Reasoning About Collectively Accepted Group Beliefs

A proof-theoretical treatment of collectively accepted group beliefs is presented through a multi-agent sequent system for an axiomatization of the logic of acceptance. The system is based on a labelled sequent calculus for propositional multi-agent epistemic logic with labels that correspond to possible worlds and a notation for internalized accessibility relations between worlds. The system is contraction- and cut-free. Extensions of the basic system are considered, in particular with rules that allow the possibility of operative members or legislators. Completeness with respect to the underlying Kripke semantics follows from a general direct and uniform argument for labelled sequent calculi extended with mathematical rules for frame properties. As an example of the use of the calculus we present an analysis of the discursive dilemma.     

The evolution of alexia in two cases of posterior cortical atrophy

Posterior cortical atrophy (PCA) is an uncommon presentation of Alzheimer's disease (AD), characterised by prevalent anatomo-functional involvement of posterior cortical areas. Accordingly, the main clinical features at onset are disorders of high-order visual processing, such as alexia and impairments of visuo-spatial and visuo-constructional abilities. The clinical features in the early stages of disease are variable, and they have been suggested to stem from prevalent ventral or dorsal brain pathology, and/or asymmetric hemispheric involvement. With disease progression, these differences tend to blur with the increasing severity of neuropsychological dysfunction. We report two PCA patients showing different patterns of reading impairment (respectively, letter-by-letter reading and neglect dyslexia). A follow-up study suggested that the qualitative features of alexia remain distinctive with disease evolution. In addition, single photon emission tomography (SPECT) studies revealed different patterns of hypoperfusion, consistent with the alexia types. A careful reading assessment can provide important insights to the pattern of progression of the disease in patients with PCA up to the late stages of the pathology.     

Developmental changes in the weighting of prosodic cues

Previous research has shown that the weighting of, or attention to, acoustic cues at the level of the segment changes over the course of development (Nittrouer & Miller, 1997; Nittrouer, Manning & Meyer, 1993). In this paper we examined changes over the course of development in weighting of acoustic cues at the suprasegmental level. Specifically, we tested English-learning 4-month-olds' performance on a clause segmentation task when each of three acoustic cues to clausal units was neutralized and contrasted it with performance on a Baseline condition where no cues were manipulated. Comparison with the reported performance of 6-month-olds on the same task (Seidl, 2007) reveals that 4-month-olds weight prosodic cues to clausal boundaries differently than 6-month-olds, relying more heavily on all three correlates of clausal boundaries (pause, pitch and vowel duration) than 6-month-olds do, who rely primarily on pitch. We interpret this as evidence that 4-month-olds use a holistic processing strategy, while 6-month-olds may already be able to attend separately to isolated cues in the input stream and may, furthermore, be able to exploit a language-specific cue weighting. Thus, in a way similar to that in other cognitive domains, infants begin as holistic auditory scene processors and are only later able to process individual auditory cues.     

Varieties of Linear Calculi

A uniform calculus for linear logic is presented. The calculus has the form of a natural deduction system in sequent calculus style with general introduction and elimination rules. General elimination rules are motivated through an inversion principle, the dual form of which gives the general introduction rules. By restricting all the rules to their single-succedent versions, a uniform calculus for intuitionistic linear logic is obtained. The calculus encompasses both natural deduction and sequent calculus that are obtained as special instances from the uniform calculus. Other instances give all the invertibilities and partial invertibilities for the sequent calculus rules of linear logic. The calculus is normalizing and satisfies the subformula property for normal derivations.     

Finger-digit compatibility in Arabic numeral processing

Finger-digit response compatibility was tested by asking participants to identify Arabic digits by pressing 1 of 10 keys with all 10 fingers. The direction of the finger-digit mapping was varied by manipulating the global direction of the hand-digit mapping as well as the direction of the finger-digit mapping within each hand (in each case, from small to large digits, or the reverse). The hypothesis of a left-to-right mental number line predicted that a complete left-to-right mapping should be easier whereas the hypothesis of a representation based on finger counting predicted that a counting-congruent mapping should be easier. The results show that when all 10 fingers are used to answer, a mapping congruent with the prototypical finger-counting strategy reported by the participants leads to better performance than does a mapping congruent with a left-to-right oriented mental number line, both in palm-down and palm-up postures of the hands, and they demonstrate that finger-counting strategies influence the way that numerical information is mentally represented and processed.     

Horizontal and vertical Simon effect: different underlying mechanisms?

Reaction times are usually faster when stimulus and response occur at the same location than when they do not, even if stimulus location is irrelevant to the task (Simon effect). This effect was found with both horizontal and vertical stimulus-response arrangements. The same mechanisms have been proposed to be involved in either case. Here, we compared a horizontal and a vertical Simon task by means of a RT time-course analysis of the Simon effect. Also, we analysed the lateralised readiness potential (LRP), an index of covert response-preparation processes. In the horizontal task, the Simon effect decays over time and pre-activation occurs above the motor cortex ipsilateral to the stimulus. In contrast, the Simon effect does not decay over time and no early incorrect LRP deflection is observed in the vertical task. These findings suggest that typical activation accounts can fit only the horizontal Simon effect, while a translation explanation is more suitable for the vertical Simon effect.     

Crossmodal object-based attention: auditory objects affect visual processing

According to the object-based view, visual attention can be deployed to "objects" or perceptual units, regardless of spatial locations. Recently, however, the notion of object has also been extended to the auditory domain, with some authors suggesting possible interactions between visual and auditory objects. Here we show that task-irrelevant auditory objects may affect the deployment of visual attention, providing evidence that crossmodal links can also occur at an object-based level. Hence, in addition to the well documented control of visual objects over what we hear, our findings demonstrate that, in some cases, auditory objects can affect visual processing.     

Automatic and voluntary focusing of attention

In this study, we investigate whether attentional focusing, like attentional orienting, comprises two independent mechanisms. We provide direct empirical evidence in favor of the existence of two mechanisms--one exogenous, or automatic, and one endogenous, or voluntary--that play a role in adjusting the size of the focus of attention. When a new object suddenly occurs in the visual field, the focus is first automatically fitted to it, and then an endogenous effort has to be exerted to maintain attention in the focused mode. Also, we provide evidence that voluntary focusing needs a perceptual object in order to operate.     

The role of long-term-memory and short-term-memory links in the Simon effect

In Experiment 1, children performed a Simon task after a spatially compatible or incompatible task. Results showed a Simon effect after the spatially compatible task and a reversed Simon effect after the spatially incompatible task. In Experiments 2-5, an identical procedure was adopted with adult participants, who performed the Simon task immediately after, a day after, or a week after the spatial compatibility task. Experiment 6 established a baseline for the Simon effect. Results showed a Simon effect after the spatially compatible task and no Simon effect or a reversed Simon effect after the spatially incompatible task. A modified version of the computational model of M. Zorzi and C. Umiltà (1995) was used to compare possible accounts of the findings. The best account exploits 2 types of short-term-memory links between stimulus and response and their interaction with long-term-memory links.