Modelling dynamic decision making with the ACT-R cognitive architecture

This paper describes a model of dynamic decision making in the Dynamic Stocks and Flows (DSF) task, developed using the ACT-R cognitive architecture. This task is a simple simulation of a water tank in which the water level must be kept constant whilst the inflow and outflow changes at varying rates. The basic functions of the model are based around three steps. Firstly, the model predicts the water level in the next cycle by adding the current water level to the predicted net inflow of water. Secondly, based on this projection, the net outflow of the water is adjusted to bring the water level back to the target. Thirdly, the predicted net inflow of water is adjusted to improve its accuracy in the future. If the prediction has overestimated net inflow then it is reduced, if it has underestimated net inflow it is increased. The model was entered into a model comparison competition-the Dynamic Stocks and Flows Challenge-to model human performance on four conditions of the DSF task and then subject the model to testing on five unseen transfer conditions. The model reproduced the main features of the development data reasonably well but did not reproduce human performance well under the transfer conditions. This suggests that the principles underlying human performance across the different conditions differ considerably despite their apparent similarity. Further lessons for the future development of our model and model comparison challenges are considered

User perceptions of sound quality: implications for the design and use of audio-based mobile applications

This study sought to investigate the effect that contextual cues (in particular, device type and content type) have on the perception of sound quality. A sample of 49 participants were tested on different mobile devices sizes (small – iPhone, medium – iPad Mini, and large – iPad) which had identical sound output characteristics within in different usage contexts (generic content vs. musical training app contexts). Results showed that the users’ perception of generic sound types was affected by device type, with iPhones appearing to have better sound quality compared to larger devices. On the other hand, within application contexts, the application type seemed to affect user perceptions more, with the rhythm training application rating poorer on sound quality, picture quality, and likelihood of future use as compared to the pitch training application (although this may be due to the perceived increased difficulty). Together, these findings demonstrate the influence of device and content cues (when actual physical qualities are controlled) on user sound perception. Interestingly, differences in perceived sound quality was not accompanied by an overriding preference for that device as compared to other devices. Instead, considerations such as ease of use seemed to drive considerations for uptake of applications

The relationship between dietary restraint and deficits in reasoning about causes of obesity.

Objective: Increased levels of dietary restraint are associated with deficits on many cognitive tasks. Less is known about how individual differences in restraint influences complex cognition such as reasoning which is the focus of this research.Design: Two experimental studies are reported. In study 1, participants (n = 158) completed a causal conditional reasoning task with statements about weight-related and general causal relationships. Study 2 replicated and extended study 1. Participants (n = 108) completed a causal conditional reasoning task focusing on behavioural causes of weight change or general statements.Main outcome measure: Causal conditional reasoning task performance.Results: In study 1, levels of dietary restraint were negatively associated with reasoning abilities for weight-related statements only. Study 2 replicated the negative association between dietary restraint and reasoning finding the effect in both weight-related, and general, causal judgements.Conclusion: The novel findings show that individual differences in dietary restraint have a wider relationship with cognition than previously demonstrated. Results tentatively support theoretical explanations of a reduction in cognitive capacity, rather than differences in belief, explaining reasoning deficits. These findings open an interesting avenue for research and might have implications for effective decision making about personal health behaviours, such as food choice

Methods used for successful follow-up in a large scale national cohort study in Thailand

Background: Ensuring successful follow-up is essential when conducting a prospective cohort study. Most existing literature reviewing methods to ensure a high response rate is based on experience in developed nations. Findings: We report our 4-year follow-up success for a national cohort study examining the health transition underway in Thailand. We began the cohort study in 2005 with a baseline postal questionnaire sent to all 200,000 Thais enrolled as distance learning students at Sukhothai Thammathirat Open University and residing all over Thailand; 87,134 or 44% of the students responded. Subsequently we used University and national media to inform cohort members of study progress. Also, we prepared a health book with study results and health advice which was distributed to all cohort members. After 4 years we repeated the survey and achieved a 71% response rate. In this paper we report the methods used to achieve this response The initial follow-up mail-out generated a response rate of about 48% reflecting the extensive preparatory work between baseline and follow-up. After 4 rounds of telephone contact (more than 100,000 phone calls) and 4 related mail-out rounds progressively over 16 months an overall response rate was achieved of just over 71% (n = 60,774). The total cost was US$4.06/respondent - 19% for printing, 21% for postage, 14% for tape measures (included in mail-out), 18% for data processing 22% for prizes and 6% for telephone. Conclusions: Many of the methods reported as effective for mail questionnaire and cohort response rates held true for Thailand. These included being associated with a university, incentivating cooperation, follow-up contact, providing a second copy of questionnaire where necessary, and assurance of confidentiality. Telephone contact with the cohort and the small prizes given to responders were particularly important in the Thai context as was Thai leadership of the research team

Damages of the tibial post in constrained total knee prostheses in the early postoperative course – a scanning electron microscopic study of polyethylene inlays

<p>Abstract</p> <p>Background</p> <p>Investigation of the risk of fracture of the polyethylene (PE) inlay in constrained total knee prostheses.</p> <p>Methods</p> <p>Three unused and seven polyethylene inlays that had been implanted in a patient's knee for an average of 25.4 months (min 1.1 months, max 50.2 months) were investigated using scanning electron microscopy (SEM). All inlays were of the same type and size (Genesis II constrained, Smith & Nephew). The PE surface at the transition from the plateau to the post was analyzed.</p> <p>Results</p> <p>The unused inlays had fissure-free surfaces. All inlays that had been implanted in a patient's knee already had distinct fissures at the front and backside of the post.</p> <p>Conclusion</p> <p>The fissures of the transition from the plateau to the post indicated a loading-induced irreversible mechanical deformation and possibly cause the fracture of the inlay.</p

The influence of affordances on user preferences for multimedia language learning applications.

This study investigates the influence of sensory and cognitive affordances on the user experience of mobile devices for multimedia language learning applications. A primarily audio-based language learning application – ‘Vowel Trainer’, was chosen against a comparison, text and picture-based language learning application – ‘Learn English for Taxi Drivers’. Impressions of the two applications were assessed on two different devices that have virtually the same interface and identical sound output (when headphones are used), but differ in physical size: the iPhone and the iPad. A mixed design was chosen, with native language as a group factor and device type (iPad vs. iPhone) and language application type (audio vs. video) as within groups factors. Assessments of sensory and cognitive affordances were made, along with measurement of learner preferences of each application. Data from 41 participants (21 native English speakers, 20 non-native English speakers) were analysed, revealing device differences in both audio and visual subjective quality ratings, despite only visual quality being affected by the device's physical limitations. We suggest that sensory affordances (indexed by subjective quality) are not simply a function of physical limitations, but are heavily influenced by context. The implications for developing design guidelines for language learning and other multimedia applications are discussed

Deconfining Phase Transition as a Matrix Model of Renormalized Polyakov Loops

We discuss how to extract renormalized from bare Polyakov loops in SU(N) lattice gauge theories at nonzero temperature in four spacetime dimensions. Single loops in an irreducible representation are multiplicatively renormalized without mixing, through a renormalization constant which depends upon both representation and temperature. The values of renormalized loops in the four lowest representations of SU(3) were measured numerically on small, coarse lattices. We find that in magnitude, condensates for the sextet and octet loops are approximately the square of the triplet loop. This agrees with a large $N$ expansion, where factorization implies that the expectation values of loops in adjoint and higher representations are just powers of fundamental and anti-fundamental loops. For three colors, numerically the corrections to the large $N$ relations are greatest for the sextet loop, $\leq 25$; these represent corrections of $\sim 1/N$ for N=3. The values of the renormalized triplet loop can be described by an SU(3) matrix model, with an effective action dominated by the triplet loop. In several ways, the deconfining phase transition for N=3 appears to be like that in the $N=\infty$ matrix model of Gross and Witten.Comment: 24 pages, 7 figures; v2, 27 pages, 12 figures, extended discussion for clarity, results unchange