Selective Revision

We introduce a constructive model of selective belief revision in which it is possible to accept only a part of the input information. A selective revision operator ο is defined by the equality K ο α = K * f(α), where * is an AGM revision operator and f a function, typically with the property ⊢ α → f(α). Axiomatic characterizations are provided for three variants of selective revision. This revised version was published online in June 2006 with corrections to the Cover Date.     

Providing Foundations for Coherentism

We prove that four theses commonly associated with coherentism are incompatible with the representation of a belief state as a logically closed set of sentences. The result is applied to the conventional coherence interpretation of the AGM theory of belief revision, which appears not to be tenable. Our argument also counts against the coherentistic acceptability of a certain form of propositional holism. We argue that the problems arise as an effect of ignoring the distinction between derived and non-derived beliefs, and we suggest that the kind of coherence relevant to epistemic justification is the coherence of non-derived beliefs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reversing the Levi identity

The AGM (Alchourrón-GÄrdenfors-Makinson) model of belief change is extended to cover changes on sets of beliefs that arenot closed under logical consequence (belief bases). Three major types of change operations, namely contraction, internal revision, and external revision are axiomatically characterized, and their interrelations are studied. In external revision, the Levi identity is reversed in the sense that onefirst adds the new belief to the belief base, and afterwards contracts its negation. It is argued that external revision represents an intuitively plausible way of revising one's beliefs. Since it typically involves the temporary acceptance of an inconsistent set of beliefs, it can only be used in belief representations that distinguish between different inconsistent sets of belief.     

The importance of impaired physical health and age in normal cognitive aging

The objective of this study was to investigate the importance of impaired physical health and age in normal cognitive aging. In our cross-sectional, clinical and explorative study, medical and neuropsychological data from 118 voluntary healthy controls aged 26-91 years were collected from five recruitment occasions. Health was assessed according to a criterion reflecting clinical and subclinical severity. The examinations included a clinical investigation, brain neuroimaging, and a comprehensive neuropsychological assessment. Regression analyses showed a significant incidence of clinical and subclinical medical disorders that explained 10.8% of the variation in cognitive performance, while age-related impairment explained 5.6%. Findings of the central nervous system were important but various other medical findings explained about half of the health-related variation. Cognitively demanding tasks were more susceptible to impaired physical health while tasks comprising salient motor- and visual spatial elements were more prone to be impaired by age. Our findings suggest (1) that impaired physical health is more important than chronological age in accounting for cognitive impairment across the adult lifespan, (2) that age and health dissociate with regard to cognitive functions affected, and (3) that selection for so-called "super healthy" elderly people might be justified in cognitive research. Because the prevalent diseases in normal aging are potentially preventable, the present findings promise good prospect for prevention of future cognitive disability among elderly people.     

Eradication

Eradication is a radical form of contraction that removes not only a sentence but also all of its non-tautological consequences from a belief set. Eradication of a single sentence that was included in the original belief set coincides with full meet contraction, but if the sentence is external to the belief set then the two operations differ. Multiple eradication, i.e. simultaneous eradication of several sentences, differs from full meet contraction even if the sentences to be contracted are all included in the original belief set. Eradication is axiomatically characterized and its properties investigated. It is shown to have close connections with the recovery postulate for multiple contraction. Based on these connections it is proposed that eradication rather than full meet contraction is the appropriate lower limiting case for multiple contraction operators.     

Recognition memory for emotional faces in amnestic mild cognitive impairment: An event-related potential study

ABSTRACT

This study examined the temporal course of emotional face recognition in amnestic mild cognitive impairment (aMCI). Patients and healthy controls (HC) performed a face recognition task, giving old/new responses to previously studied and novel faces displaying a negative or neutral expression. In aMCI patients, recognition accuracy was preserved for negative faces. Event-related potentials (ERPs) revealed disease-related changes in early perceptual components but not in ERP indices of explicit recognition. Specifically, aMCI patients showed impaired recognition effects for negative faces on the amplitudes of N170 and P2, suggesting deficient memory-related processing of negative faces at the stage of structural encoding and during an early recognition stage at which faces are individuated, respectively. Moreover, while a right-lateralized emotion effect specifically observed for correctly recognized faces on the amplitude of N170 was absent in aMCI, a similar emotion effect for successfully recognized faces on P2 was preserved in the patients, albeit with a different distribution. This suggests that in aMCI facilitated processing of successfully recognized emotional faces starts later in the processing sequence. Nonetheless, an early frontal old/new effect confined to negative faces and a parietal old/new effect unaffected by facial emotion were observed in both groups. This indicates that familiarity and conceptual priming processes may specifically contribute to recognition of negative faces in older adults and that aMCI patients can recruit the same retrieval mechanisms as controls, despite disease-related changes on early perceptual ERP components.     

Bootstrap Contraction

We can often specify how we would contract by a certain sentence by saying that this contraction would coincide with some other contraction that we know how to perform. We can for instance clarify that our contraction by p&q would coincide with our contraction by p, or by q, or by {p, q}. In a framework where the set of potential outcomes is known, some contractions are “self-evident” in the sense that there is only one serious candidate that can be the outcome of such a contraction. Contraction by a specific contractee (sentence or set of sentences to be contracted) is bootstrapped if it is specified by saying that it coincides with some such self-evident contraction. For a wide range of (multiple) contraction operators, contractions by any contractee can be bootstrapped. This means that the selection mechanism (selection function, incision function, etc.) can be replaced by a function called a bootstrapping selector that assigns to each contractee some “self-evident” contractee that yields the same outcome. With bootstrapping we can eliminate traditional extralogical components in contraction (e.g., selection functions) and replace them by bootstrapping selectors that reflect more closely the ways in which we actually reason and argue about belief contraction.     

Ideal Worlds — Wishful Thinking in Deontic Logic

The ideal world semantics of standard deontic logic identifies our obligations with how we would act in an ideal world. However, to act as if one lived in an ideal world is bad moral advice, associated with wishful thinking rather than well-considered moral deliberation. Ideal world semantics gives rise to implausible logical principles, and the metaphysical arguments that have been put forward in its favour turn out to be based on a too limited view of truth-functional representation. It is argued that ideal world semantics should be given up in favour of other, more plausible uses of possible worlds for modelling normative subject-matter.     

Category-specified Value Statements

A value statement such as “she is a good teacher” is categoryspecified, i.e., the criteria of evaluation are specified as those that are applicable to a given category, in this case the category of teachers. In this study of categoryspecified value statements, certain categories are identified that cannot be used to specify value aspects. Special attention is paid to categories that are constituted by functional characteristics. The logical properties of value statements that refer to such categories are shown to differ significantly from the corresponding properties in social choice theory.