Illusory causal connections and their effect on subjective probability

Our world is filled with statistical information: from dice rolls to lotteries, we often act based on our impressions of probability. Yet the human mind is not wired to reason about truly probabilistic events, often imposing structure on data or events where no such structure exists (as in ‘illusory correlations’). Here, we consider a case study in intuitive statistics: disjunctive events. For example, participants are asked to imagine a button that, when pressed, has a 1 in 100 chance of yielding a prize. They are told to imagine pressing that button 100 times. Across several paradigms, we show that people overestimate the probability of this disjunctive event — in stark contrast to classic demonstrations where people underestimate such probabilities (e.g., when iteratively selecting marbles from jars with replacement). These results reflect a tendency to view events as causally connected in illusory ways; implications for other domains of reasoning are discussed

Statistical analysis of particulate matter data in Doha, Qatar

Pollution in Doha is measured using passive, active and automatic sampling. In this paper we consider data automatically sampled in which various pollutants were continually collected and analysed every hour. At each station the sample is analysed on-line and in real time and the data is stored within the analyser, or a separate logger so it can be downloaded remotely by a modem. The accuracy produced enables pollution episodes to be analysed in detail and related to traffic flows, meteorology and other variables. Data has been collected hourly over more than 6 years at 3 different locations, with measurements available for various pollutants – for example, ozone, nitrogen oxides, sulphur dioxide, carbon monoxide, THC, methane and particulate matter (PM1.0, PM2.5 and PM10), as well as meteorological data such as humidity, temperature, and wind speed and direction. Despite much care in the data collection process, the resultant data has long stretches of missing values, when the equipment has malfunctioned – often as a result of more extreme conditions. Our analysis is twofold. Firstly, we consider ways to “clean” the data, by imputing missing values, including identified outliers. The second aspect specifically considers prediction of each particulate (PM1.0, PM2.5 and PM10) 24 hours ahead, using current (and previous) pollution and meteorological data. In this case, we use vector autoregressive models, compare with decision trees and propose variable selection criteria which explicitly adapt to missing data. Our results show that the regression tree models, with no variable transformations, perform the best, and that attempts to impute missing values are hampered by non-random missingness

Non-metastatic cutaneous squamous cell carcinoma treated with photodynamic therapy using intravenous mTHPC

INTRODUCTION Photodynamic therapy (PDT) is a method of treating various pathologies. In this retrospective study with prospective intent, a total of 22 patients with T1/T2 N0 cutaneous squamous cell carcinoma (SCC) were treated with intravenous mTHPC (meta-tetrahydroxyphenylchlorin) and surface illumination PDT. Comparisons with the clinical features, rate of recurrence and overall outcome were made. MATERIALS AND METHODS Surface illumination PDT was offered under local anaesthesia. 0.05 mg/kg mTHPC was administered intravenously into the midcubital vein 48 h prior to tissue illumination. A single-channel 652 nm diode laser was used for illumination and light was delivered at 20 J/cm2 per site. Lesion response evaluation was carried out according to Response Evaluation Criteria In Solid Tumors (RECIST). RESULTS Clinical assessment revealed that 16 patients had lesions of <2 cm in size (T1), while the rest were T2. No nodal involvement was identified in any of the patients. None of the patients had a locally recurrent lesion. During the 3-year follow-up, 20/22 patients had complete response (CR) and this was after one round of treatment. Two patients suffered from recurrent disease within 3 years of the follow-up, and they underwent surgical resection. CONCLUSION PDT achieved high efficacy in the treatment of T1N0 cutaneous squamous cell carcinoma with greatly reduced morbidity and disfigurement. The technique is simple, can commonly be carried out in outpatient clinics, and is highly acceptable to patients

Implicit questions shape information preferences

We ask questions about everything from why clocks tick towhy the sky is blue. Although people sometimes preferteleological explanations over mechanistic explanations inresponse to ‘why’ questions, why questions are ambiguous–referring either to a ‘how’ question or a ‘for what purpose’question. In this paper, we examine the relation between theseimplicit questions and explanation preferences. First, we askedwhether people have specific expectations regarding ‘why’questions: How do they interpret these ambiguous cases anddoes this vary across domains? Indeed, people have strong,domain-specific expectations that mirror well-documentedexplanation preferences. People also have preferences aboutwhich specific question they would prefer to have answered. Inother words, ‘why’ questions are ambiguous but not treated assuch — and this has consequences for downstream explanationpreferences. We explore these consequences in light of both thephilosophical and psychological literature on explanation

EXPERIMENTAL INVESTIGATION OF OPEN LOOP MULTI-STAGE IMPEDANCE PUMPING SYSTEM

Impedance pump is a simple valveless pumping mechanism, where an elastic tube is joined to a more rigid one; a periodic asymmetrical pinching on the elastic tube will produce a unidirectional flow. This pumping concept offers a low energy, low noise alternative at both micro and macro scales. This paper describes an experimental investigation of the performance of a two-stage, open loop impedance pump. The results show that, when compared to a single stage open loop impedance pump, the two-stage impedance pump can achieve a significant pressure head and flow rate increment. A pressure head increment of 240 Pa is obtained in the single stage system compared to 480 Pa for the two-stage system. The corresponding flow rates were 5 mL/s and 8 mL/s respectively. This is an indication that impedance pumping system can be scaled up to achieve a variety of pumping assignments

Assessing the Quality of Annotations in Asthma Gene Expression Experiments

Background: The amount of data deposited in the Gene Expression Omnibus (GEO) has expanded significantly. It is important to ensure that these data are properly annotated with clinical data and descriptions of experimental conditions so that they can be useful for future analysis. This study assesses the adequacy of documented asthma markers in GEO. Three objective measures (coverage, consistency and association) were used for evaluation of annotations contained in 17 asthma studies. Results: There were 918 asthma samples with 20,640 annotated markers. Of these markers, only 10,419 had documented values (50% coverage). In one study carefully examined for consistency, there were discrepancies in drug name usage, with brand name and generic name used in different sections to refer to the same drug. Annotated markers showed adequate association with other relevant variables (i.e. the use of medication only when its corresponding disease state was present). Conclusions: There is inadequate variable coverage within GEO and usage of terms lacks consistency. Association between relevant variables, however, was adequate

Movement speed is biased by prior experience

© 2013 The American Physiological Society. This is an Open Access article licensed under the Creative Commons Attribution license CC BY 3.0 https://creativecommons.org/licenses/by/3.0/deed.en_US which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.How does the motor system choose the speed for any given movement? Many current models assume a process that finds the optimal balance between the costs of moving fast and the rewards of achieving the goal. Here, we show that such models also need to take into account a prior representation of preferred movement speed, which can be changed by prolonged practice. In a time-constrained reaching task, human participants made 25-cm reaching movements within 300, 500, 700, or 900 ms. They were then trained for 3 days to execute the movement at either the slowest (900-ms) or fastest (300-ms) speed. When retested on the 4th day, movements executed under all four time constraints were biased toward the speed of the trained movement. In addition, trial-to-trial variation in speed of the trained movement was significantly reduced. These findings are indicative of a use-dependent mechanism that biases the selection of speed. Reduced speed variability was also associated with reduced errors in movement amplitude for the fast training group, which generalized nearly fully to a new movement direction. In contrast, changes in perpendicular error were specific to the trained direction. In sum, our results suggest the existence of a relatively stable but modifiable prior of preferred movement speed that influences the choice of movement speed under a range of task constraints.Peer reviewedFinal Published versio

Isotropic photonic band gap and anisotropic structures in transmission spectra of two-dimensional 5-fold and 8-fold symmetric quasiperiodic photonic crystals

We measured and calculated transmission spectra of two-dimensional quasiperiodic photonic crystals (PCs) based on a 5-fold (Penrose) or 8-fold (octagonal) symmetric quasiperiodic pattern. The photonic crystal consisted of dielectric cylindrical rods in air placed normal to the basal plane on vertices of tiles composing the quasiperiodic pattern. An isotropic photonic band gap (PBG) appeared in the TM mode, where electric fields were parallel to the rods, even when the real part of a dielectric constant of the rod was as small as 2.4. An isotropic PBG-like dip was seen in tiny Penrose and octagonal PCs with only 6 and 9 rods, respectively. These results indicate that local multiple light scattering within the tiny PC plays an important role in the PBG formation. Besides the isotropic PBG, we found dips depending on the incident angle of the light. This is the first report of anisotropic structures clearly observed in transmission spectra of quasiperiodic PCs. Based on rod-number and rod-arrangement dependence, it is thought that the shapes and positions of the anisotropic dips are determined by global multiple light scattering covering the whole system. In contrast to the isotropic PBG due to local light scattering, we could not find any PBGs due to global light scattering even though we studied transmission spectra of a huge Penrose PC with 466 rods.Comment: One tex file for manuscript and 12 PNG files for figures consisting of Fig.1a-d, 2,3, ...

Epithelial tissue thickness improves optical coherence tomography's ability in detecting oral cancer

BACKGROUND OCT is a non-invasive imaging technique that enables the measurement of epithelial thickness and architectural changes, which can help in the diagnosis of pre-cancerous and cancerous lesions. The purpose of the study was to assess whether epithelial tissue thickness improves optical coherence tomography’s ability in detecting oral cancer. PATIENTS AND METHODS Surgically resected oral margins from 60 patients diagnosed with oral squamous cell carcinoma were subjected to OCT. Three OCT measurements (immediate, 1 h and 24 h post-resection) were conducted per resected tissue specimen to look at the effect of saline and formalin on the specimen and its effect on the reproducibility of the OCT. OCT was, then, used to measure the epithelial tissue thickness in cancer-free and cancer-involved margins in eight oral anatomical locations. This data was, then, combined with architectural changes data to calculate the sensitivity and specificity. RESULTS An overall of 189 cancer-free margins and 51 cancer-involved margins had their epithelial thickness measured using OCT and compared to histopathology. With regards to the validity of the OCT and histopathological measurements, epithelial thickness showed good correlation between different readings at all oral sites. With regards to the reproducibility of the OCT measurements, the mean epithelial thickness for all measurements at first (immediate) and second (1 h post-resection – saline preserved) measurements was not significantly different. Underestimation of the epithelial depth in cancer-free margins was 20 μm, while in the cancer-involved margins was 10 μm. Combining data from architectural changes and epithelial thickness, a sensitivity of 92% and a specificity of 94% was achieved. CONCLUSION Oral epithelium measurements using OCT were valid compared to those made with gold standard pathology. Measurements made using OCT was also reproducible with minor underestimation. Epithelial thickness, combined with architectural changes, led to high accuracy in differentiating between cancer-free and cancer-involved margins