Time dilation in dynamic visual display

How does the brain estimate time? This old question has led to many biological and psychological models of time perception (R. A. Block, 1989; P. Fraisse, 1963; J. Gibbon, 1977; D. L. I. Zakay, 1989). Because time cannot be directly measured at a given moment, it has been proposed that the brain estimates time based on the number of changes in an event (S. W. Brown, 1995; P. Fraisse, 1963; W. D. Poynter, 1989). Consistent with this idea, dynamic visual stimuli are known to lengthen perceived time (J. F. Brown, 1931; S. Goldstone & W. T. Lhamon, 1974; W. T. Lhamon & S. Goldstone, 1974, C. O. Z. Roelofs & W. P. C. Zeeman, 1951). However, the kind of information that constitutes the basis for time perception remains unresolved. Here, we show that the temporal frequency of a stimulus serves as the “clock” for perceived duration. Other aspects of changes, such as speed or coherence, were found to be inconsequential. Time dilation saturated at a temporal frequency of 4–8 Hz. These results suggest that the clock governing perceived time has its basis at early processing stages. The possible links between models of time perception and neurophysiological functions of early visual areas are discussed

User-Relative Names for Globally Connected Personal Devices

Nontechnical users who own increasingly ubiquitous network-enabled personal devices such as laptops, digital cameras, and smart phones need a simple, intuitive, and secure way to share information and services between their devices. User Information Architecture, or UIA, is a novel naming and peer-to-peer connectivity architecture addressing this need. Users assign UIA names by "introducing" devices to each other on a common local-area network, but these names remain securely bound to their target as devices migrate. Multiple devices owned by the same user, once introduced, automatically merge their namespaces to form a distributed "personal cluster" that the owner can access or modify from any of his devices. Instead of requiring users to allocate globally unique names from a central authority, UIA enables users to assign their own "user-relative" names both to their own devices and to other users. With UIA, for example, Alice can always access her iPod from any of her own personal devices at any location via the name "ipod", and her friend Bob can access her iPod via a relative name like "ipod.Alice".Comment: 7 pages, 1 figure, 1 tabl

Whanaungatanga: Sybil-proof routing with social networks

Decentralized systems, such as distributed hash tables, are subject to the Sybil attack, in which an adversary creates many false identities to increase its influence. This paper proposes a routing protocol for a distributed hash table that is strongly resistant to the Sybil attack. This is the first solution to this problem with sublinear run time and space usage. The protocol uses the social connections between users to build routing tables that enable Sybil-resistant distributed hash table lookups. With a social network of N well-connected honest nodes, the protocol can tolerate up to O(N/log N) "attack edges" (social links from honest users to phony identities). This means that an adversary has to fool a large fraction of the honest users before any lookups will fail. The protocol builds routing tables that contain O(N log^(3/2) N) entries per node. Lookups take O(1) time. Simulation results, using social network graphs from LiveJournal, Flickr, and YouTube, confirm the analytical results

Awareness of group performance in a CSCL-environment: Effects of peer feedback and reflection

Phielix, C., Prins, F. J., & Kirschner, P. A. (2010). Awareness of group performance in a CSCL-environment: Effects of peer feedback and reflection. Computers in Human Behavior, 26(2), 151-161. doi:10.1016/j.chb.2009.10.011This study investigated the effects of a peer feedback tool and a reflection tool on social and cognitive performance during computer supported collaborative learning (CSCL). A CSCL-environment was augmented with a peer feedback tool (Radar) and a reflection tool (Reflector) in order to make group members aware of both their individual and their group behavior. Radar visualizes how group members perceive their own social and cognitive performance and that of their peers during collaboration along five dimensions. Reflector stimulates group members to reflect upon their own performance and the performance of the group. A 2x2 factorial between-subjects design was used to examine whether Radar and Reflector would lead to better team development, more group satisfaction, lower levels of group conflict, more positive attitudes toward problem-based collaboration, and a better group product. Results show that groups with Radar perceived their team as being better developed, experienced lower conflict levels, and had a more positive attitude towards collaborative problem solving than groups without Radar. The quality of group products, however, did not differ. The results demonstrate that peer feedback on the social performance of individual group members can enhance the performance and attitudes of a CSCL-group

Group Awareness of Social and Cognitive Behavior in a CSCL Environment

Phielix, C., Prins, F. J., & Kirschner, P. A. (2010). Group awareness of social and cognitive behavior in a CSCL environment. In K. Gomez, L. Lyons, & J. Radinsky (Eds.), Learning in the Disciplines: Proceedings of the 9th International Conference of the Learning Sciences (ICLS 2010): Volume 1 (pp. 230-237). Chicago IL, USA: International Society of the Learning Sciences.This study investigated whether a peer feedback tool and a reflection tool would enhance group performance in a computer-supported collaborative learning environment. The underlying assumption was that group performance can be positively influenced by making group members aware of how their social and cognitive behavior is perceived by themselves, their peers, and the group as a whole. Participants were 120 fourth-year high school students working, with or without the tools, in dyads, triads and groups of 4 on a collaborative writing task. Results show that groups using tools perceived their team as being better developed, experienced higher levels of group satisfaction and lower levels of conflicts, than groups not using the tools. Results demonstrate that awareness, stimulated by peer assessment and reflection tools, enhances the social performance of a CSCL-group

Center–surround inhibition deepens binocular rivalry suppression

AbstractWhen dissimilar stimuli are presented to each eye, perception alternates between both images—a phenomenon known as binocular rivalry. It has been shown that stimuli presented in proximity of rival targets modulate the time each target is perceptually dominant. For example, presenting motion to the region surrounding the rival targets decreases the predominance of the same-direction target. Here, using a stationary concentric grating rivaling with a drifting grating, we show that a drifting surround grating also increases the depth of binocular rivalry suppression, as measured by sensitivity to a speed discrimination probe on the rival grating. This was especially so when the surround moved in the same direction as the grating, and was slightly weaker for opposed directions. Suppression in both cases was deeper than a no-surround control condition. We hypothesize that surround suppression often observed in area MT (V5)—a visual area implicated in visual motion perception—is responsible for this increase in suppression. In support of this hypothesis, monocular and binocular surrounds were both effective in increasing suppression depth, as were surrounds contralateral to the probed eye. Static and orthogonal motion surrounds failed to add to the depth of rivalry suppression. These results implicate a higher-level, fully binocular area whose surround inhibition provides an additional source of suppression which sums with rivalry suppression to effectively deepen suppression of an unseen rival target

How environmental protection agencies can promote eco-innovation: The prospect of voluntary reciprocal legitimacy

Abstract This paper examines the \{UK\} and Irish Environmental Protection Agencies (EPAs) ability to move beyond regulatory compliance to support and promote sustainable environmental innovation, in short “eco-innovation”. To do so would require them to overcome the perception that they face, often being perceived as ‘policemen’ by the regulated business community. We propose a new empirically-derived theoretical construct called Voluntary Reciprocal Legitimacy (VRL), defined as the development of mutual trust between the regulator and business resulting in arrangements which generate eco-innovation benefits for the regulator, the regulated business communities and society at large. \{VRL\} adds a new category to Suchman's (1995) theory of moral legitimacy as well as highlights how \{EPAs\} can build trust between themselves and regulated business, allowing a shift of the ‘beyond compliance’ legislative boundary. Such an approach supports eco-innovation whilst simultaneously protecting the natural environment

Group awareness of social and cognitive performance in a CSCL environment: Effects of a peer feedback and reflection tool

Phielix, C., Prins, F. J., Kirschner, P. A., Erkens, G., & Jaspers, J. (2011). Group awareness of social and cognitive performance in a CSCL environment: Effects of a peer feedback and reflection tool. Computers in Human Behavior, 27(3), 1087-1102. doi:10.1016/j.chb.2010.06.024A peer feedback tool (Radar) and a reflection tool (Reflector) were used to enhance group performance in a computer-supported collaborative learning environment. Radar allows group members to assess themselves and their fellow group members on six traits related to social and cognitive behavior. Reflector stimulates group members to reflect on their past, present and future group functioning, stimulating them to set goals and formulate plans to improve their social and cognitive performance. The underlying assumption was that group performance would be positively influenced by making group members aware of how they, their peers and the whole group perceive their social and cognitive behavior in the group. Participants were 108 fourth-year high school students working in dyads, triads and groups of four on a collaborative writing task, with or without the tools. Results demonstrate that awareness stimulated by the peer feedback and reflection tools enhances group-process satisfaction and social performance of CSCL-groups

Does virulence assessment of Vibrio anguillarum using sea bass (Dicentrarchus labrax) larvae correspond with genotypic and phenotypic characterization?

Background: Vibriosis is one of the most ubiquitous fish diseases caused by bacteria belonging to the genus Vibrio such as Vibrio (Listonella) anguillarum. Despite a lot of research efforts, the virulence factors and mechanism of V. anguillarum are still insufficiently known, in part because of the lack of standardized virulence assays. Methodology/Principal Findings: We investigated and compared the virulence of 15 V. anguillarum strains obtained from different hosts or non-host niches using a standardized gnotobiotic bioassay with European sea bass (Dicentrarchus labrax L.) larvae as model hosts. In addition, to assess potential relationships between virulence and genotypic and phenotypic characteristics, the strains were characterized by random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (rep-PCR) analyses, as well as by phenotypic analyses using Biolog's Phenotype MicroArray (TM) technology and some virulence factor assays. Conclusions/Significance: Virulence testing revealed ten virulent and five avirulent strains. While some relation could be established between serotype, genotype and phenotype, no relation was found between virulence and genotypic or phenotypic characteristics, illustrating the complexity of V. anguillarum virulence. Moreover, the standardized gnotobiotic system used in this study has proven its strength as a model to assess and compare the virulence of different V. anguillarum strains in vivo. In this way, the bioassay contributes to the study of mechanisms underlying virulence in V. anguillarum