Model checking propositional dynamic logic with all extras

This paper presents a model checking algorithm for Propositional Dynamic Logic (PDL) with looping, repeat, test, intersection, converse, program complementation as well as context-free programs. The algorithm shows that the model checking problem for PDL remains PTIME-complete in the presence of all these operators, in contrast to the high increase in complexity that they cause for the satisfiability problem.     

Relationships between anger, symptoms, and cognitive factors in OCD checkers

The purpose of this study was to examine whether individuals diagnosed with obsessive-compulsive disorder (OCD) with primary checking compulsions report higher levels of trait anger and anger expression compared with a student control group, and whether trait anger and anger expression are correlated with specific beliefs and interpretations that are common among individuals who compulsively check. A group of individuals with OCD reporting significant checking compulsions (n=33) and a group of undergraduate students (n=143) completed a questionnaire package that included measures of trait anger and anger expression, as well as measures of obsessive-compulsive symptoms and beliefs. The compulsive checking group reported greater trait anger, though not greater anger expression, than the student control group. Furthermore, beliefs concerning perfectionism and intolerance of uncertainty were positively correlated with anger expression and trait anger among compulsive checkers but not among the student control group. The implications of these findings are discussed in terms of cognitive-behavioural treatments for and models of compulsive checking in OCD.     

The computational complexity of scenario-based agent verification and design

We first advocate that the AUML (Agent Unified Modeling Language) notation, even in its new version, is not precise enough to adequately describe protocols. This problem was long identified by Harel and we propose to follow his solution: extend sequence diagrams with a “prechart”, i.e. single out the initiation sequence of the protocol. This new notation keeps readability and intuition, but is also technically adequate and is given a formal semantics. It actually is a form of simple temporal logics, equipped with a game-based semantics, which is appropriate for modeling agent-based systems. We then go on to study its complexity. Unsurprisingly, the version with protocol roles is undecidable. The main interesting problem is to synthesize agents that follow the protocol described. Surprisingly, it is undecidable even if we remove roles, alternatives, loops, asynchronous communication, conditions, constraints, negations (already removed in AUML). The complexity of checking whether a society of agents obeys a protocol given in this trivial notation is also surprisingly high: it is PSPACE-complete, like temporal logic, while we show that this simple language is strongly less expressive than temporal logic. Notations in-between have the expected increase in expressiveness, but no increase in complexity. This justifies the use of a language including alternatives, asynchronous communication and conditions, since it increases expressiveness with no cost in complexity.     

Adaptive Model Checking

We consider the case where inconsistencies are present betweena system and its corresponding model, used for automatic verification.Such inconsistencies can be the result of modeling errors orrecent modifications of the system. Despite such discrepancies,we can still attempt to perform automatic verification. In fact,as we show, we can sometimes exploit the verification resultsto assist in automatically learning the required updates tothe model. In a related previous work, we have suggested theidea of black box checking, where verification starts withoutany model, and the model is obtained while repeated verificationattempts are performed. Under the current assumptions, an existinginaccurate (but not completely obsolete) model is used to expeditethe updates. We use techniques from black box testing and machinelearning. We present an implementation of the proposed methodologycalled AMC (for Adaptive Model Checking). We discuss some experimentalresults, comparing various tactics of updating a model whiletrying to perform model checking.     

“That camera adds ten pounds!:” Women's reactions to visual weight-related feedback and the role of trait body checking

In Study 1 women were randomly assigned to viewing: (1) no photo of themselves, (2) an accurate, full-body photo, (3) a photo modified to make them appear thinner than usual, or (4) a photo modified to make them appear heavier than usual. Measures of mood, state self-esteem, and body dissatisfaction were completed. There were no main effects of photo condition; participants were generally poor at perceiving weight change. The heavier that participants thought they looked in their photo as compared to usual, the worse their appearance self-esteem and body dissatisfaction. Study 2 replicated these results and found that participants with higher levels of trait body checking were more likely to report that they looked heavier than usual in the photo. Study 3 replicated these results and found that the correlation between body parts checking and how participants thought they looked in the photo held true even after controlling for appearance investment.     

Advances in the Cognitive Behavioural Treatment of Obsessive Compulsive Disorder

The aim of this paper is to highlight key advances in the cognitive-behavioural treatment of obsessive compulsive disorder over the course of Professor Lars Göran Öst's illustrious career. The paper will focus on three specific areas of interest: the treatment of obsessions, compulsive checking, and the fear of contamination. It will also highlight recent advances concerning the broader need to ensure that treatment is acceptable. An increase in acceptability could result in improvements in completion rates so that more patients benefit from the recent improvements in the science and therapy for this disabling disorder.     

Deficits in set-shifting ability in nonclinical compulsive checkers

Recent studies suggest deficits in set-shifting ability in patients with obsessive-compulsive disorder (OCD) as measured by tasks such as the Wisconsin Card Sorting Test (WCST; Berg, 1948). The present study examined the extent to which these deficits were demonstrated by nonclinical subjects selected on the basis of their checking scores on the Maudsley Obsessional-Compulsive Inventory. A multivariate analysis revealed that frequent checkers performed significantly worse on the WCST than noncheckers, making more total errors and more perseverative errors and requiring more time to complete the test. A follow-up analysis on a subset of the original sample found similar performance deficits in checkers. While the poorer performance of checkers could be statistically accounted for by anxiety during the first administration of the WCST, anxiety could not explain the relationship between checking status and WCST performance at follow-up. Therefore, there does appear to be some relationship between checking status and WCST performance beyond what can be explained by affective variables.     

Automatic verification of multi-agent systems by model checking via ordered binary decision diagrams

We present a methodology for the verification of multi-agent systems, whose properties are specified by means of a modal logic that includes a temporal, an epistemic, and a modal operator to reason about correct behaviour of agents. The verification technique relies on model checking via ordered binary decision diagrams. We present an implementation and report on experimental results for two scenarios: the bit transmission problem with faults and the protocol of the dining cryptographers.     

An experimental analysis of body checking

The relationship between repeated body checking and its impact on body size estimation and body dissatisfaction is of interest for two reasons. First, it has importance in theoretical accounts of the maintenance of eating disorders and, second, body checking is targeted in cognitive-behavioural treatment. The aim of this study was to determine the impact of manipulating body checking on body size estimation and body dissatisfaction. Sixty women were randomly assigned either to repeatedly scrutinize their bodies in a critical way in the mirror ("high body checking") or to refrain from body checking but to examine the whole of their bodies in a neutral way ("low body checking"). Body dissatisfaction, feelings of fatness and the strength of a particular self-critical thought increased immediately after the manipulation among those in the high body checking condition. Feelings of fatness decreased among those in the low body checking condition. These changes were short-lived. The manipulation did not effect estimations of body size or the discrepancy between estimations of body size and desired body size. The implications of these findings for understanding the influence of body checking on the maintenance of body dissatisfaction are considered.     

Deteriorating memory confidence, responsibility perceptions and repeated checking: comparisons in OCD and control samples

Repeated checking has been repeatedly associated with memory distrust. We sought to extend previous research using a computer-based checking task by incorporating a group of 15 individuals with OCD, and examining the effect of increased perceived responsibility. Participants were asked to repeatedly check a virtual stovetop, with half the participants also placed under a condition of high-perceived responsibility. Our observations replicated previous research showing that the act of repeatedly checking leads to reductions in memory vividness, detail and confidence, without accompanying reductions in memory accuracy. Furthermore, while a sense of increased personal responsibility had little effect on a student control sample, it led to a significant further deterioration in memory confidence in individuals with OCD. These results suggest that in people with OCD, normal reductions in memory confidence over repeated trials are exacerbated and intensified by inflated responsibility perceptions.