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151.
Most research on visual space has been done under restricted viewing conditions and in reduced environments. In our experiments, observers performed an exocentric pointing task, a collinearity task, and a parallelity task in a entirely visible room. We varied the relative distances between the objects and the observer and the separation angle between the two objects. We were able to compare our data directly with data from experiments in an environment with less monocular depth information present. We expected that in a richer environment and under less restrictive viewing conditions, the settings would deviate less from the veridical settings. However, large systematic deviations from veridical settings were found for all three tasks. The structure of these deviations was task dependent, and the structure and the deviations themselves were comparable to those obtained under more restricted circumstances. Thus, the additional information was not used effectively by the observers. 相似文献
152.
We examined the haptic perception of orientations of a single bar throughout the horizontal plane using a verbal response: participants were to assign a number of minutes to the orientation of a bar defined with respect to the stimulus table. Performance was found to be systematically biased. Deviations were consistent with, yet much smaller than, those resulting from haptic motor matching tasks. The size and direction of the deviations were found to correlate with hand orientation, and not to depend on spatial location per se, suggesting a role for hand-centred reference frames in biasing performance. Delaying the response by 10 s led to a small improvement only of right-hand perceptions, indicating different hemispheric involvement in processes involved in retaining and/or recoding of haptic orientation information. Also the haptic oblique effect was found with the current verbal response. Importantly, it was affected neither by hand orientation nor by delay, suggesting that the oblique effect is independent of the aforementioned deviations in orientation perception. 相似文献
153.
In order to assess the influence of illumination direction on shape constancy, we studied the pictorial relief of computer images of globular 3-D objects. We used two globally convex objects, one with a furrow and one with a dimple. Observers adjusted local surface attitude probes at 200-250 different locations in the image such that they seemed to lie on the pictorial surface. We manipulated the viewing direction and the illumination direction in a 2 x 2 orthogonal design. Viewing directions were chosen such that the image contained only a few, or no, contour singularities. Changes in the illumination direction were found to induce systematic changes in the settings for both viewing directions. Effects were especially pronounced for images that had no contour singularities. The results showed that a change in the illumination direction can change the local shape of the pictorial relief in addition to the bas-relief ambiguities of scaling and shearing in depth. We found that concavities in the pictorial relief are associated with the darker areas in the image. The deviation from shape constancy cannot be explained by bas-relief ambiguity since the required transformation between the shapes is nonlinear. 相似文献
154.
155.
Abstract— Most existing computational models of the visual perception of three-dimensional shape from texture are based on assumed constraints about how texture is distributed on visible surfaces. The research described in the present article was designed to investigate how violations of these assumptions influence human perception. Observers were presented with images of smoothly curved surfaces depicted with different types of texture, whose distribution of surface markings could be both anisotropic and inhomogeneous. Observers judged the pattern of ordinal depth on each object by marking local maxima and minima along designated scan lines. They also judged the apparent magnitudes of relative depth between designated probe points on the surface. The results revealed a high degree of accuracy and reliability in all conditions, except for a systematic underestimation of the overall magnitude of surface relief. These findings suggest that human perception of three-dimensional shape from texture is much more robust than would be reasonable to expect based on current computational models of this phenomenon. 相似文献
156.
CB1 cannabinoid receptors modulate kinase and phosphatase activity during extinction of conditioned fear in mice
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Cannich A Wotjak CT Kamprath K Hermann H Lutz B Marsicano G 《Learning & memory (Cold Spring Harbor, N.Y.)》2004,11(5):625-632
Cannabinoid receptors type 1 (CB1) play a central role in both short-term and long-term extinction of auditory-cued fear memory. The molecular mechanisms underlying this function remain to be clarified. Several studies indicated extracellular signal-regulated kinases (ERKs), the phosphatidylinositol 3-kinase with its downstream effector AKT, and the phosphatase calcineurin as potential molecular substrates of extinction behavior. To test the involvement of these kinase and phosphatase activities in CB1-dependent extinction of conditioned fear behavior, conditioned CB1-deficient mice (CB1(-/-)) and wild-type littermates (CB1(+/+)) were sacrificed 30 min after recall of fear memory, and activation of ERKs, AKT, and calcineurin was examined by Western blot analysis in different brain regions. As compared with CB1(+/+), the nonreinforced tone presentation 24 h after auditory-cued fear conditioning led to lower levels of phosphorylated ERKs and/or calcineurin in the basolateral amygdala complex, ventromedial prefrontal cortex, dorsal hippocampus, and ventral hippocampus of CB1(-/-). In contrast, higher levels of phosphorylated p44 ERK and calcineurin were observed in the central nucleus of the amygdala of CB1(-/-). Phosphorylation of AKT was more pronounced in the basolateral amygdala complex and the dorsal hippocampus of CB1(-/-). We propose that the endogenous cannabinoid system modulates extinction of aversive memories, at least in part via regulation of the activity of kinases and phosphatases in a brain structure-dependent manner. 相似文献
157.
Shape-from-shading for matte and glossy objects 总被引:1,自引:0,他引:1
We wanted to find out whether the presence of specular highlights on the otherwise matte objects would make a difference to the perceived surface relief. Six different, globally convex objects were displayed on a computer screen. The depicted objects were either matte or glossy and were illuminated from one of the two different directions. Shape-from-shading was evaluated with two different paradigms. In Experiment 1 observers were asked to set a number of local surface attitude probes such that the probes looked as if they were tangent to the objects' surfaces. In Experiment 2, observers were instructed to make traces of the contours of the depicted objects in the horizontal and vertical planes. Although the two tasks target different aspects of the perceived surface, they give essentially similar results here. In both tasks we found differences that were induced by changing the illumination direction. Surprisingly, no systematic difference was found between the results for matte and glossy objects. We must, therefore, conclude that there is no evidence from the current study that glossiness influences shape perception although to the observer matte and glossy objects look quite different. 相似文献
158.
We investigated the structure of visual space with a 3D exocentric pointing task. Observers had to direct a pointer towards a ball. Positions of both objects were varied. We measured the deviations from veridical pointing-directions in the horizontal and vertical planes (slant and tilt resp.). The slant increased linearly with an increasing horizontal visual angle. We also examined the effect of relative distance, i.e., the ratio of the distances between the two objects and the observer. When the pointer was further away from the observer than the ball, the observer directed the pointer in between himself and the ball, whereas when the pointer was closer to the observer he directed the pointer too far away. Neither the horizontal visual angle nor the relative distance had an effect on the tilt. The vertical visual angle had no effect on the deviations of the slant, but had a linear effect on the tilt. These results quantify the anisotropy of visual space. 相似文献
159.
Personality in cyberspace: personal Web sites as media for personality expressions and impressions 总被引:1,自引:0,他引:1
This research examined the personality of owners of personal Web sites based on self-reports, visitors' ratings, and the content of the Web sites. The authors compared a large sample of Web site owners with population-wide samples on the Big Five dimensions of personality. Controlling for demographic differences, the average Web site owner reported being slightly less extraverted and more open to experience. Compared with various other samples, Web site owners did not generally differ on narcissism, self-monitoring, or self-esteem, but gender differences on these traits were often smaller in Web site owners. Self-other agreement was highest with Openness to Experience, but valid judgments of all Big Five dimensions were derived from Web sites providing rich information. Visitors made use of quantifiable features of the Web site to infer personality, and the cues they utilized partly corresponded to self-reported traits. 相似文献
160.
Line gratings were used to investigate the tactual discrimination thresholds for line frequency. In Experiment 1, participants were asked to discriminate between two gratings, each with a different line frequency. We used four standard frequencies in the eightfold range from 0.5 to 4 lines/cm. Thresholds were found to be constant at about 10.6%. In this experiment, we also measured hand speed and contact force. Hand speed was roughly in the range between 0.12 and 0.44 m/sec; contact force ranged from 0.62 to 2.76 N. In Experiment 2, we determined discrimination thresholds for line frequency transitions within a single grating. We used two frequencies and three transition lengths. The transition length had no effect on the threshold. In a third experiment, line frequency was modulated periodically. Varying the standard frequency and the size of the modulation period was found to have no effect on the discrimination thresholds. We conclude three things. First, Weber fractions for line frequency discrimination decrease as a function of line frequency within the experimental range. Second, discrimination thresholds are not altered by the length of the transition between two adjacent gratings with different line frequencies. And finally, the size of a modulation period in periodically modulated gratings is of no influence on the modulation detection threshold. 相似文献