A Neural Theory of Visual Search: Recursive Attention to Segmentations and Surfaces

A neural theory is proposed in which visual search is accomplished by perceptual grouping and segregation, which occurs simultaneous across the visual field, and object recognition, which is restricted to a selected region of the field. The theory offers an alternative hypothesis to recently developed variations on Feature Integration Theory (Treisman, and Sato, 1991) and Guided Search Model (Wolfe, Cave, and Franzel, 1989). A neural architecture and search algorithm is specified that quantitatively explains a wide range of psychophysical search data (Wolfe, Cave, and Franzel, 1989; Cohen, and lvry, 1991; Mordkoff, Yantis, and Egeth, 1990; Treisman, and Sato, 1991).

A Neural Theory of Attentive Visual Search: Interactions of Boundary, Surface, Spatial, and Object Representations

Visual search data are given a unified quantitative explanation by a model of how spatial maps in the parietal cortex and object recognition categories in the inferotemporal cortex deploy attentional resources as they reciprocally interact with visual representations in the prestriate cortex. The model visual representations arc organized into multiple boundary and surface representations. Visual search in the model is initiated by organizing multiple items that lie within a given boundary or surface representation into a candidate search grouping. These items arc compared with object recognition categories to test for matches or mismatches. Mismatches can trigger deeper searches and recursive selection of new groupings until a target object io identified. This search model is algorithmically specified to quantitatively simulate search data using a single set of parameters, as well as to qualitatively explain a still larger data base, including data of Aks and Enns (1992), Bravo and Blake (1990), Chellazzi, Miller, Duncan, and Desimone (1993), Egeth, Viri, and Garbart (1984), Cohen and Ivry (1991), Enno and Rensink (1990), He and Nakayarna (1992), Humphreys, Quinlan, and Riddoch (1989), Mordkoff, Yantis, and Egeth (1990), Nakayama and Silverman (1986), Treisman and Gelade (1980), Treisman and Sato (1990), Wolfe, Cave, and Franzel (1989), and Wolfe and Friedman-Hill (1992). The model hereby provides an alternative to recent variations on the Feature Integration and Guided Search models, and grounds the analysis of visual search in neural models of preattentive vision, attentive object learning and categorization, and attentive spatial localization and orientation.

In search of Cork's collecting traditions: from Kilcrea's Library to the Boole Library of today

The objective of this essay is not a description of the presently unresearched, unstated and unquantified tradition of collectors, collecting and collectables in Cork; it is rather one of signposting what survives in terms of influences which coalesced into what became the bibliographical and museological resources of the Queen's College and ultimately University College, Cork (UCC).

Identifying sources of global contention in constraint satisfaction search

Much work has been done on learning from failure in search to boost solving of combinatorial problems, such as clause-learning and clause-weighting in boolean satisfiability (SAT), nogood and explanation-based learning, and constraint weighting in constraint satisfaction problems (CSPs). Many of the top solvers in SAT use clause learning to good effect. A similar approach (nogood learning) has not had as large an impact in CSPs. Constraint weighting is a less fine-grained approach where the information learnt gives an approximation as to which variables may be the sources of greatest contention. In this work we present two methods for learning from search using restarts, in order to identify these critical variables prior to solving. Both methods are based on the conflict-directed heuristic (weighted-degree heuristic) introduced by Boussemart et al. and are aimed at producing a better-informed version of the heuristic by gathering information through restarting and probing of the search space prior to solving, while minimizing the overhead of these restarts. We further examine the impact of different sampling strategies and different measurements of contention, and assess different restarting strategies for the heuristic. Finally, two applications for constraint weighting are considered in detail: dynamic constraint satisfaction problems and unary resource scheduling problems.

The endless search for SA: spiritual ideology in Hindustāni music

This dissertation centres on philosophical attitudes presented by North Indian classical musicians in relation to the concept and experience of rāga improvisation. In Hindustāni music, there is a dynamic tension ideology and pragmatism, devotion and entertainment, fixity and improvisational freedom, and cognition and visceral experience. On one hand, rāga is an embodied methodological template for the creation of music. On the other hand, rāga improvisation is conceptualised as a path to metaphysical experience and as an evocation of an ineffable divine presence. A masterful rendition of rāga is both a re-enactment of a systematic prescribed formula and a spontaneous flow of consciousness. This study presents these apparent dichotomies to highlight ideological concerns, while simultaneously contextualising philosophical idealism in relation to pragmatic realities. A central paradigm is the manner in which pragmatic concerns are elevated in status and given spiritual significance. The dissertation begins with a view into historical and religious context. The discussion continues with a speculative investigation positing co-relations between Hindustāni music and central tenets of Indian philosophy, considering how rāga improvisation may manifest as a philosophy of sound. The study then explores the concept of rāga, a modal and conceptual construct that forms the heart of Indian classical music. The final three sections ground the subject of spiritual ideology within the life experience of Hindustāni musicians: ‘Transmission’ looks at the learning and enculturation process, which encapsulates values intrinsic to the ethos of Hindustāni music culture. ‘Practice’ explores the discipline, science and experience of musical practice, revealing core ideological concerns connecting spirituality to musical experience; and ‘Performance’ examines the live presentation of rāga improvisation, and the relationship between music as ‘entertainment’ and music as ‘devotion’. Both ethnographic and musicological, this research is the culmination of various fieldtrips to India, extensive interviews with Hindustāni musicians, fifteen year’s sitār training, and the study of relevant musicological and philosophical texts.

Man's search for meaning: The case of Legos

We investigate how perceived meaning influences labor supply. In a laboratory setting, we manipulate the perceived meaning of simple, repetitive tasks and find a strong influence on subjects' labor supply. Despite the fact that the wage and the task are identical across the conditions in each experiment, subjects in the less meaningful conditions exhibit reservation wages that are consistently much higher than the subjects in the more meaningful conditions. The result replicates across different types of tasks. Moreover, in the more meaningful conditions, subjects' productivity influences labor supply more strongly. © 2008 Elsevier B.V. All rights reserved.

TRANSCENDING FACH: A SEARCH FOR IDENTITY INSIDE AND OUT OF MEZZO-SOPRANO REPERTOIRE

The German Fach system is a tool to classify voices in classical singing. This dissertation comprises three different programs that reflect my search for identity as a mezzo-soprano and my desire to transcend the limitations of Fach. The three programs, all presented at The Clarice Performing Arts Center, contain repertoire written for male and female voices thus allowing me to explore areas outside of the mezzo-soprano Fach, gain a better understanding of the Fach system and guide me as I strive to become a more mature performer. In my first program, I sang the role of Sesto, a role that was composed originally for a castrate, in the opera La Clemenza di Tito by W.A. Mozart. The Maryland Opera Studio production took place April 30, May 2,4&6,2003. Performing this gender-bending role provided an experience of physical behavior from the male view point along with the demands of coloratura singing. Program two (November 30,2004) contained the song cycle Dichterliebe by Robert Schumann and songs by Ludwig van Beethoven, Franz Schubert and Felix Mendelssohn, which are usually sung by male voices. This program experimented with extended range, tessitura and a gender-bending performance in the art song arena. 8 In program three (April 21 &23,2005), I sang the contralto role of Cornelia from Giulio Cesare in Egitto by George Frederic Handel. The role of Cornelia is psychologically complex, expressing emotions such as love, melancholy, rage, malice, joy and fear. To convey these emotions a voice needs warmth and darkness of quality. Although the range is close to that of the mezzo-soprano, Handel wrote Cornelia for contralto voice because he wanted a dark timbre and this role allowed me to develop my lower register and manage suitable ornamentations. The programs are documented in a digital format available on compact disc and are accompanied by the oral presentation at the defense of this dissertation.

Rare targets are rarely missed in correctable search.

Failing to find a tumor in an x-ray scan or a gun in an airport baggage screening can have dire consequences, making it fundamentally important to elucidate the mechanisms that hinder performance in such visual searches. Recent laboratory work has indicated that low target prevalence can lead to disturbingly high miss rates in visual search. Here, however, we demonstrate that misses in low-prevalence searches can be readily abated. When targets are rarely present, observers adapt by responding more quickly, and miss rates are high. Critically, though, these misses are often due to response-execution errors, not perceptual or identification errors: Observers know a target was present, but just respond too quickly. When provided an opportunity to correct their last response, observers can catch their mistakes. Thus, low target prevalence may not be a generalizable cause of high miss rates in visual search.

Comprehensive search for new phases and compounds in binary alloy systems based on platinum-group metals, using a computational first-principles approach

We report a comprehensive study of the binary systems of the platinum-group metals with the transition metals, using high-throughput first-principles calculations. These computations predict stability of new compounds in 28 binary systems where no compounds have been reported in the literature experimentally and a few dozen of as-yet unreported compounds in additional systems. Our calculations also identify stable structures at compound compositions that have been previously reported without detailed structural data and indicate that some experimentally reported compounds may actually be unstable at low temperatures. With these results, we construct enhanced structure maps for the binary alloys of platinum-group metals. These maps are much more complete, systematic, and predictive than those based on empirical results alone.

BAYESIAN MODEL SEARCH AND MULTILEVEL INFERENCE FOR SNP ASSOCIATION STUDIES.

Technological advances in genotyping have given rise to hypothesis-based association studies of increasing scope. As a result, the scientific hypotheses addressed by these studies have become more complex and more difficult to address using existing analytic methodologies. Obstacles to analysis include inference in the face of multiple comparisons, complications arising from correlations among the SNPs (single nucleotide polymorphisms), choice of their genetic parametrization and missing data. In this paper we present an efficient Bayesian model search strategy that searches over the space of genetic markers and their genetic parametrization. The resulting method for Multilevel Inference of SNP Associations, MISA, allows computation of multilevel posterior probabilities and Bayes factors at the global, gene and SNP level, with the prior distribution on SNP inclusion in the model providing an intrinsic multiplicity correction. We use simulated data sets to characterize MISA's statistical power, and show that MISA has higher power to detect association than standard procedures. Using data from the North Carolina Ovarian Cancer Study (NCOCS), MISA identifies variants that were not identified by standard methods and have been externally "validated" in independent studies. We examine sensitivity of the NCOCS results to prior choice and method for imputing missing data. MISA is available in an R package on CRAN.

Postoperative statin use and risk of biochemical recurrence following radical prostatectomy: results from the Shared Equal Access Regional Cancer Hospital (SEARCH) database.

OBJECTIVE: To investigate the effect of statin use after radical prostatectomy (RP) on biochemical recurrence (BCR) in patients with prostate cancer who never received statins before RP. PATIENTS AND METHODS: We conducted a retrospective analysis of 1146 RP patients within the Shared Equal Access Regional Cancer Hospital (SEARCH) database. Multivariable Cox proportional hazards analyses were used to examine differences in risk of BCR between post-RP statin users vs nonusers. To account for varying start dates and duration of statin use during follow-up, post-RP statin use was treated as a time-dependent variable. In a secondary analysis, models were stratified by race to examine the association of post-RP statin use with BCR among black and non-black men. RESULTS: After adjusting for clinical and pathological characteristics, post-RP statin use was significantly associated with 36% reduced risk of BCR (hazard ratio [HR] 0.64, 95% confidence interval [CI] 0.47-0.87; P = 0.004). Post-RP statin use remained associated with reduced risk of BCR after adjusting for preoperative serum cholesterol levels. In secondary analysis, after stratification by race, this protective association was significant in non-black (HR 0.49, 95% CI 0.32-0.75; P = 0.001) but not black men (HR 0.82, 95% CI 0.53-1.28; P = 0.384). CONCLUSION: In this retrospective cohort of men undergoing RP, post-RP statin use was significantly associated with reduced risk of BCR. Whether the association between post-RP statin use and BCR differs by race requires further study. Given these findings, coupled with other studies suggesting that statins may reduce risk of advanced prostate cancer, randomised controlled trials are warranted to formally test the hypothesis that statins slow prostate cancer progression.

IN SEARCH OF THE DIVINE: SPIRITUALITY AND PRAYER IN DIVERSE VIOLIN REPERTOIRE FROM BIBER TO IVES

Composers from all eras and of all ethnicities explore spirituality and prayer by using one or a combination of the following ideas: having a spiritual concept in mind when composing certain pieces, quoting hymns, being influenced by their own personal beliefs, or portraying spiritual figures and ideas in their works. Some musical works are inspired by spirituality; others, as in the case of Bloch's Nigun, even serve as prayers themselves. These recitals gave me the opportunity to approach a wide variety of musical styles while discovering my own mode for expression. The unaccompanied violin works throughout this project trace a distinct lineage from the baroque to the twentieth century. Biber's appendix to the Rosary Sonatas, the Passacaglia for solo violin, is a crucial predecessor to Bach's monumental Chaconne. Eugene Ysaye was inspired to write the Six Sonatas, Op. 27 after he attended a performance of Bach's Sonatas and Partitas given by Josef Szigeti. Ysaye's second solo sonata blatantly quotes Bach's Partita No.3 in E major throughout the first movement. Every movement also contains quotations from and variations on the plainchant Dies Irae. Although each of the solo violin works presented in this project may be viewed as virtuosic concert pieces, each piece allows the performer to transcend the technical hurdles-and perhaps even utilize them-to serve a higher, artistic and spiritual purpose while alone on the concert stage. Each of the sonata works in this project requires a close, equal collaboration between violinist and pianist, rather than displaying the violinist as soloist.

Improvement in visual search with practice: mapping learning-related changes in neurocognitive stages of processing.

Practice can improve performance on visual search tasks; the neural mechanisms underlying such improvements, however, are not clear. Response time typically shortens with practice, but which components of the stimulus-response processing chain facilitate this behavioral change? Improved search performance could result from enhancements in various cognitive processing stages, including (1) sensory processing, (2) attentional allocation, (3) target discrimination, (4) motor-response preparation, and/or (5) response execution. We measured event-related potentials (ERPs) as human participants completed a five-day visual-search protocol in which they reported the orientation of a color popout target within an array of ellipses. We assessed changes in behavioral performance and in ERP components associated with various stages of processing. After practice, response time decreased in all participants (while accuracy remained consistent), and electrophysiological measures revealed modulation of several ERP components. First, amplitudes of the early sensory-evoked N1 component at 150 ms increased bilaterally, indicating enhanced visual sensory processing of the array. Second, the negative-polarity posterior-contralateral component (N2pc, 170-250 ms) was earlier and larger, demonstrating enhanced attentional orienting. Third, the amplitude of the sustained posterior contralateral negativity component (SPCN, 300-400 ms) decreased, indicating facilitated target discrimination. Finally, faster motor-response preparation and execution were observed after practice, as indicated by latency changes in both the stimulus-locked and response-locked lateralized readiness potentials (LRPs). These electrophysiological results delineate the functional plasticity in key mechanisms underlying visual search with high temporal resolution and illustrate how practice influences various cognitive and neural processing stages leading to enhanced behavioral performance.

Multi-touch and keyboard/mouse devices comparison in an information search task: influence on cognitive load and task engagement

Nowadays multi-touch devices (MTD) can be found in all kind of contexts. In the learning context, MTD availability leads many teachers to use them in their class room, to support the use of the devices by students, or to assume that it will enhance the learning processes. Despite the raising interest for MTD, few researches studying the impact in term of performance or the suitability of the technology for the learning context exist. However, even if the use of touch-sensitive screens rather than a mouse and keyboard seems to be the easiest and fastest way to realize common learning tasks (as for instance web surfing behaviour), we notice that the use of MTD may lead to a less favourable outcome. The complexity to generate an accurate fingers gesture and the split attention it requires (multi-tasking effect) make the use of gestures to interact with a touch-sensitive screen more difficult compared to the traditional laptop use. More precisely, it is hypothesized that efficacy and efficiency decreases, as well as the available cognitive resources making the users’ task engagement more difficult. Furthermore, the presented study takes into account the moderator effect of previous experiences with MTD. Two key factors of technology adoption theories were included in the study: familiarity and self-efficacy with the technology.Sixty university students, invited to a usability lab, are asked to perform information search tasks on an online encyclopaedia. The different tasks were created in order to execute the most commonly used mouse actions (e.g. right click, left click, scrolling, zooming, key words encoding…). Two different conditions were created: (1) MTD use and (2) laptop use (with keyboard and mouse). The cognitive load, self-efficacy, familiarity and task engagement scales were adapted to the MTD context. Furthermore, the eye-tracking measurement would offer additional information about user behaviours and their cognitive load.Our study aims to clarify some important aspects towards the usage of MTD and the added value compared to a laptop in a student learning context. More precisely, the outcomes will enhance the suitability of MTD with the processes at stakes, the role of previous knowledge in the adoption process, as well as some interesting insights into the user experience with such devices.