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

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

Bank privatization and performance - emprical evidence from Nigeria

The authors assess the effect of privatization on performance in a panel of Nigerian banks for the period 1990-2001. They find evidence of performance improvement in nine banks that were privatized, which is remarkable given the inhospitable environment for true financial intermediation. Their results also suggest negativeeffects of the continuing minority government ownership on the performance of many Nigerian banks. The authors'results complement aggregate indications of decreasing financial intermediation over the 1990s. Banks that focused on investment in government bonds and non-lending activities enjoyed a relatively higher performance.Municipal Financial Management,Banks&Banking Reform,Financial Crisis Management&Restructuring,Payment Systems&Infrastructure,International Terrorism&Counterterrorism,Banks&Banking Reform,Financial Crisis Management&Restructuring,Municipal Financial Management,Financial Intermediation,Economic Theory&Research

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

OPTIMUM NUMBER AND LOCATION OF MANUFACTURING MILK PLANTS TO MINIMIZE MARKETING COSTS

Marketing,

PRIVATE LABELING OF MILK AND THE IMPACT ON MARKET STRUCTURE

Industrial Organization,

Observations of the Gallery Habits of \u3ci\u3eTrypodendron Retusum\u3c/i\u3e (Coleoptera: Scolytidae) Infesting Aspen in Central Michigan

A monogamous pair of adult Trypodendron retusum construct a gallery system consisting of an entrance tunnel and from two to five lateral tunnels into the sapwood of aspen. Inoculation of the mutualistic fungus Ambrosiella ferruginea by the female beetle, was followed by oviposition in shallow egg cradles. Two instars were observed as the larvae enlarged their cradles. The number of cradles per gallery system was correlated to the length of the gallery system. Progeny adults with a sex ratio of approximately 1:1 emerged from late June to early August to overwinter in the litter

The McNeil Mission and the Decision to Invade Grenada

Since the invasion of Grenada in October 1983 numerous scholars have explored the military, legal, and geopolitical dimensions of Operation Urgent Fury