Thought, language and mental representation Jonathan Trigg (jon.trigg@louisiana.edu) Program in Philosophy, UL Lafayette Lafayette, LA 70504 USA Michael Kalish (kalish@louisiana.edu) Institute of Cognitive Science, UL Lafayette Lafayette, LA 70504 USA believe, is not a direction cognitive scientists should be reluctant to travel in; for it takes us further and further away from Cartesian conceptions of mentality that can only hamstring research. Abstract We examine the proposal that thinking is a combinatorial operation on mental representations, and argue that it cannot be. If the argument is successful it shows that cognitive science cannot explain intelligent linguistic behavior by explaining what thinking is. We point out that this does not impugn the practice of cognitive scientists interested in human language, which, properly understood, consists in the framing and testing of hypotheses about the causally necessary enabling conditions of intelligent linguistic behavior. Keywords: Wittgenstein; thought, representation, language of thought. language, Overview of the argument and some preliminary points. The argument we present here starts with the premise that to think that something is so is to perform combinatorial operations on representations, and it moves to the negative conclusion that to think that something is so cannot be to perform combinatorial operations on mental representations. This should not be taken to imply that thinking is a combinatorial operation on non-mental representations like words and sentences. Certain cases of thinking may be that 1 , but there is nothing in the argument which entails the strong view that to think is to speak silently to oneself in a natural language. The aim is only to rule out a widely held view about what thinking is, not to defend a competing one. The view that is ruled out is that for Sam to judge that ducks run is for her to perform an operation on representations of a radically different kind than those on which she would operate were she to make a corresponding assertion. On such a view when she asserts that ducks run, operations are performed on two sorts of representation, one mental one not; and when she judges that ducks run but asserts nothing they are performed only on mental representations. On this sort of view internal mental representing need not be connected to external spoken representing in any way; so what a creature can say sets no limits on what it can think. If the argument of this paper is successful we will have shown that it can‟t be because linguistic behaviour is linked with hidden events and processes that it counts as linguistic. This is liable to upset very widely held assumptions both about the nature of thinking and about the shape of cognitive scientific explanations. On these assumptions, what is important about Sam‟s assertion that ducks run is how it stands to various items or events in, or states of, her brain. Illuminating explanations will consist in claims about this standing. That implies a certain conception of what makes assertions into meaningful speech acts and differentiates them from grunts and squawks. On it, for Sam mental Introduction We regard understanding as the essential thing, and signs as something inessential. (Wittgenstein, 1974) ...the limits of possible thought are the limits of the possible expression of thought. (Bennett & Hacker, 2003) If strong Wittgensteinian cross currents still ran into the mainstream of contemporary philosophy of mind and language, these philosophical waters would be much more turbulent than they now are. Indeed it is not even clear that they would be running in roughly their present direction. As things stand the river flows wide and slow, almost undisturbed by substantial impediments to its progress, and serious attempts to change its course are liable to seem naive or over ambitious – uncomprehending of the forces at work. The argument we present here, which is Wittgensteinian in spirit, is meant to push quite hard against the prevailing drift. It‟s an argument to the conclusion that thinking is not mental representing and thoughts are not mental representations. We are not, by any means, the first to make this sort of argument. Indeed, on a plausible reading of his two great works, the very theory Wittgenstein (1921/2001) defends in the Tractatus is the theory he repudiates in the Philosophical Investigations (Wittgenstein, 1958), and at its heart is the thesis that thinking is mental representing. Our aim here is to say precisely what it is about the claim that thoughts are mental representations (and that thinking is mental representing) that runs counter to the direction in which Wittgenstein‟s later arguments lead. This, we Bennett & Hacker (2003) contains an excellent series of reminders of how many different things we ordinarily call thinking.
Languages are transmitted from person to person and generation to generation via a process of iterated learning: people learn a language from other people who once learned that language themselves. We analyze the consequences of iterated learning for learning algorithms based on the principles of Bayesian inference, assuming that learners compute a posterior distribution over languages by combining a prior (representing their inductive biases) with the evidence provided by linguistic data. We show that when learners sample languages from this posterior distribution, iterated learning converges to a distribution over languages that is determined entirely by the prior. Under these conditions, iterated learning is a form of Gibbs sampling, a widely-used Markov chain Monte Carlo algorithm. The consequences of iterated learning are more complicated when learners choose the language with maximum posterior probability, being affected by both the prior of the learners and the amount of information transmitted between generations. We show that in this case, iterated learning corresponds to another statistical inference algorithm, a variant of the expectation-maximization (EM) algorithm. These results clarify the role of iterated learning in explanations of linguistic universals and provide a formal connection between constraints on language acquisition and the languages that come to be spoken, suggesting that information transmitted via iterated learning will ultimately come to mirror the minds of the learners.
Human immunodeficiency virus type 1 (HIV-1) isolates recovered from infected children in Romania were characterized for their biologic, serologic, and molecular properties. The isolates were from subjects in different clinical states, and all showed cytopathic properties in peripheral blood mononuclear cells and varying kinetics of replication. The isolates grew to varying titers in macrophages and established T cell lines. Serologic evaluation with Romanian sera indicated stronger antibody response to the gp120 of Romanian isolates than to the envelope protein of HIV-1 isolates from other countries. Although there was cross-neutralization among the Romanian isolates, no substantial activity was noted against HIV-1 prototype strains from the United States, Africa, and Thailand. Genetic analysis of the envelope C2-V3 region strongly suggests that the Romanian isolates are a subtype distinct from those assigned to other HIV-1 strains analyzed to date. This finding raises questions about the origin of HIV-1 in Romania.
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