Computation,hypercomputation, and physical science

Copeland and others have argued that the Church–Turing thesis (CTT) has been widely misunderstood by philosophers and cognitive scientists. In particular, they have claimed that CTT is in principle compatible with the existence of machines that compute functions above the “Turing limit,” and that empirical investigation is needed to determine the “exact membership” of the set of functions that are physically computable. I argue for the following points: (a) It is highly doubtful that philosophers and cognitive scientists have widely misunderstood CTT as alleged.¹ In fact, by and large, computability theorists and mathematical logicians understand CTT in the exact same way. (b) That understanding most likely coincides with what Turing and Church had in mind. Even if it does not, an accurate exegesis of Turing and Church need not dictate how today's working scientists understand the thesis. (c) Even if we grant Copeland's reading of CTT, an orthodox stronger version of it which he rejects (Gandy's thesis) follows readily if we only accept a highly plausible necessary condition for what constitutes a deterministic digital computer. Finally, (d) regardless of whether we accept this condition, the prospects for a scientific theory of hypercomputation are exceedingly poor because physical science does not have the wherewithal to investigate computability or to discover its ultimate “limit.”     

Computation, reduction, and teleology of consciousness

This paper aims to explore mechanistic and teleological explanations of consciousness. In terms of mechanistic explanations, it critiques various existing views, especially those embodied by existing computational cognitive models. In this regard, the paper argues in favor of the explanation based on the distinction between localist (symbolic) representation and distributed representation (as formulated in the connectionist literature), which reduces the phenomenological difference to a mechanistic difference. Furthermore, to establish a teleological explanation of consciousness, the paper discusses the issue of the functional role of consciousness on the basis of the aforementioned mechanistic explanation. A proposal based on synergistic interaction between the conscious and the unconscious is advanced that encompasses various existing views concerning the functional role of consciousness. This two-step deepening explanation has some empirical support, in the form of a cognitive model and various cognitive data that it captures.     

Computation and Causation

The computer's effect on our understanding of causation has been enormous. By the mid-1980s, philosophical and social-scientific work on the topic had left us with (1) no reasonable reductive account of causation and (2) a class of statistical causal models tied to linear regression. At this time, computer scientists were attacking the problem of equipping robots with models of the external that included probabilistic portrayals of uncertainty. To solve the problem of efficiently storing such knowledge, they introduced Bayes Networks and directed graphs. By attaching a causal interpretation to Bayes Networks, the philosophy of causation changed dramatically. We are now able to be extremely general about how causal structure connects to data, and systematic about when causal structures are empirically indistinguishable. In this essay I try to motivate and describe this synthesis.     

Rationality,function, and content

Conclusions To summarize, in order for rational agents to be able to engage in the sophisticated kinds of reasoning exemplified by human beings, they must be able to introspect much of their cognition. The problem of other minds and the problem of knowing the mental states of others will arise automatically for any rational agent that is able to introspect its own cognition. The most that a rational agent can reasonably believe about other rational agents is that they have rational architectures similar to its own, and that they have thoughts related to their rational architectures in certain ways. This leads to Rational Functionalism as an account of what it is to be a cognizer having mental states. That in turn entails that a computer can be a person in precisely the same sense as my next door neighbor if it can appropriately mimic my rational architecture. There is nothing I could know about my neighbor that I could not believe with equal justification about the computer. Rational Functionalism also makes it reasonable to define the narrow content of a thought to be its overall place in the agent's rational architecture, that is, its conceptual role. This is, however, avery narrow notion of content. For practical purposes, we are not interested in knowing the narrow contents of other people's thoughts. We are only interested in rather general properties of those narrow contents. This is what is expressed by the use ofthat-clauses in public language.This is a reply to the comments by Stephen Schiffer and Robert Cummins on my bookHow to Build a Person (Bradford/MIT Press, 1989). These papers were presented at the Pacific Division meeting of the American Philosophical Association in San Francisco, March, 1991. Cummins paper appears in this volume, and Schiffer's paper will appear inPhilosophy and Phenomenlogical Research.     

A moratorium on cyborgs: Computation,cognition, and commerce

By examining the contingent alliance that has emerged between the computational theory of mind and cyborg theory, we discern some questionable ways in which the literalization of technological metaphors and the over-extension of the “computational” have functioned, not only to influence conceptions of cognition, but also by becoming normative perspectives on how minds and bodies should be transformed, such that they can capitalize on technology’s capacity to enhance cognition and thus amend our sense of what it is to be “human”. We consider “a moratorium on cyborg discourse” as a way of focusing the conceptual and social–political problems posed by this alliance.     

Context,content, and relativism

This paper argues against relativism, focusing on relativism based on the semantics of predicates of personal taste. It presents and defends a contextualist semantics for these predicates, derived from current work on gradable adjectives. It then considers metasemantic questions about the kinds of contextual parameters this semantics requires. It argues they are not metasemantically different from those in other gradable adjectives, and that contextual parameters of this sort are widespread in natural language. Furthermore, this paper shows that if such parameters are rejected, it leads to an unacceptably rampant form of relativism, that relativizes truth to an open-ended list of parameters.

Concept empiricism, content, and compositionality

Concepts are the constituents of thoughts. Therefore, concepts are vital to any theory of cognition. However, despite their widely accepted importance, there is little consensus about the nature and origin of concepts. Thanks to the work of Lawrence Barsalou, Jesse Prinz and others concept empiricism has been gaining momentum within the philosophy and psychology literature. Concept empiricism maintains that all concepts are copies, or combinations of copies, of perceptual representations—that is, all concepts are couched in the codes of perceptual representation systems. It is widely agreed that any satisfactory theory of concepts must account for how concepts semantically compose (the compositionality requirement) and explain how their intentional content is determined (the content determination requirement). In this paper, I argue that concept empiricism has serious problems satisfying these two requirements. Therefore, although stored perceptual representations may facilitate some traditionally conceptual tasks, concepts should not be identified with copies of perceptual representations.     

Multiple Realization,Computation and the Taxonomy of Psychological States

The paper criticizes standard functionalist arguments for multiple realization. It focuses on arguments in which psychological states are conceived as computational, which is precisely where the multiple realization doctrine has seemed the strongest. It is argued that a type-type identity thesis between computational states and physical states is no less plausible than a multiple realization thesis. The paper also presents, more tentatively, positive arguments for a picture of local reduction.     

MV-Algebras and Quantum Computation

We introduce a generalization of MV algebras motivated by the investigations into the structure of quantum logical gates. After laying down the foundations of the structure theory for such quasi-MV algebras, we show that every quasi-MV algebra is embeddable into the direct product of an MV algebra and a “flat” quasi-MV algebra, and prove a completeness result w.r.t. a standard quasi-MV algebra over the complex numbers. Presented by Heinrich Wansing     

定量数据分析效应值:意义、计算与解释

由于零假设显著性检验存在的问题,近年来国外许多研究者、期刊编辑和研究学会建议或要求定量研究结果报告效应值作为对显著性检验结果的补充,然而国内心理学、教育学等社会科学领域还很少有学者对效应值进行专门研究。文章将讨论显著性检验存在的问题,效应值的定义及其重要性,效应值的分类、效应值的计算方法和效应值的解释标准。     

Colour vision,evolution, and perceptual content

Computational models of colour vision assume that the biological function of colour vision is to detect surface reflectance. Some philosophers invoke these models as a basis for externalism about perceptual content (content is distal) and objectivism about colour (colour is surface reflectance). In an earlier article (Thompson et al. 1992), I criticised the computational objectivist position on the basis of comparative colour vision: There are fundamental differences among the colour vision of animals and these differences do not converge on the detection of any single type of environmental property. David R. Hilbert (1992) has recently defended computational objectivism against my comparative argument; his arguments are based on the externalist approach to perceptual content originally developed by Mohan Matthen (1988) and on the computationally inspired theory of the evolutionary basis for trichromacy developed by Roger N. Shepard (1990). The present article provides a reply to Hilbert with extensive criticism of both Matthen's and Shepard's theories. I argue that the biological function of colour vision is not to detect surface reflectance, but to provide a set of perceptual categories that can apply to objects in a stable way in a variety of conditions. Comparative research indicates that both the perceptual categories and the distal stimuli will differ according to the animal and its visual ecology, therefore externalism and objectivism must be rejected.Versions of this article were read to the Department of Philosophy at the University of Chicago and to the Department of Philosophy at Boston University. I am grateful to the audiences for the discussions that ensued. I am also grateful to an anonymous referee for constructive criticism of certain points in the article. Special thanks are due to my comparative colour vision collaborators, Adrian Palacios and Francisco Varela.     

Motive-related memories: content, structure, and affect

Two studies tested hypotheses on the content and structure of autobiographical memories and the affect linked to them. In Study 1, agentic- and communal-motivated individuals recorded their most memorable experiences and completed the PANAS each day for 6 weeks. Memories were coded for content and structure. Agentics and communals reported more motive congruent memories, and their congruent memories were structured using more differentiation and integration, respectively. In addition, agentics had slightly higher PA and lower NA scores. In Study 2, agentics and communals recalled an event pertaining to either social separation or connection and then completed an affect measure of agentic and communal items. Agentics recalled more agentic memories in the separation condition and communals recalled more communal memories in the connection condition. Complexity analyses showed that agentics and communals used differentiation and integration respectively to recall their motive-congruent memories. The affect data showed a modestpredicted pattern. Results suggest that implicit motives have an impact on autobiographical memory but are not as clearly related to self-report affect measures, possibly due to method variance.