Effects of saturation and contrast polarity on the figure-ground organization of color on gray

Poorly saturated colors are closer to a pure grey than strongly saturated ones and, therefore, appear less “colorful”. Color saturation is effectively manipulated in the visual arts for balancing conflicting sensations and moods and for inducing the perception of relative distance in the pictorial plane. While perceptual science has proven quite clearly that the luminance contrast of any hue acts as a self-sufficient cue to relative depth in visual images, the role of color saturation in such figure-ground organization has remained unclear. We presented configurations of colored inducers on grey ‘test’ backgrounds to human observers. Luminance and saturation of the inducers was uniform on each trial, but varied across trials. We ran two separate experimental tasks. In the relative background brightness task, perceptual judgments indicated whether the apparent brightness of the grey test background contrasted with, assimilated to, or appeared equal (no effect) to that of a comparison background with the same luminance contrast. Contrast polarity and its interaction with color saturation affected response proportions for contrast, assimilation and no effect. In the figure-ground task, perceptual judgments indicated whether the inducers appeared to lie in front of, behind, or in the same depth with the background. Strongly saturated inducers produced significantly larger proportions of foreground effects indicating that these inducers stand out as figure against the background. Weakly saturated inducers produced significantly larger proportions of background effects, indicating that these inducers are perceived as lying behind the backgrounds. We infer that color saturation modulates figure-ground organization, both directly by determining relative inducer depth, and indirectly, and in interaction with contrast polarity, by affecting apparent background brightness. The results point towards a hitherto undocumented functional role of color saturation in the genesis of form, and in particular figure-ground percepts in the absence of chromatostereopsis

Color for the perceptual organization of the pictorial plane: Victor Vasarely's legacy to Gestalt psychology

Victor Vasarely's (1906–1997) important legacy to the study of human perception is brought to the forefront and discussed. A large part of his impressive work conveys the appearance of striking three-dimensional shapes and structures in a large-scale pictorial plane. Current perception science explains such effects by invoking brain mechanisms for the processing of monocular (2D) depth cues. Here in this study, we illustrate and explain local effects of 2D color and contrast cues on the perceptual organization in terms of figure-ground assignments, i.e. which local surfaces are likely to be seen as “nearer” or “bigger” in the image plane. Paired configurations are embedded in a larger, structurally ambivalent pictorial context inspired by some of Vasarely's creations. The figure-ground effects these configurations produce reveal a significant correlation between perceptual solutions for “nearer” and “bigger” when other geometric depth cues are missing. In consistency with previous findings on similar, albeit simpler visual displays, a specific color may compete with luminance contrast to resolve the planar ambiguity of a complex pattern context at a critical point in the hierarchical resolution of figure-ground uncertainty. The potential role of color temperature in this process is brought forward here. Vasarely intuitively understood and successfully exploited the subtle context effects accounted for in this paper, well before empirical investigation had set out to study and explain them in terms of information processing by the visual brain

Color and figure-ground: From signals to qualia

The laws which predict how the perceptual quality of figure-ground can be extracted from the most elementary visual signals were discovered by the Gestaltists, and form an essential part of their movement (see especially Metzger, 1930, and Wertheimer, 1923 translated and re-edited by Lothar Spillmann, 2009 and 2012, respectively). Distinguishing figure from ground is a prerequisite for perception of both form and space (the relative positions, trajectories, and distances of objects in the visual field. The human brain has an astonishing capacity for selecting and combining a few critical visual signals to accurately represent both form and space

Colour for behavioural success

Colour information not only helps sustain the survival of animal species by guiding sexual selection and foraging behaviour, but also is an important factor in the cultural and technological development of our own species. This is illustrated by examples from the visual arts and from state-of-the-art imaging technology, where the strategic use of colour has become a powerful tool for guiding the planning and execution of interventional procedures. The functional role of colour information in terms of its potential benefits to behavioural success across the species is addressed in the introduction here to clarify why colour perception may have evolved to generate behavioural success. It is argued that evolutionary and environmental pressures influence not only colour trait production in the different species, but also their ability to process and exploit colour information for goal-specific purposes. We then leap straight to the human primate with insight from current research on the facilitating role of colour cues on performance training with precision technology for image-guided surgical planning and intervention. It is shown that local colour cues in 2D images generated by a surgical fisheye camera help individuals become more precise rapidly across a limited number of trial sets in simulator training for specific manual gestures with a tool. The progressively facilitating effect of a local colour cue on performance evolution in a video controlled simulator task can be explained in terms of colour-based figure-ground segregation guiding attention towards local image parts, with an immediate cost on performance time, and a lasting long-term benefit in terms of greater task precision

SCIENTIFIC COMMITTEE SIXTH REGULAR SESSION ANALYSES OF JAPANESE LONGLINE OPERATIONAL CATCH AND EFFORT FOR BIGEYE TUNA IN THE WCPO

Consultant, Secretariat of the Pacific Community. Analyses of Japanese longline operational catch and effort for bigeye tuna in the WCP

Heuristic Induction of Rate-Based Process Models

Abstract This paper presents a novel approach to inductive process modeling, the task of constructing a quantitative account of dynamical behavior from time-series data and background knowledge. We review earlier work on this topic, noting its reliance on methods that evaluate entire model structures and use repeated simulation to estimate parameters, which together make severe computational demands. In response, we present an alternative method for process model induction that assumes each process has a rate, that this rate is determined by an algebraic expression, and that changes due to a process are directly proportional to its rate. We describe RPM, an implemented system that incorporates these ideas, and we report analyses and experiments that suggest it scales well to complex domains and data sets. In closing, we discuss related research and outline ways to extend the framework. Background and Motivation Reasoning about scientific domains is a high-level cognitive task that is widely viewed as requiring considerable intelligence. Over the past three decades, research on computational scientific discovery Much of the research in this area has focused on equation discovery, which has played a key role in the history of science and which has clear applications in many different disciplines. However, this task often arises in the early stages of a field's development, before theoretical knowledge supports the creation of explanatory models that account for observations in deeper terms. The task of explanatory model construction has received less attention from computational researchers, but there has been some progress on this topic. One important form of such tasks, known as inductive process modeling In the sections that follow, we review drawbacks of previous efforts on inductive process modeling, focusing on their computational expense and problems with parameter estimation. In response, we present a new approach to process model induction that adopts representational assumptions which let it carry out heuristic rather than exhaustive search through the space of model structures, making it both more efficient and more reliable. We also describe an implemented system that incorporates these ideas, and we report experimental studies that demonstrate its ability to identify relevant processes, handle noisy observations, and construct accurate models that relate many variables. We conclude by discussing our framework's relation to earlier work and proposing responses to its limitations. Critique of Process Modeling Research Research on inductive process modeling has made continual progress since its first appearance over a decade ago The first characteristic is that, even though process models are compositional in nature, current algorithms evaluate only complete model structures. This evaluation involves comparing a parameterized model's predictions with observed time series. Existing systems generate many model structures up to a given complexity level, then parameterize and evaluate each candidate in turn. This approach doe

AES-GCM-SIV: Specification and Analysis

In this paper, we describe and analyze the security of the AES-GCM-SIV mode of operation, as defined in the CFRG specification \cite{CFRG}. This mode differs from the original GCM-SIV mode that was designed in \cite{GL2015} in two main aspects. First, the CTR encryption uses a 127-bit pseudo-random counter instead of a 95-bit pseudo-random value concatenated with a 32-bit counter. This construction leads to improved security bounds when encrypting short messages. In addition, a new key derivation function is used for deriving a fresh set of keys for each nonce. This addition allows for encrypting up to $2^{50}$ messages with the same key, compared to the significant limitation of only $2^{32}$ messages that were allowed with GCM-SIV (which inherited this same limit from AES-GCM). As a result, the new construction is well suited for real world applications that need a nonce-misuse resistant Authenticated Encryption scheme. We explain the limitations of GCM-SIV, which motivate the new construction, prove the security properties of AES-GCM-SIV, and show how these properties support real usages. Implementations are publicly available in \cite{ShayGit}. We remark that AES-GCM-SIV is already integrated into Google\u27s BoringSSL library \cite{BoringSSL}, and its deployment for ticket encryption in QUIC \cite{QUIC} is underway

Partitioning direct and indirect effects reveals the response of water-limited ecosystems to elevated CO2

Increasing concentrations of atmospheric carbon dioxide are expected to affect carbon assimilation and evapotranspiration (ET), ultimately driving changes in plant growth, hydrology and the global carbon balance. Direct leaf biochemical effects have been widely investigated, while indirect effects, although documented, elude explicit quantification in experiments. Here, we used a mechanistic model to investigate the relative contributions of direct (through carbon assimilation) and indirect (via soil moisture savings due to stomatal closure, and changes in leaf area index, LAI) effects of elevated CO2 across a variety of ecosystems. We specifically determined which ecosystems and climatic conditions maximise the indirect effects of elevated CO2. The simulations suggest that the indirect effects of elevated CO2 on net primary productivity are large and variable, ranging from less than 10% to more than 100% of the size of direct effects. For ET, indirect effects were on average 65% of the size of direct effects. Indirect effects tended to be considerably larger in water-limited ecosystems. As a consequence, the total CO2 effect had a significant, inverse relationship with the wetness index and was directly related to vapor pressure deficit. These results have major implications for our understanding of the CO2-response of ecosystems and for global projections of CO2 fertilization because, while direct effects are typically understood and easily reproducible in models, simulations of indirect effects are far more challenging and difficult to constrain. Our findings also provide an explanation for the discrepancies between experiments in the total CO2 effect on net primary productivity

Fetal and neonatal exposure to trans fatty acids impacts on susceptibility to atherosclerosis in apolipoprotein E*3 Leiden mice

Nutrition during pregnancy can impact on the susceptibility of the offspring to cardiovascular disease. Postnatal consumption of trans fatty acids (TFA), associated with partially hydrogenated vegetable oil (PHVO), increases the risk of atherosclerosis, while evidence for those trans fatty acids associated with ruminant-derived dairy and meat remain equivocal. Here, we investigate the impact of maternal consumption of dietary PHVO (P) and ruminant milk fat (R) on the development of atherosclerosis in their offspring, using the transgenic apoE*3 Leiden mouse. Dams were fed either chow (C) or one of three high fat diets: a diet reflecting the saturated fatty acid content of a ‘Western’ diet (W) or one enriched with either P or R. Diets were fed during either pregnancy alone or pregnancy and lactation. Weaned offspring were then transferred to an atherogenic diet for twelve weeks. Atherosclerosis was assessed as lipid staining in cross-sections of the aorta. There was a significant effect of maternal diet during pregnancy on development of atherosclerosis (p=0.013) in the offspring with those born of mothers fed R or P during pregnancy displaying smaller lesions that those fed C or W. This was not associated with changes in total or lipoprotein cholesterol. Continuing to feed P during lactation increased atherosclerosis compared to that seen in offspring of dams fed P only during pregnancy (p<0.001). No such effect was seen in those from mothers fed R (p=0.596) or W (p=901). We conclude that dietary TFA have differing effects on cardiovascular risk at different stages of the lifecycle

Fire, Hurricane and Carbon Dioxide: Effects on Net Primary Production of a Subtropical Woodland

Disturbance affects most terrestrial ecosystems and has the potential to shape their responses to chronic environmental change. Scrub-oak vegetation regenerating from fire disturbance in subtropical Florida was exposed to experimentally elevated carbon dioxide (CO2) concentration (+350ll-1) using open-top chambers for 11yr, punctuated by hurricane disturbance in year 8. Here, we report the effects of elevated CO2 on aboveground and belowground net primary productivity (NPP) and nitrogen (N) cycling during this experiment. The stimulation of NPP and N uptake by elevated CO2 peaked within 2yr after disturbance by fire and hurricane, when soil nutrient availability was high. The stimulation subsequently declined and disappeared, coincident with low soil nutrient availability and with a CO2-induced reduction in the N concentration of oak stems. These findings show that strong growth responses to elevated CO2 can be transient, are consistent with a progressively limited response to elevated CO2 interrupted by disturbance, and illustrate the importance of biogeochemical responses to extreme events in modulating ecosystem responses to global environmental change