Deduction chains for common knowledge

Deduction chains represent a syntactic and in a certain sense constructive method for proving completeness of a formal system. Given a formula , the deduction chains of are built up by systematically decomposing into its subformulae. In the case where is a valid formula, the decomposition yields a (usually cut-free) proof of . If is not valid, the decomposition produces a countermodel for . In the current paper, we extend this technique to a semiformal system for the Logic of Common Knowledge. The presence of fixed point constructs in this logic leads to potentially infinite-length deduction chains of a non-valid formula, in which case fairness of decomposition requires special attention. An adequate order of decomposition also plays an important role in the reconstruction of the proof of a valid formula from the set of its deduction chains.     

On the consistency problem for the calculus

In this paper, we further investigate the consistency problem for the qualitative temporal calculus introduced by Pujari et al. [A.K. Pujari, G.V. Kumari, A. Sattar, INDU: An interval and duration network, in: Australian Joint Conference on Artificial Intelligence, 1999, pp. 291–303]. We prove the intractability of the consistency problem for the subset of pre-convex relations, and the tractability of strongly pre-convex relations. Furthermore, we also define another interesting set of relations for which the consistency problem can be decided by the -closure method, a method similar to the usual path-consistency method. Finally, we prove that the -closure method is also complete for the set of atomic relations of implying that the intervals have the same duration.     

Hybrids of the -translation for

In [W. Burr, Functional interpretation of Aczel's constructive set theory, Annals of Pure and Applied Logic 104 (2000) 31–73] Wolfgang Burr presents a functional interpretation of constructive set theory in all finite types, , in a theory of constructive set functionals. is a subtheory of , containing bounded quantifiers only. His interpretation theorem reduces the consistency problem of (and certain extensions thereof) to the consistency problem of .We want to study admissible rules in , i.e. rules under which is closed. To do so, we study a Troelstra-style q-hybrid of, in fact, a modification ^× of Burr's translation. We introduce this modification in order to close a minor gap in Burr's proof of the functional interpretation of the schema of (Strong Collection).First of all, but surely after a short introduction, we analyse the less complex translation of modified realisation ^mr and its hybrids ^mq and ^mrt.     

Do Conditional Hypotheses Target Rare Events?

When testing hypotheses, rare or unexpected observations are normatively more informative than common observations, and recent studies have shown that participants' behavior reflects this principle. Research has also shown that, when asked to test conditional hypotheses (“If X, then Y”) that are abstract or unfamiliar, participants overwhelmingly consider a supporting observation mentioned in the hypothesis (X&Y) to be more informative than a supporting observation not mentioned (XY). These two empirical findings would mesh well if conditional hypotheses tend to be phrased in terms of rare, rather than common, events. Six experiments are reported indicating that people do have a tendency—often a very strong one—to phrase conditional hypotheses in terms of rare events. Thus, observations mentioned in conditional hypotheses might generally be considered highly informative because they usually are highly informative.     

Essential unifiers

A substitution δ is less general than a substitution σ if there exists λ such that δ=σλ, which induces a notion of generality in the algebra of substitutions. We propose to look at this well known concept of generality again, and to impose a new quasi ordering on substitutions as a natural result of a stronger notion of the composition of substitutions. This new generality ordering has important consequences for the theory of E-unification (unification in equational theories) and changes the basic notion of the most general unifiers, now called essential unifiers, as well as the unification hierarchy. In particular we show that for idempotent Semigroups (associativity and idempotency), also known as Bands, the set of essential unifiers always exists and is finite.     

Sources of variability in working memory in early childhood: A consideration of age, temperament, language, and brain electrical activity

This study investigated age-related differences in working memory and inhibitory control (WMIC) in -, 4-, and -year-olds and how these differences were associated with differences in regulatory aspects of temperament, language comprehension, and brain electrical activity. A series of cognitive control tasks was administered to measure WMIC ability, including the Stroop-like day–night and the yes–no tasks. Baseline and task electroencephalographic data were collected. The Children's Behavior Questionnaire was used to assess caregiver perceptions of temperament with a particular interest in the effortful control and surgency factors, and language comprehension was measured with the Peabody-Picture Vocabulary Test-III. The results of this study demonstrated differential temperament-cognition relations for the three age groups, as positive associations were found between WMIC and effortful control for the - and 4-year-olds and negative associations were found between WMIC and surgency for the -year-olds. An increasingly robust relation between WMIC and language comprehension was demonstrated across the three age groups, as well as differential patterns of task-related brain electrical activity.     

On the provenance of judgments of conditional probability

In standard treatments of probability, is defined as the ratio of to , provided that . This account of conditional probability suggests a psychological question, namely, whether estimates of arise in the mind via implicit calculation of . We tested this hypothesis (Experiment 1) by presenting brief visual scenes composed of forms, and collecting estimates of relevant probabilities. Direct estimates of conditional probability were not well predicted by . Direct estimates were also closer to the objective probabilities defined by the stimuli, compared to estimates computed from the foregoing ratio. The hypothesis that arises from the ratio fared better (Experiment 2). In a third experiment, the same hypotheses were evaluated in the context of subjective estimates of the chance of future events.     

A kinematic and dynamic comparison of surface and underwater displacement in high level monofin swimming

Fin swimming performance can be divided into underwater and surface water races. World records are about 10% faster for underwater swimming vs. surface swimming, but little is known about the advantage of underwater swimming for monofin swimming. Some authors reported that the air–water interface influences the kinematics and leads to a narrow vertical amplitude of the fin. On the one hand, surface swimming is expected to affect drag parameters (cross-sectional area (S) and active drag (AD)) when compared to underwater swimming. On the other hand, the surface swimming technique may also affect efficiency (η_F). The aim of this study is therefore to evaluate and compare drag parameters and efficiency during underwater and surface swimming. To this end, 12 international level monofin swimmers were measured during both underwater and surface swimming. Kinematic parameters (both dimensional and non-dimensional), η_F (calculated according to the Elongated-Body Theory), and AD (computed with Velocity Perturbation Method) were calculated for an underwater and a surface fin swimming trial, performed at maximal speed. As expected, results showed significantly lower velocities during surface swimming vs. underwater  = 2.5 m s⁻¹ vs.  = 2.36 m s⁻¹, p < .01). Velocities during underwater and surface swimming were strongly correlated (r = .97, p < .01). Underwater swimming was also associated with higher vertical amplitudes of the fin compared to surface swimming ( = 0.55 m vs. ) = 0.46 m, p < .01). Length-specific amplitudes (A_under/L_b) were in the order of 20% during underwater swimming as for undulating fish, and significantly higher than during surface swimming (A_surf/L_b = 17%, p < .01). Efficiency for surface swimming was about 6% lower than for underwater swimming ( = 0.79 vs.  = 0.74, p < .01). This decrease could be associated with an increase in swimming frequency for surface swimming ( = 2.15 Hz vs.  = 2.08 Hz, p < .01). Active drag during surface swimming was about 7% higher than for underwater swimming ( = 78.9 N vs.  = 84.7 N, p < .01). A significantly smaller cross-sectional area for surface swimming ( = 0.053 m² vs.  = 0.044 m², p < .01) and higher drag coefficient for surface swimming ( = 0.47 vs.  = 0.69, p < .01) were measured. Finally, correlation between cross-sectional area and vertical amplitude of the fin was reported for both underwater and surface swimming. These results suggest that the performance improvement during underwater swimming is not only linked to a wave drag reduction effect but also to a specific swimming technique due to the free surface.     

The phenotypic and genotypic relation between working memory speed and capacity

This study examined the phenotypic and genotypic relationship between working memory speed (WMS) and working memory capacity (WMC) in 12-year-old twins and their siblings (N = 409). To asses WMS all children performed a reaction time task with three memory loads from which a basic mental speed measure and the derived slope were used. WMC was measured with two subtests of the WISC-R, namely Arithmetic and Digit Span. The phenotypic correlations among the WMS and WMC indices were around − 0.30. Heritabilities for all variables ranged from 43% to 56%. Structural equating modelling revealed that a model with two genetic factors, representing WMS and WMC, which were correlated (− 0.54) fitted the data best, indicating that WMS and WMC are partly mediated by the same set of genes and partly by separate sets of genes. When general IQ was simultaneously analysed with the data the correlation between the genetic factors for WMS and WMC decreased (− 0.25), but was still significant. This means that  50% of the genetic correlation between WMS and WMC is explained by IQ.     

Using information criteria to determine the number of regimes in threshold autoregressive models

Threshold autoregressive models can be used to study processes that are characterized by recurrent switches between two or more regimes, where switching is triggered by a manifest threshold variable. In this paper the performance of diverse information criteria for selecting the number of regimes in small to moderate sample sizes (i.e., n=50,100,200) is investigated. In addition it is investigated whether these information criteria can be used to determine whether the residual variances are identical across the regimes. It is concluded that for small sample sizes should be preferred, while for larger sample sizes either BIC or should be considered: The latter is the only information criterion that includes a penalty for the unknown threshold parameters.     

Personality traits and body mass index: Modifiers and mechanisms

Objective: To identify how demographic factors (sex, age, ethnicity) modify the association between personality traits and body mass index (BMI) and to test the extent that diet and physical activity account for the personality-BMI relations.

Design: Cross-sectional study with a diverse sample (N = 5150, 50% female, 19% African American, 15% Hispanic). Participants completed a measure of the five major dimensions of personality and reported on their physical activity, diet and food intake behaviour, and height and weight.

Main Outcome Measures: BMI and obesity (BMI ≥ 30).

Results: High Neuroticism was associated with higher BMI and risk for obesity, whereas Conscientiousness and, to a lesser extent, Extraversion and Openness were protective. These associations were generally stronger among women and older participants; there was less evidence for ethnicity as a moderator. Personality had similar relations with the behavioural factors, and physical activity, diet and regular meal rhythms accounted for approximately 50% of the association between Neuroticism and Conscientiousness and BMI.

Conclusion: This study supports the links between personality traits and BMI and suggests that physical activity, more than diet, is a key factor in these associations.     

Sense of coherence,hope, and home demolition are differentially associated with anger and anxiety among Bedouin Arab adolescents in recognized and unrecognized villages

Background and objectives: This research investigated how coping resources explain emotional reactions of anger and anxiety, in the context of threat of house demolition, among adolescents in three groups: Adolescents living in a recognized village with no demolition, adolescents living in an unrecognized village (by the Israeli government as legal) with no demolition, and adolescents living in an unrecognized village with demolition. The framework of this research is based on Antonovsky’s salutogenic theory, which suggests examining ability to cope with stressful situations.

Design: Multi-group cross-sectional study.

Methods: The study was carried out during 2010–2011 and included 910 participants, of whom 411 adolescents lived in unrecognized villages where 193 of them experienced home demolition. Participants filled out a questionnaire including demographics, coping resources and emotional reactions.

Results: Findings showed that stress reactions were the highest among adolescents from unrecognized villages with demolition. Personal sense of coherence (SOC) was related to fewer emotional reactions among the adolescents from recognized villages; among adolescents from unrecognized villages, especially adolescents living in an unrecognized village with demolition, a stronger SOC was linked to stronger emotional reactions.

Conclusions: These findings have important implications for understanding the role of coping among youth from different cultural groups.     

Social networks and web minorities

The conception of appropriate models of information retrieval is a crucial step for the actual growth and development of the web. In addition to traditional information retrieval techniques, nowadays search engines have adopted methods for taking into account the social network deriving from the pattern of interconnections. Using different arguments, it has been shown that this is very effective in practice. In this paper we subscribe that point of view, but state also that social networks based ranking schemes operating on the whole web, like Google’s , prevent small communities to become visible on the Web, regardless of the quality of the information. Hence, we strongly advocate the development of new cognitive models of the whole process of information retrieval which are capable of facing this problem. We give a picture of distributed architectures which incorporates topic-based intelligent agents and personal agents for capturing the user’s profile.     

On becoming neutral: effects of experimental neutralizing reconsidered

Behaviour Research and Therapy 34 (1996) 889–898 found that writing out a negative thought produced anxiety and an urge to neutralize the thought, that instructing participants to neutralize the thought reduced anxiety/neutralization urge in the short run (i.e. within 2 min), but that in the control group 20 min without instruction was attended by the same reduction in anxiety/urge to neutralize (“natural decay”). The observations were made with pariticipants who scored high on “thought action fusion” and the experiment was set up as exerimental model of obsessions. We repeated the study with participants that were not selected on thought action fusion. All the findings reported by Behaviour Research and Therapy 34 (1996) 889–898 were replicated. Correlational analysis indicated that the strength of the effect was not related to scores on scales measuring “thought action fusion”. Behaviour Research and Therapy 34 (1996) 889–898 did not assess whether non-neutralizing was followed by immediate reductions in distress. We did assess this and found that the larger part of the immediate reduction of distress after neutralization also occurs when no neutralization instruction is given. The effects of neutralization instructions in the present type of experiment are considerably less powerful than suggested earlier.     

Skull size and intelligence, and King Robert Bruce's IQ

An estimate of someone's IQ is a potentially informative personal datum. This study examines the association between external skull measurements and IQ scores, and uses the resulting regression equation to provide an estimate of the IQ of King Robert I of Scotland (Robert Bruce, 1274–1329). Participants were 48 relatively healthy Caucasian men (age 71–76 years) resident in Scotland. Using magnetic resonance imaging data, intracranial volume estimated from external skull length and width correlated greater than .5 (p < .001) with measured intracranial area, which correlates very highly with brain volume. IQ scores estimated from the National Adult Reading Test (NART) correlated .56 (p < .001) with measured intracranial area, and .49 (p < .01) with estimated intracranial volume based on external skull width and length. The partial correlation coefficient of this latter association was .25 (p = .09) after adjustment for measured intracranial area. Thus, actual intracranial area accounts for about 74% of the variance shared by NART and estimated intracranial volume. A cast of the skull of Robert Bruce was measured and its intracranial volume estimated. A regression equation between IQ and estimated intracranial volume, based on data from the 48 subjects, estimated the IQ of Robert Bruce at about 128 (95% confidence interval 106 to  130), i.e. almost two standard deviations above the mean. NART scores show a ceiling effect, so this estimated IQ might be an underestimate. Robert Bruce's estimated high IQ is congruent with his military, political and other intellectual achievements.     

Effects of Curriculum-Based Monitoring on Classroom Instruction and Math Achievement

In recent years, concerns about the math achievement of U.S. students have been highlighted in the popular press, journal articles, major conference presentations, and official U.S. Department of Education (1998) reports. School personnel have responded to the issue of low math achievement by a) writing or rewriting standards, b) “ratcheting up” current standards, c) building accountability systems that include all students, d) developing programmatic interventions, e) extending the school year, and f) implementing effective instructional management systems. Research on teaching has linked instructional environment and achievement. Thus, this study was designed to determine whether the implementation of an instructional management system served to improve student math achievement and the classroom instructional environment. In addition, the study examined the extent to which adding a curriculum-based monitoring system to an ongoing math curriculum would result in positive changes in the classroom instructional environment and in achievement.