Bart Geurts

Defeasible reasoning in high-functioning adults with autism: evidence for impaired exception-handling.

While autism is one of the most intensively researched psychiatric disorders, little is known about reasoning skills of people with autism. The focus of this study was on defeasible inferences, that is inferences that can be revised in the light of new information. We used a behavioral task to investigate (a) conditional reasoning and (b) the suppression of conditional inferences in high-functioning adults with autism. In the suppression task a possible exception was made salient which could prevent a conclusion from being drawn. We predicted that the autism group would have difficulties dealing with such exceptions because they require mental flexibility to adjust to the context, which is often impaired in autism. The findings confirm our hypothesis that high-functioning adults with autism have a specific difficulty with exception-handling during reasoning. It is suggested that defeasible reasoning is also involved in other cognitive domains. Implications for neural underpinnings of reasoning and autism are discussed.

Exceptions and anomalies: An ERP study on context sensitivity in autism

Several studies have demonstrated that people with ASD and intact language skills still have problems processing linguistic information in context. Given this evidence for reduced sensitivity to linguistic context, the question arises how contextual information is actually processed by people with ASD. In this study, we used event-related brain potentials (ERPs) to examine context sensitivity in high-functioning adults with autistic disorder (HFA) and Asperger syndrome at two levels: at the level of sentence processing and at the level of solving reasoning problems. We found that sentence context as well as reasoning context had an immediate ERP effect in adults with Asperger syndrome, as in matched controls. Both groups showed a typical N400 effect and a late positive component for the sentence conditions, and a sustained negativity for the reasoning conditions. In contrast, the HFA group demonstrated neither an N400 effect nor a sustained negativity. However, the HFA group showed a late positive component which was larger for semantically anomalous sentences than congruent sentences. Because sentence context had a modulating effect in a later phase, semantic integration is perhaps less automatic in HFA, and presumably more elaborate processes are needed to arrive at a sentence interpretation.

Reasoning with exceptions: An event-related brain potentials study

Defeasible inferences are inferences that can be revised in the light of new information. Although defeasible inferences are pervasive in everyday communication, little is known about how and when they are processed by the brain. This study examined the electrophysiological signature of defeasible reasoning using a modified version of the suppression task. Participants were presented with conditional inferences (of the type “if p, then q; p, therefore q”) that were preceded by a congruent or a disabling context. The disabling context contained a possible exception or precondition that prevented people from drawing the conclusion. Acceptability of the conclusion was indeed lower in the disabling condition compared to the congruent condition. Further, we found a large sustained negativity at the conclusion of the disabling condition relative to the congruent condition, which started around 250 msec and was persistent throughout the entire epoch. Possible accounts for the observed effect are discussed.

Specific indefinites, presupposition, and scope

This chapter argues that a number of expressions that are standardly categorized as pre-supposition inducers are better viewed as backgrounding devices. It presents a unified account of specificity and pre-supposition, which is based upon binding theory of pre-supposition. The binding theory is an extension of discourse representation theory, and consists of three principal claims: (1) anaphora is a species of pre-supposition, and that the standard pre-supposition-inducing expressions differ from pronominal anaphors mainly in that they possess a richer semantic content. (2) This difference explains why in general pre-supposition inducers, unlike anaphoric pronouns, can be interpreted by way of accommodation. (3) It is assumed that the process of presupposition projection is subject to certain constraints. The authors account improves upon Van Geenhovens proposal by giving a coherent picture of relation between specificity, and pre-supposition and definiteness, while foregoing the premise that indefinites are ambiguous between specific and non-specific readings. Keywords: binding theory; discourse representation theory; indefinites; non-specific readings; pre-supposition inducers; pronominal anaphors; specificity; Van Geenhoven

Layered Discourse Representation Theory

Layered Discourse Representation Theory (LDRT) is a general framework for representing linguistic content. Different types of content (e.g. asserted, presupposed, or implicated information) are separated by putting them on different layers, all of which have a model-theoretic interpretation, although not all layers are interpreted uniformly. It is shown how LDRT solves so-called `binding problems’, which tend to arise whenever different kinds of content are separated too strictly. The power of the framework is further illustrated by showing how various kinds of contextual information may be accommodated.

Overspecification of color, pattern, and size: salience, absoluteness, and consistency

The rates of overspecification of color, pattern, and size are compared, to investigate how salience and absoluteness contribute to the production of overspecification. Color and pattern are absolute and salient attributes, whereas size is relative and less salient. Additionally, a tendency toward consistent responses is assessed. Using a within-participants design, we find similar rates of color and pattern overspecification, which are both higher than the rate of size overspecification. Using a between-participants design, however, we find similar rates of pattern and size overspecification, which are both lower than the rate of color overspecification. This indicates that although many speakers are more likely to include color than pattern (probably because color is more salient), they may also treat pattern like color due to a tendency toward consistency. We find no increase in size overspecification when the salience of size is increased, suggesting that speakers are more likely to include absolute than relative attributes. However, we do find an increase in size overspecification when mentioning the attributes is triggered, which again shows that speakers tend to refer in a consistent manner, and that there are circumstances in which even size overspecification is frequently produced.

Interpreting focus again

How to respond to such a fine collection of commentaries which are, without exception, thorough, to the point, constructive, and full of suggestions for improvement? The best response by far would be a radical overhaul of the target article—but that is against the rules. The next-best thing would be a page-by-page discussion of each commentary separately—which the editor wouldn’t allow. So we have no choice but to make a selection of the many good points that have been raised, and hope against hope that we will manage not to distort them too much. The plan for the following discussion mirrors that of ‘Interpreting focus’ (IF). So we start with the main issue, concerning the association between focus and presupposition, then turn to focus particles, and conclude with a few remarks on it-clefts.

Monotonicity and syllogistic inference: a reply to Newstead

Newstead’s critique is an exercise in carpet-bombing: he doesn’t raise one big objection but a host of smaller ones. I hope I will be excused if I address only a handful. Let me start with a brief synopsis. Experimental investigations of human reasoning invariably use linguistic tasks. Subjects are to say whether this or that sentence follows from a given set of sentences, or to draw their own conclusions, etc. Hence, human reasoning, as studied by Newstead and his fellow psychologists, is at least partly a matter of linguistic processing. In particular, since inferences are drawn on the basis of what the premisses mean, human reasoning, as studied by psychologists, is at least partly a matter of semantic interpretation. We don’t know how big that part is, nor whether it can be neatly separated from “genuine” processes of inference (as is often assumed), but it is there. As interpretation precedes inference, it is only to be expected that reasoning is affected more by salient semantic properties than by others. By “salient” I mean such properties that play a prominent part in the interpretation of language. My paper explored the possibility that reasoning with quantifiers is influenced by what are known to be the salient properties of quantifying expressions, and especially by their monotonicity properties. In order to flesh out this suggestion, I presented a simple inference system, which was embedded in an equally simple processing model, with a view to showing “that even a crude processing model can produce reasonable predictions” (Geurts, 2003, p. 243). My idea was that if a toy model does reasonably well, a more sophisticated model is likely to do better.

Making Sense of Self Talk

People talk not only to others but also to themselves. The self talk we engage in may be overt or covert, and is associated with a variety of higher mental functions, including reasoning, problem solving, planning and plan execution, attention, and motivation. When talking to herself, a speaker takes devices from her mother tongue, originally designed for interpersonal communication, and employs them to communicate with herself. But what could it even mean to communicate with oneself? To answer that question, we need a theory of communication that explains how the same linguistic devices may be used to communicate with others and oneself. On the received view, which defines communication as information exchange, self talk appears to be an anomaly, for it is hard to see the point of exchanging information with oneself. However, if communication is analysed as a way of negotiating commitments between speaker and hearer, then communication may be useful even when speaker and hearer coincide. Thus a commitment-based approach allows us to make sense of self talk as well as social talk.