Surface perception in pictures.

Subjects adjusted a local gauge figure such as to perceptually "fit" the apparent surfaces of objects depicted in photographs. We obtained a few hundred data points per session, covering the picture according to a uniform lattice. Settings were repeated 3 times for each of 3 subjects. Almost all of the variability resided in the slant; the relative spread in the slant was about 25% (Weber fraction). The tilt was reproduced with a typical spread of about 10 degrees. The rank correlation of the slant settings of different observers was high, thus the slant settings of different subjects were monotonically related. The variability could be predicted from the scatter in repeated settings by the individual observers. Although repeated settings by a single observer agreed within 5%, observers did not agree on the value of the slant, even on the average. Scaling factors of a doubling in the depth dimension were encountered between different subjects. The data conformed quite well to some hypothetical fiducial global surface, the orientation of which was "probed" by the subject's local settings. The variability was completely accounted for by single-observer scatter. These conclusions are based upon an analysis of the internal structure of the local settings. We did not address the problem of veridicality, that is, conformity to some "real object."     

Compression of visual space in natural scenes and in their photographic counterparts

Classical theories of space perception posit continuous distortions of subjective space. These stand in contrast to the quantitatively and qualitatively different distortions experienced in space that is represented pictorially. We challenge several aspects of these theories. Comparing real-world objects with depictions of the same objects, we investigated to what extent distortions are introduced by the photographic medium. Corners of irregularly shaped buildings had to be judged in terms of the vertical dihedral angles subtended by two adjacent walls. Across all conditions, a robust effect of viewing distance was found: Building corners appear to flatten out with distance. Moreover, depictions of corners produce remarkably similar results and should not receive a different theoretical treatment than do real-world scenes. The flattening of vertical angles cannot be explained by a linear distortion of the entire visual space. We suggest that, for natural scenes, compression of space is local and dependent on contextual information.     

Team adaptation to an unforeseen system failure: Limits of the potential aids of shared knowledge and standardized communication

The present study investigates the potential benefits of a team’s shared knowledge and standardized communication in adapting to an unforeseen change by combining literature on adaptation and team performance. Each of 20 teams performed a dynamic team task and was suddenly confronted with a simulated partial system breakdown. Results show that a methodological framework designed to describe performance adaptation to an unforeseen change in individuals can also be used to model performance adaptation in teams. The system failure was followed by a performance drop and a subsequent period of gradual performance recovery. Accuracy of teams’ shared knowledge correlated positively with performance before and after the change, confirming and extending the literature on shared mental models. However, the amount of knowledge similarity did not aid teams in adapting to the unforeseen system breakdown. In addition, improving teams’ standardized communication had no damping effect on the sudden performance drop and neither helped them during the subsequent recovery period. These results show that even though shared knowledge and efficient communication are of high value to team performance and success, these characteristics are limited in aiding adaptive team performance after unforeseen unique changes that force team members to update their strategies.     

Explaining the Integration Paradox Among Small Immigrant Groups in the Netherlands

Previous studies among the four largest immigrant groups in the Netherlands suggest that higher-educated immigrants, who are more apt to integrate, actually experience more discrimination than lower-educated immigrants, which is referred to as the integration paradox. In this study, we first investigate whether this paradox also exists among smaller immigrant groups (i.e. Afghani, Iraqi, Irani, Somali, Polish and Chinese) in the Netherlands. Second, we aim to explain the educational effect on perceived personal discrimination. We derive hypotheses from a theory of exposure and a theory of rising expectations. Data are drawn from a large-scale survey (SING2009) and include close to 1,000 face-to-face interviews for each of the small ethnic minority groups. Our study supports the existence of an integration paradox for small immigrant groups in the Netherlands. Our results show that higher-educated immigrants perceive more personal discrimination, which can be attributed to their exposure to Dutch politics, their experience of relative deprivation regarding their work and education and their participation in associations.     

Using and Developing Role Plays in Teaching Aimed at Preparing for Social Responsibility

In this paper, we discuss the use of role plays in ethics education for engineering students. After presenting a rough taxonomy of different objectives, we illustrate how role plays can be used to broaden students’ perspectives. We do this on the basis of our experiences with a newly developed role play about a Dutch political controversy concerning pig transport. The role play is special in that the discussion is about setting up an institutional framework for responsible action that goes beyond individual action. In that sense, the role play serves a double purpose. It not only aims at teaching students to become aware of the different dimensions in decision making, it also encourages students to think about what such an institutional framework for responsible action might possibly look like.     

Governance Experiments in Water Management: From Interests to Building Blocks

The management of water is a topic of great concern. Inadequate management may lead to water scarcity and ecological destruction, but also to an increase of catastrophic floods. With climate change, both water scarcity and the risk of flooding are likely to increase even further in the coming decades. This makes water management currently a highly dynamic field, in which experiments are made with new forms of policy making. In the current paper, a case study is presented in which different interest groups were invited for developing new water policy. The case was innovative in that stakeholders were invited to identify and frame the most urgent water issues, rather than asking them to reflect on possible solutions developed by the water authority itself. The case suggests that stakeholders can participate more effectively if their contribution is focused on underlying competing values rather than conflicting interests.     

The visual light field

Human observers are sensitive to the '(physical) light field' in the sense that they have expectations of how a given object would appear if it were introduced in the scene in front of them at some arbitrary location. Thus the 'visual light field' is defined even in the 'empty space' between objects. In that sense the light field is akin to visual space considered as a 'container'. The visual light field at any given point can be measured in psychophysical experiments through the introduction of a suitable 'gauge object' at that position and letting the observer adjust the appearance of that gauge object (eg through suitable computer rendering) so as to produce a 'visual fit' into the scene. The parameters of the rendering will then be considered as the measurement result. We introduced white spheres as gauge objects at various locations in stereoscopically presented photographic scenes. We measured the direction ('direction of the light'), diffuseness ('quality of the light' as used by photographers and interior decorators), and intensity of the light field. We used three very different scenes, with very different physical light fields. The images were geometrically and photometrically calibrated, so we were in a position to correlate the observations with the physical 'ground truth'. We report that human observers are quite sensitive to various parameters of the physical light field and generally arrive at close to veridical settings, although a number of comparatively minor systematic deviations from veridicality can be noted. We conclude that the visual light field is an entity whose existence is at least as well defined as that of visual space, despite the fact that the visual light field hardly appears as prominently in vision science as it does in the visual arts.     

Surface perception in pictures

Subjects adjusted a local gauge figure such as to perceptually “fit” the apparent surfaces of objects depicted in photographs. We obtained a few hundred data points per session, covering the picture according to a uniform lattice. Settings were repeated 3 times for each of 3 subjects. Almost all of the variability resided in the slant; the relative spread in the slant was about 25% (Weber fraction). The tilt was reproduced with a typical spread of about 10?. The rank correlation of the slant settings of different observers was high, thus the slant settings of different subjects were monotonically related. The variability could be predicted from the scatter in repeated settings by the individual observers. Although repeated settings by a single observer agreed within 5%, observers did not agree on the value of the slant, even on the average. Scaling factors of a doubling in the depth dimension were encountered between different subjects. The data conformed quite well to some hypothetical fiducial global surface, the orientation of which was “probed” by the subject’s local settings. The variability was completely accounted for by singleobserver scatter. These conclusions are based upon an analysis of the internal structure of the local settings. We did not address the problem of veridicality, that is, conformity to some “real object.”     

Pictorial surface attitude and local depth comparisons

We measured local surface attitude for monocular pictorial relief and performed pairwise depthcomparison judgments on the same picture. Both measurements were subject to internal consistency checks. We found that both measurements were consistent with a relief (continuous pictorial surface) interpretation within the session-to-session scatter. We reconstructed the pictorial relief from both measurements separately, and found results that differed in detail but were quite similar in their basic structures. Formally, one expects certain geometrical identities that relate range and attitude data. Because we have independent measurements of both, we can attempt an empirical verification of such geometrical identities. Moreover, we can check whether the statistical scatter in the data indicates that, for example, the surface attitudes are derivable from a depth map or vice versa. We estimate that pairwise depth comparisons are an order of magnitude less precise than might be expected from the attitude data. Thus, the surface attitudes cannot be derived from a depth map as operationally defined by our methods, although the reverse is a possibility.