David J. Chalmers

Conceptual Analysis and Reductive Explanation

Is conceptual analysis required for reductive explanation? If there is no a priori entailment from microphysical truths to phenomenal truths, does reductive explanation of the phenomenal fail? We say yes (Chalmers 1996; Jackson 1994, 1998). Ned Block and Robert Stalnaker say no (Block and Stalnaker 1999). A number of issues can be distinguished: (1) Is there an a priori entailment from microphysical truths to ordinary macroscopic truths? (2) If there is no a priori entailment from microphysical truths to phenomenal truths, does reductive explanation of the phenomenal fail? (3) If there is no a priori entailment from microphysical truths to phenomenal truths, is physicalism about the phenomenal false? (4) Is there an a priori entailment from microphysical truths to phenomenal truths? We hold that the first three questions should be answered positively (with some qualifications to be outlined). Block and Stalnaker hold that the first three questions should be answered negatively. Their central strategy is to argue for a negative answer to the first question, and to use this conclusion to argue for a negative answer to the second and third questions. They argue that truths about water and about life, for example, are not entailed a priori by microphysical truths, but that this is no bar to the reductive explanation and physical constitution of water and of life. In this paper, we will address Block and Stalnakers arguments for a negative answer to the first three questions, while remaining neutral on the fourth. We will proceed by first giving an independent defense of a positive answer to the first question. This makes the ensuing reply to Block and Stalnaker more straightforward, and also makes the discussion accessible to those unfamiliar with the literature.

High-level perception, representation, and analogy: a critique of artificial intelligence methodology

Abstract High-level perception—the process of making sense of complex data at an abstract, conceptual level—is fundamental to human cognition. Through high-level perception, chaotic environmental stimuli are organized into mental representations that are used throughout cognitive processing. Much work in traditional artificial intelligence has ignored the process of high-level perception, by starting with hand-coded representations. In this paper, we argue that this dismissal of perceptual processes leads to distorted models of human cognition. We examine some existing artificial-intelligence models—notably BACON, a model of scientific discovery, and the Structure-Mapping Engine, a model of analogical thought—-and argue that these are flawed precisely because they downplay the role of high-level perception. Further, we argue that perceptual processes cannot be separated from other cognitive processes even in principle,and therefore that traditional artificial-intelligence models cannot be defended by supp...

Syntactic Transformations on Distributed Representations

There has been much interest in the possibility of connectionist models whose representations can be endowed with compositional structure, and a variety of such models have been proposed. These models typically use distributed representations that arise from the functional composition of constituent parts. Functional composition and decomposition alone, however, yield only an implementation of classical symbolic theories. This paper explores the possibility of moving beyond implementation by exploiting holistic structure-sensitive operations on distributed representations. An experiment is performed using Pollack’s Recursive Auto-Associative Memory (RAAM). RAAM is used to construct distributed representations of syntactically structured sentences. A feed-forward network is then trained to operate directly on these representations, modeling syntactic transformations of the represented sentences. Successful training and generalization is obtained, demonstrating that the implicit structure present in these representations can be used for a kind of structure-sensitive processing unique to the connectionist domain.

The Evolution of Learning: An Experiment in Genetic Connectionism

This paper explores how an evolutionary process can produce systems that learn. A general framework for the evolution of learning is outlined, and is applied to the task of evolving mechanisms suitable for supervised learning in single-layer neural networks. Dynamic properties of a networks information-processing capacity are encoded genetically, and these properties are subjected to selective pressure based on their success in producing adaptive behavior in diverse environments. As a result of selection and genetic recombination, various successful learning mechanisms evolve, including the well-known delta rule. The effect of environmental diversity on the evolution of learning is investigated, and the role of different kinds of emergent phenomena in genetic and connectionist systems is discussed.

Rugby Union Injuries to the Cervical Spine and Spinal Cord

AbstractInjuries to the cervical spine are among the most serious injuries occurring as a result of participation in rugby. Outcomes of such injuries range from complete recovery to death, depending on the degree of spinal cord damage sustained. Much information has been gained regarding the mechanisms and frequency of such injuries, from case reports and case series studies. The most commonly reported mechanism of injury has been hyperflexion of the cervical spine, resulting in fracture dislocation of C4-C5 or C5-C6. Tracking both the trends of incidence of spinal injuries, and the effectiveness of injury prevention initiatives has proved difficult because of a lack of properly conducted epidemiological studies.Within the constraints of the research published to date, it appears that hookers and props have been at disproportionate risk of cervical spine injury, predominantly because of injuries sustained during scrummaging. While the scrum was the phase of play most commonly associated with spinal injuries throughout the 1980s in most rugby playing countries, there has been a trend through the 1990s of an increasing proportion of spinal injuries occurring in the tackle situation. The majority of injuries have occurred early in the season, when grounds tend to be harder, and players are lacking both practice and physical conditioning for the physical contact phases of the sport.A number of injury prevention measures have been launched, including changes to the laws of the game regarding scrummaging, and education programmes aimed at enforcing safe techniques and eliminating illegal play. Calls for case-registers and effective epidemiological studies have been made by researchers and physicians in most countries where rugby is widespread, but it appears to be only recently that definite steps have been made towards this goal. Well-designed epidemiological studies will be able to provide more accurate information about potential risk factors for injury such as age, grade, position, gender and ethnicity. Research into the long-term effects of participation in rugby on the integrity of the spinal column is warranted.

Does a rock implement every finite-state automaton?

Hilary Putnam has argued that computational functionalism cannot serve as a foundation for the study of the mind, as every ordinary open physical system implements every finite-state automaton. I argue that Putnams argument fails, but that it points out the need for a better understanding of the bridge between the theory of computation and the theory of physical systems: the relation of implementation. It also raises questions about the class of automata that can serve as a basis for understanding the mind. I develop an account of implementation, linked to an appropriate class of automata, such that the requirement that a system implement a given automaton places a very strong constraint on the system. This clears the way for computation to play a central role in the analysis of mind.

The New Zealand rugby injury and performance project. VI. A prospective cohort study of risk factors for injury in rugby union football

Objectives—Although the nature of rugby injury has been well documented, little is known about key risk factors. A prospective cohort study was undertaken to examine the association between potential risk factors and injury risk, measured both as an injury incidence rate and as a proportion of the playing season missed. The latter measure incorporates a measure of injury severity. Methods—A cohort of 258 male players (mean (SD) age 20.6 (3.7) years) were followed through a full competitive season. At a preseason assessment, basic characteristics, health and lifestyle patterns, playing experience, injury experience, training patterns, and anthropometric characteristics were recorded, and then a battery of fitness tests were carried out. Results—A multiple regression model identified grade and previous injury experience as risk factors for in season injury, measured as an injury incidence rate. A second model identified previous injury experience, hours of strenuous physical activity a week, playing position, cigarette smoking status, body mass index, years of rugby participation, stress, aerobic and anaerobic performance, and number of push ups as risk factors for in season injury, measured as proportion of season missed. Conclusions—The findings emphasise the importance of previous injury as a predictor of injury incidence and of missing play. They also show the importance of considering both the incidence rate and severity of injury when identifying risk factors for injury in sport.

Height and surfacing as risk factors for injury in falls from playground equipment: a case-control study.

OBJECTIVES: Despite the widespread promotion of safety standards no epidemiological studies have adequately evaluated their effectiveness in preventing injury in falls from playground equipment. This study evaluated the effectiveness of the height and surfacing requirements of the New Zealand standard for playgrounds and playground equipment. SETTING: Early childhood education centres and schools in two major cities in the South Island of New Zealand. METHODS: Data were collected on 300 children aged 14 years or less who had fallen from playground equipment. Of these, 110 (cases) had sustained injury and received medical attention, while 190 (controls) had not sustained injury requiring medical attention. RESULTS: Logistic regression models fitted to the data indicated that the risk of injury being sustained in a fall was increased if the equipment failed to comply with the maximum fall height (odds ratio (OR) = 3.0; 95% confidence interval (CI) 0.7 to 13.1), surfacing (OR = 2.3; 95% CI 1.0 to 5.0), or safe fall height (OR = 2.1; 95% CI 1.1 to 4.0) requirements. Falls from heights in excess of 1.5 metres increased the risk of injury 4.1 times that of falls from 1.5 metres or less and it was estimated that a 45% reduction in children attending emergency departments could be achieved if the maximum fall height was lowered to 1.5 metres. CONCLUSIONS: Although the height and surfacing requirements of the New Zealand standard are effective in preventing injury in falls from playground equipment, consideration should be given to lowering the maximum permissible fall height to 1.5 metres.

Injury prevention in sport: not yet part of the game?

Background: There is a saying in sport that “injury is just part of the game”. In other words, injury in sport is seen as inevitable. Objective: To examine progress toward reaching the contrary position that “injury prevention is just part of the game”. Methods: The four steps of van Mechelen’s “sequence of prevention” model provide a structure for examining progress. Results: What is known about the size of the problem (step 1)? Most is known about more serious injuries and about injuries in élite and professional sport. Least is known about less serious injuries, injury in community level and amateur sport, and injury occurring in recreational activities. What is known about risk factors (step 2)? Despite calls for analytic studies since the early 1980s, few such studies have been reported in the literature. What is known about the effectiveness of preventive measures (step 3)? Few randomized controlled trials have been reported in the literature. Are there systems in place to monitor sports injury (step 4)? Examples are given of systems in North America, Europe, and Australasia. Conclusions: With a few exceptions, progress has not gone beyond step 1 in van Mechelen’s model. Challenges for the future include: deciding where research efforts should be placed, standardization of definitions and methods of data collection and reporting, identification of risk factors and mechanisms of injury, and the evaluation of interventions. Finally, if the field of sports injury prevention is to advance, multidisciplinary collaboration will be required, along with the involvement of the sports community.

Some Audiological, Psychological, Educational and Behavioral Characteristics Of Children With Bilateral Otitis Media With Effusion: A Longitudinal Study

This paper describes a longitudinal study of a group of children who had bilateral otitis media with effusion at age five and who were compared with a group of children with normal ears at that age. OME was defined as Type B tympanograms and features of OME by otomicroscopic examination and normal as Type A tympanograms in both ears again confirmed by otomicroscopy. Results are reported for hearing (ages 5, 7, 9, 11), intelligence (3, 5, 7, 9, 11), language development (3, 5, 7, 9), speech articulation (5, 7, 9), reading attainment (7, 9, 11), and behaviour problems (5, 7, 9, 11). Children with bilateral OME at age five had a moderately high degree of hearing loss at that age and continued to have a significant degree of hearing loss at subsequent ages. The degree of later hearing loss was small. When the mean IQs over the years were combined, there was no significant difference between the groups. The bilateral OME group gained significantly lower average scores in both verbal comprehension and expression. Also, the combined speech articulation and the reading test scores were significantly lower in the bilateral OME group. Teachers, but not parents, reported significantly more behaviour problems in the bilateral OME group over the period studied. Because this was the first longitudinal study of what was assumed to be the consequences of bilateral OME to be reported, further such research is recommended. In the meantime, the results were interpreted as supporting the hypothesis that bilateral OME has long term adverse effects on children and that current efforts towards the early identification and treatment of bilateral OME should be continued. These efforts, however, should be targeted well before age five and possibly prior to age three.