Does the number sense represent number?

On a now orthodox view, humans and many other animals are endowed with a “number sense”, or approximate number system (ANS), that represents number. Recently, this orthodox view has been subject to numerous critiques, with critics maintaining either that numerical content is absent altogether, or else that some primitive analog of number (‘numerosity’) is represented as opposed to number itself. We distinguish three arguments for these claims – the arguments from congruency, confounds, and imprecision – and show that none succeed. We then highlight positive reasons for thinking that the ANS genuinely represents numbers. The upshot is that proponents of the orthodox view should not feel troubled by recent critiques of their position

Perceived Texture Segregation in Chromatic Element-Arrangement Patterns: High Intensity Interference

An element-arrangement pattern is composed of two types of elements that differ in the ways in which they are arranged in different regions of the pattern. We report experiments on the perceived segregation of chromatic element-arrangement patterns composed of equal-size red and blue squares as the luminances of the surround, the interspaces, and the background (surround plus interspaces) are varied. Perceived segregation was markedly reduced by increasing the luminance of the interspaces. Unlike achromatic element-arrangement patterns composed of squares differing in lightness (Beck, Graham, & Sutter, 1991), perceived segregation did not decrease when the luminance of the interspaces was below that of the squares. Perceived segregation was approximately constant for constant ratios of interspace luminance to square luminance and increased with the contrast ratio of the squares. Perceived segregation based on edge alignment was not interfered with by high intensity interspaces. Stereoscopic cues that caused the squares composing the element arrangement pattern to be seen in front of the interspaces did not greatly improve perceived segregation. One explanation of the results is in terms of inhibitory interactions among achromatic and chromatic cortical cells tuned to spatial-frequency and orientation. Alternately, the results may be explained in terms of how the luminance of the interspaces affects the grouping of the squares for encoding surface representations. Neither explanation accounts fully for the data and both mechanisms may be involved.Air Force Office of Scientific Research (F49620-92-J-0334); Northeast Consortium for Engineering Education (A303-21-93); Office of Naval Research (N00014-91J-4100); CNPQ and NUTES/UFRJ, Brazi

Texture Segregation in Chromatic Element-Arrangement Patterns

We compare the perceived segregation of element-arrangement patterns1 which are composed of two types of squanes arranged in vertical stripes in the top and bottom regions and in a checkerboard in the middle region. The squares in a pattern are either equal in luminance and differing in hue or equal in hue and differing in luminance. Perceived segregation of squares differing in hue is not predicted by their rated similarity, but rather by the square-root of the sum of the squares of the differences in the outputs of the L-M and L+M-S opponent channels. Adaptation to the background luminance affects judgements of perceived segregation but does not affect judgments of perceived similarity. For a given background luminance, perceived segregation is a linear function of cone contrasts. Perceived hue similarity is instead a linear function of cone excitations across the background luminances. High and low luminance backgrounds decrease the perceived segregation of patterns differing in luminance. A high luminance achromatic background decreases the perceived segregation of patterns differing in hue but a low luminance achromatic background does not. The results indicate that the adaptation luminance affects the contribution of luminance differences between the two types of squares to perceived segregation but not the contribution of hue differences. For element-arrangement patterns composed of squares of equal luminance that differ in hue, perceived segregation is associated with differences in the perceived brightness of the hues. The results are consistent with the findings that the perceived segregation in element-arrangement patterns is primarily a function of the early visual mechanisms that encode pattern differences prior to the specification of the forms of the squares and their properties.Office of Naval Research (N00014-91-J-4100, N00014-94-1-0597, N00014-95-1-0409); Advanced Research Projects Agency (N00014-92-J-4015); Air Force Office of Scientific Research (F49620-92-J-0334); National Science Foundation (IIU-94-01659

Photo-Realistic Scenes with Cast Shadows Show No Above/Below Search Asymmetries for Illumination Direction

Visual search is extended from the domain of polygonal figures presented on a uniform field to photo-realistic scenes containing target objects in dense, naturalistic backgrounds. The target in a trial is a computer-rendered rock protruding in depth from a "wall" of rocks of roughly similar size but different shapes. Subjects responded "present" when one rock appeared closer than the rest, owing to occlusions or cast shadows, and "absent" when all rocks appeared to be at the same depth. Results showed that cast shadows can significantly decrease reaction times compared to scenes with no cast shadows, in which the target was revealed only by occlusions of rocks behind it. A control experiment showed that cast shadows can be utilized even for displays involving rocks of several achromatic surface colors (dark through light), in which the shadow cast by the target rock was not the darkest region in the scene. Finally, in contrast with reports of experiments by others involving polygonal figures, we found no evidence for an effect of illumination direction (above vs. below) on search times.Office of Naval Research (N00014-94-1-0597, N00014-95-1-0409

Load management strategy for Particle-In-Cell simulations in high energy particle acceleration

In the wake of the intense effort made for the experimental CILEX project, numerical simulation cam- paigns have been carried out in order to finalize the design of the facility and to identify optimal laser and plasma parameters. These simulations bring, of course, important insight into the fundamental physics at play. As a by-product, they also characterize the quality of our theoretical and numerical models. In this paper, we compare the results given by different codes and point out algorithmic lim- itations both in terms of physical accuracy and computational performances. These limitations are illu- strated in the context of electron laser wakefield acceleration (LWFA). The main limitation we identify in state-of-the-art Particle-In-Cell (PIC) codes is computational load imbalance. We propose an innovative algorithm to deal with this specific issue as well as milestones towards a modern, accurate high-per- formance PIC code for high energy particle acceleration

Approaching Visual Search in Photo-Realistic Scenes

Visual search is extended from the domain of polygonal figures presented on a uniform background to scenes in which search is for a photo-realistic object in a dense, naturalistic background. Scene generation for these displays relies on a powerful solid modeling program to define the three dimensional forms, surface properties, relative positions, and illumination of the objects and a rendering program to produce an image. Search in the presented experiments is for a rock with specific properties among other, similar rocks, although the method described can be generalized to other situations. Using this technique we explore the effects of illumination and shadows in aiding search for a rock in front of and closer to the viewer than other rocks in the scene. For these scenes, shadows of two different contrast levels can significantly deet·ease reaction times for displays in which target rocks are similar to distractor rocks. However, when the target rock is itself easily distinguishable from dis tractors on the basis of form, the presence or absence of shadows has no discernible effect. To relate our findings to those for earlier polygonal displays, we simplified the non-shadow displays so that only boundary information remained. For these simpler displays, search slopes (the reaction time as a function of the number of distractors) were significantly faster, indicating that the more complex photo-realistic objects require more time to process for visual search. In contrast with several previous experiments involving polygonal figures, we found no evidence for an effect of illumination direction on search times

Photo-Realistic Scenes with Cast Shadows Show No Above/Below Search Asymmetries for Illumination Direction

Visual search is extended from the domain of polygonal figures presented on a uniform field to photo-realistic scenes containing target objects in dense, naturalistic backgrounds. The target in a trial is a computer-rendered rock protruding in depth from a "wall" of rocks of roughly similar size but different shapes. Subjects responded "present" when one rock appeared closer than the rest, owing to occlusions or cast shadows, and "absent" when all rocks appeared to be at the same depth. Results showed that cast shadows can significantly decrease reaction times compared to scenes with no cast shadows, in which the target was revealed only by occlusions of rocks behind it. A control experiment showed that cast shadows can be utilized even for displays involving rocks of several achromatic surface colors (dark through light), in which the shadow cast by the target rock was not the darkest region in the scene. Finally, in contrast with reports of experiments by others involving polygonal figures, we found no evidence for an effect of illumination direction (above vs. below) on search times.Office of Naval Research (N00014-94-1-0597, N00014-95-1-0409

Effects of Highlights on Gloss Perception

The perception of a glossy surface in a static monochromatic image can occur when a bright highlight is embedded in a compatible context of shading and a bounding contour. Some images naturally give rise to the impression that a surface has a uniform reflectance, characteristic of a shiny object, even though the highlight may only cover a small portion of the surface. Nonetheless, an observer may adopt an attitude of scrutiny in viewing a glossy surface, whereby the impression of gloss is partial and nonuniform at image regions outside of a higlight. Using a rating scale and small probe points to indicate image locations, differential perception of gloss within a single object is investigate in the present study. Observers' gloss ratings are not uniform across the surface, but decrease as a function of distance from highlight. When, by design, the distance from a highlight is uncoupled from the luminance value at corresponding probe points, the decrease in rated gloss correlates more with the distance than with the luminance change. Experiments also indicate that gloss ratings change as a function of estimated surface distance, rather than as a function of image distance. Surface continuity affects gloss ratings, suggesting that apprehension of 3D surface structure is crucial for gloss perception.Air Force Office of Scientific Research (F49620-98-1-0108), Defense Advanced Research Projects Agency and the Office of Naval Research (N00014-95-1-0409), National Science Foundation (IIS-97-20333); Office of Naval Research (N00014-95-1-0657, N00014-01-1-0624); Whitaker Foundation (RG-99-0186

Design of Logan City\u27s Stormwater Conveyance System

This report summarizes 10th West Engineers\u27 (10WE) storm water conveyance design for Logan City. The implementation of the design mitigates flood risk due to storm water discharge , helps improve local water quality, and uses infrastructure that would otherwise be abandoned. The system collects storm water discharged along 1000 West and transports the water to the holding pond located at approximately 2400 West 2200 North, Logan, Utah (see Figure 1). Figure 1. Aerial Photo of the Area of Interest Current Conditions Logan City is located in northern Utah\u27s Cache County. As development and redevelopment occur, storm water runoff quantities will decrease due to new regulations. However, Logan City\u27s storm water system does not extend beyond 1000 West, which causes localized flooding. This project had three phases. First, 10WE collected data from both Logan City and through field investigations. Second, 10WE designed an efficient system to convey water from existing discharge locations to the holding pond. Third, 10WE completed this final report to submit to Logan City on the proposed storm water conveyance system. 10WE followed several design methods outlined in government manuals. 10WE\u27s post construction recommendations for Logan City are: 1) mow banks of each channel annually; 2) conduct a system inspection yearly and after a storm that exceeds the 20-year event to ensure that all channels and diversion structures are operating as designed. 10WE collaborated with the client, Logan City, to ensure the design satisfied all the client\u27s goals. The client had three goals: design a gravity-fed system, minimize effect on wetlands, and produce an economical design. 10WE collaborated with Cutler Engineering , who designed a treatment process for the storm water, and Westside Drainage Solutions, who designed a drainage system for a farm