39,352 research outputs found
Comparison and contrast in perceptual categorization
People categorized pairs of perceptual stimuli that varied in both category membership and pairwise similarity. Experiments 1 and 2 showed categorization of 1 color of a pair to be reliably contrasted from that of the other. This similarity-based contrast effect occurred only when the context stimulus was relevant for the categorization of the target (Experiment 3). The effect was not simply owing to perceptual color contrast (Experiment 4), and it extended to pictures from common semantic categories (Experiment 5). Results were consistent with a sign-and-magnitude version of N. Stewart and G. D. A. Brown's (2005) similarity-dissimilarity generalized context model, in which categorization is affected by both similarity to and difference from target categories. The data are also modeled with criterion setting theory (M. Treisman & T. C. Williams, 1984), in which the decision criterion is systematically shifted toward the mean of the current stimuli
Processing bimodal stimuli: integrality/separability of color and orientation
We examined how two distinct stimulus features, orientation and color, interact as contributions to global stimulus dissimilarity. Five subjects rated dissimilarity between pairs of bars (N = 30) varying in color (four cardinal hues, plus white) and orientation (six angles at 30° intervals). An exploratory analysis with individual-differences multidimensional scaling (MDS) resulted in a 5D solution, with two dimensions required to accommodate the circular sequence of the angular attribute, and red-green, blue-yellow and achromatic axes for the color attribute. Weights of the orientation subspace relative to the color subspace varied among the subjects, from a 0.32:0.61 ratio to 0.53:0.44, emphasis shifting between color and orientation. In addition to Euclidean metric, we modeled the interaction of color and orientation using Minkowski power metrics across a range of Minkowski exponents p, including the city-block (p = 1), Euclidean (p = 2) and Dominance metric (p â â) as special cases. For averaged data, p ~ 1.3 provided the best fit, i.e., intermediate between separable and integral features. For individual subjects, however, the metric exponent varied significantly from p = 0.7 to p = 3.1, indicating a subject-specific rule for combining color and orientation, as in Tversky and Gati's variable-weights model. No relationship was apparent between dimensional weights and individual p exponents. Factors affecting dimensional integrality are discussed, including possible underlying neural mechanisms where the interaction of the low-level vision attributes orientation and color might shift between uncorrelated (p = 1) or correlated (p â„ 2) forms
Temporal patterns of gene expression via nonmetric multidimensional scaling analysis
Motivation: Microarray experiments result in large scale data sets that
require extensive mining and refining to extract useful information. We have
been developing an efficient novel algorithm for nonmetric multidimensional
scaling (nMDS) analysis for very large data sets as a maximally unsupervised
data mining device. We wish to demonstrate its usefulness in the context of
bioinformatics. In our motivation is also an aim to demonstrate that
intrinsically nonlinear methods are generally advantageous in data mining.
Results: The Pearson correlation distance measure is used to indicate the
dissimilarity of the gene activities in transcriptional response of cell
cycle-synchronized human fibroblasts to serum [Iyer et al., Science vol. 283,
p83 (1999)]. These dissimilarity data have been analyzed with our nMDS
algorithm to produce an almost circular arrangement of the genes. The temporal
expression patterns of the genes rotate along this circular arrangement. If an
appropriate preparation procedure may be applied to the original data set,
linear methods such as the principal component analysis (PCA) could achieve
reasonable results, but without data preprocessing linear methods such as PCA
cannot achieve a useful picture. Furthermore, even with an appropriate data
preprocessing, the outcomes of linear procedures are not as clearcut as those
by nMDS without preprocessing.Comment: 11 pages, 6 figures + online only 2 color figures, submitted to
Bioinformatic
Computing von Kries Illuminant Changes by Piecewise Inversion of Cumulative Color Histograms
We present a linear algorithm for the computation of the illuminant change occurring between two color pictures of a scene. We model the light variations with the von Kries diagonal transform and we estimate it by minimizing a dissimilarity measure between the piecewise inversions of the cumulative color histograms of the considered images. We also propose a method for illuminant invariant image recognition based on our von Kries transform estimate
Three notions of tropical rank for symmetric matrices
We introduce and study three different notions of tropical rank for symmetric
and dissimilarity matrices in terms of minimal decompositions into rank 1
symmetric matrices, star tree matrices, and tree matrices. Our results provide
a close study of the tropical secant sets of certain nice tropical varieties,
including the tropical Grassmannian. In particular, we determine the dimension
of each secant set, the convex hull of the variety, and in most cases, the
smallest secant set which is equal to the convex hull.Comment: 23 pages, 3 figure
Recommended from our members
Hierarchical video summarisation in reference frame subspace
In this paper, a hierarchical video structure summarization approach using Laplacian Eigenmap is proposed, where a small set of reference frames is selected from the video sequence to form a reference subspace to measure the dissimilarity between two arbitrary frames. In the proposed summarization scheme, the shot-level key frames are first detected from the continuity of inter-frame dissimilarity, and the sub-shot level and scene level representative frames are then summarized by using k-mean clustering. The experiment is carried on both test videos and movies, and the results show that in comparison with a similar approach using latent semantic analysis, the proposed approach using Laplacian Eigenmap can achieve a better recall rate in keyframe detection, and gives an efficient hierarchical summarization at sub shot, shot and scene levels subsequently
Peacock Bundles: Bundle Coloring for Graphs with Globality-Locality Trade-off
Bundling of graph edges (node-to-node connections) is a common technique to
enhance visibility of overall trends in the edge structure of a large graph
layout, and a large variety of bundling algorithms have been proposed. However,
with strong bundling, it becomes hard to identify origins and destinations of
individual edges. We propose a solution: we optimize edge coloring to
differentiate bundled edges. We quantify strength of bundling in a flexible
pairwise fashion between edges, and among bundled edges, we quantify how
dissimilar their colors should be by dissimilarity of their origins and
destinations. We solve the resulting nonlinear optimization, which is also
interpretable as a novel dimensionality reduction task. In large graphs the
necessary compromise is whether to differentiate colors sharply between locally
occurring strongly bundled edges ("local bundles"), or also between the weakly
bundled edges occurring globally over the graph ("global bundles"); we allow a
user-set global-local tradeoff. We call the technique "peacock bundles".
Experiments show the coloring clearly enhances comprehensibility of graph
layouts with edge bundling.Comment: Appears in the Proceedings of the 24th International Symposium on
Graph Drawing and Network Visualization (GD 2016
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