A Tablet-Based Assessment of Rhythmic Ability.

The exponential rise in use of mobile consumer electronics has presented a great potential for research to be conducted remotely, with participants numbering several orders of magnitude greater than a typical research paradigm. Here, we attempt to demonstrate the validity and reliability of using a consumer game-engine to create software presented on a mobile tablet to assess sensorimotor synchronization, a proxy of rhythmic ability. Our goal was to ascertain whether previously observed research results can be replicated, rather than assess whether a mobile tablet achieves comparable performance to a desktop computer. To achieve this, younger (aged 18-35 years) and older (aged 60-80 years) adult musicians and non-musicians were recruited to play a custom-designed sensorimotor synchronization assessment on a mobile tablet in a controlled laboratory environment. To assess reliability, participants performed the assessment twice, separated by a week, and an intra-class correlation coefficient (ICC) was calculated. Results supported the validity of this approach to assessing rhythmic abilities by replicating previously observed results. Specifically, musicians performed better than non-musicians, and younger adults performed better than older adults. Participants also performed best when the tempo was in the range of previously-identified preferred tempos, when the stimuli included both audio and visual information, and when synchronizing on-beat compared to off-beat or continuation (self-paced) synchronization. Additionally, high ICC values (>0.75) suggested excellent test-retest reliability. Together, these results support the notion that consumer electronics running software built with a game engine may serve as a valuable resource for remote, mobile-based data collection of rhythmic abilities

Visual illusions: An interesting tool to investigate developmental dyslexia and autism spectrum disorder

A visual illusion refers to a percept that is different in some aspect from the physical stimulus. Illusions are a powerful non-invasive tool for understanding the neurobiology of vision, telling us, indirectly, how the brain processes visual stimuli. There are some neurodevelopmental disorders characterized by visual deficits. Surprisingly, just a few studies investigated illusory perception in clinical populations. Our aim is to review the literature supporting a possible role for visual illusions in helping us understand the visual deficits in developmental dyslexia and autism spectrum disorder. Future studies could develop new tools – based on visual illusions – to identify an early risk for neurodevelopmental disorders

Configuration-specific attentional modulation of flanker target lateral interactions

Elements of a contour are often easier to detect when they possess collinearity, with their local orientations matching the global orientation of the contour. We recently reported attentional modulation of such lateral interactions between a central near-threshold target Gabor patch and flanking high-contrast patches (Freeman et al, 2001 Nature Neuroscience 4 1032-1036). Here, we examined whether such attentional effects reflect specific modulation of mechanisms sensitive to collinear configurations, or instead more general modulation of sensitivity to either the global or local orientation-components of the stimulus. Thresholds for detecting a central Gabor target were measured, while observers also judged the Vernier alignment between one pair of flankers and ignored a second flanker pair (when present). Target contrast-thresholds were facilitated only when attending collinear flankers. There was no facilitation when attending flankers that shared only local orientation with the target, or flankers that fell on a global axis aligned with target orientation but having orthogonal local orientation. Ignored collinear flankers had no effect on target thresholds. These results demonstrate strong and specific attentional modulation of contour-integration mechanisms in early vision sensitive to collinear configurations

Information design of public documents : applying Gestalt principles to improve user understanding

La conception des documents publics joue un rôle important dans la manière dont l'utilisateur perçoit et comprend les informations importantes qu'ils véhiculent. De plus, la conception de tels documents peut avoir un impact important sur l’utilisateur en ce qui concernesa confiance et son processus décisionnel. Les principes de design d’informationpeuvent apporter de précieuses perspectives sur comment les documents publics devraient être conçus pour qu’ils réalisent leurs objectifs. Cependant, le domaine du design d’informationdes documents publics souffre d’un manque important dans l’application de ces principes. D'autre part, les principes perceptuels delaGestalt peuvent expliquer comment les humains organisent des éléments visuels en groupes et comment ils reconnaissent des patrons. Depuis leur introduction au début du XXesiècle, les principes delaGestalt ont servi à améliorer le processus visuo-perceptuel dans différents champs d'application (telles que la peinture, la sculpture, la création graphique et le design d’information). Dans ce mémoire, nous étudionsl’application des principes de la Gestalt pour améliorer la compréhension de l’utilisateur des documents publics. Pour ce faire, en premier lieu, une méthode d’évaluation heuristique est adaptée pour identifier les problèmes d'utilisabilité dans les documents publics. Deuxièmement, une méthode d’analyse de documents, reposant sur des mesures des éléments visuels dans les documents, est proposée pour étudier l’application des principes de Gestalt, ainsi que les principes de conception graphique, dans les documents publics. Un échantillon de deux documents publics est utilisé pour démontrer et tester la méthodologie proposée. Sur la base des failles de conception identifiées par les deux méthodes susmentionnées, une approche minimale est proposée pour appliquer les principes de la Gestalt pour résoudre les problèmes identifiés. Les résultats obtenus montrent que l’application des principes de la Gestalt peut améliorer l'accessibilité et la compréhensibilité de l'information présentéedans les documents publics.The design of public documents playsan important role in user perception and understanding of the important information they contain. Moreover, the design of such documents can have an important impact on user self-confidence and decision making. The information design principles pertainingto how to visually structure and verbally construct documents to be easily well perceived and understood can provide valuable insights on how public documents should be designed and presented. Yet, in designing public documents there is a lack in applyingthe information design methods and frameworks. On the other hand, the Gestalt principles of perception can explain how humans organize visual elements into groups and how humans perceive and recognize patterns. Since their introduction in the early twentieth century, the Gestalt principles were examined and studied various times to improve the visual perceptual process in many application areas such as: painting, sculpture, graphic design and information design. Accordingly, this work studies the application of the Gestalt principles to improve the user understanding of public documents. To this end, first an adapted heuristic evaluation method is proposed to identify the usability problems of public documents. Secondly, based on precise measurements of thevisual elements within the documents, a document analytics method is proposed to examine the application of the Gestalt principles as well as the design principles in public documents. A sample comprising two public documents is used to test and demonstrate the proposed methodology. Based on the design flaws detected by the aforementioned two methods, a minimal approach is adopted to apply the Gestalt principles to solve the identified problems. The results obtained show that the integration of the Gestaltprinciples in the design process can improve the accessibility of information in public documents and resolve many of the usability problems in these documents

Effects of attention on a relative mislocalization with successively presented stimuli

Previous studies yielded evidence that the precision, with which stimuli are localized in the visual periphery, is improved under conditions of focused attention. The present study examined whether focused attention is able to correct a mislocalization recently observed with successively presented stimuli: when observers are asked to localize the peripheral position of a briefly presented target with respect to a previously presented comparison stimulus, they tended to judge the target as being more towards the fovea than was its actual position. In three experiments the mislocalization was tested under conditions with focused and distributed attention. Results revealed that the mislocalization increased with distributed attention and disappeared when stimuli appeared consistently at predictable positions and thus under conditions of focused attention. However, when a procedure with a trial-by-trial cueing was applied the mislocalization was only reduced, but not wiped out completely. In a recently developed dynamic field model consisting of interacting excitatory and inhibitory neuronal cell populations the results were explained as an attentional modulation of spontaneous (baseline) levels of neural activity.Fundação para a Ciência e a Tecnologia (FCT)Deutsche Forschungsgemeinschaft - DFG MU 1298/

Cortical spatio-temporal dimensionality reduction for visual grouping

The visual systems of many mammals, including humans, is able to integrate the geometric information of visual stimuli and to perform cognitive tasks already at the first stages of the cortical processing. This is thought to be the result of a combination of mechanisms, which include feature extraction at single cell level and geometric processing by means of cells connectivity. We present a geometric model of such connectivities in the space of detected features associated to spatio-temporal visual stimuli, and show how they can be used to obtain low-level object segmentation. The main idea is that of defining a spectral clustering procedure with anisotropic affinities over datasets consisting of embeddings of the visual stimuli into higher dimensional spaces. Neural plausibility of the proposed arguments will be discussed

The Impact of 2-D and 3-D Grouping Cues on Depth From Binocular Disparity

Stereopsis is a powerful source of information about the relative depth of objects in the world. In isolation, humans can see depth from binocular disparity without any other depth cues. However, many different stimulus properties can dramatically influence the depth we perceive. For example, there is an abundance of research showing that the configuration of a stimulus can impact the percept of depth, in some cases diminishing the amount of depth experience. Much of the previous research has focused on discrimination thresholds; in one example, stereoacuity for a pair of vertical lines was shown to be markedly reduced when these lines were connected to form a rectangle apparently slanted in depth (eg: McKee, 1983). The contribution of Gestalt figural grouping to this phenomenon has not been studied. This dissertation addresses the role that perceptual grouping plays in the recovery of suprathreshold depth from disparity. First, I measured the impact of perceptual closure on depth magnitude. Observers estimated the separation in depth of a pair of vertical lines as the amount of perceptual closure was varied. In a series of experiments, I characterized the 2-D and 3-D properties that contribute to 3-D closure and the estimates of apparent depth. Estimates of perceived depth were highly correlated to the strength of subjective closure. Furthermore, I highlighted the perceptual consequences (both costs and benefits) of a new disparity-based grouping cue that interacts with perceived closure, which I call good stereoscopic continuation. This cue was shown to promote detection in a visual search task but reduces depth percepts compared to isolated features. Taken together, the results reported here show that specific 2-D and 3-D grouping constraints are required to promote recovery of a 3-D object. As a consequence, quantitative depth is reduced, but the object is rapidly detected in a visual search task. I propose that these phenomena are the result of object-based disparity smoothing operations that enhance object cohesion