlying causes, and can serve as convergent evidence for the modular structure of the normal adult cognitive system. We argue that this correspondence is contingent on an unsupported assumption that atypical development can produce selective deficits while the rest of the system develops normally (Residual Normality), and that this assumption tends to bias data collection in the field. Based (...) on a review of connectionist models of acquired and developmental disorders in the domains of reading and past tense, as well as on new simulations, we explore the computational viability of Residual Normality and the potential role of development in producing behavioural deficits. Simulations demonstrate that damage to a developmental model can produce very different effects depending on whether it occurs prior to or following the training process. Because developmental disorders typically involve damage prior to learning, we conclude that the developmental process is a key component of the explanation of endstate impairments in such disorders. Further simulations demonstrate that in simple connectionist learning systems, the assumption of Residual Normality is undermined by processes of compensation or alteration elsewhere in the system. We outline the precise computational conditions required for Residual Normality to hold in development, and suggest that in many cases it is an unlikely hypothesis. We conclude that in developmental disorders, inferences from behavioural deficits to underlying structure crucially depend on developmental conditions, and that the process of ontogenetic development cannot be ignored in constructing models of developmental disorders. Key Words: Acquired and developmental disorders; connectionist models; modularity; past tense; reading. (shrink)

Public conversation about biological contributors to mental disorder often centers on whether the problem is “biological or not.” In this paper, we propose moving beyond this bifurcation to a very different question:how exactlyare these problems understood to be biological? Specifically, we consider four issues around which different interpretations of the body’s relationship to mental disorder exist:1. The body’s relationship to day-to-day action; 2. The extent to which the body is changeable; 3. The body’s relationship to context; 4. The degree to (...) which states of the body directly cause mental disorder.Drawing on the work of Merleau-Ponty and other phenomenologists, we examine different responses to these questions and associated implications for how mental health treatment and recovery come to be experienced. Finally, we consider broader questions these patterns raise, including why certain portrayals of the brain dominate public attention and how to foster more deliberation in this regard. (shrink)