Object knowledge modulates colour appearance

We investigated the memory colour effect for colour diagnostic artificial objects. Since knowledge about these objects and their colours has been learned in everyday life, these stimuli allow the investigation of the influence of acquired object knowledge on colour appearance. These investigations are relevant for questions about how object and colour information in high-level vision interact as well as for research about the influence of learning and experience on perception in general. In order to identify suitable artificial objects, we developed a reaction time paradigm that measures (subjective) colour diagnosticity. In the main experiment, participants adjusted sixteen such objects to their typical colour as well as to grey. If the achromatic object appears in its typical colour, then participants should adjust it to the opponent colour in order to subjectively perceive it as grey. We found that knowledge about the typical colour influences the colour appearance of artificial objects. This effect was particularly strong along the daylight axis

Learning to Use Illumination Gradients as an Unambiguous Cue to Three Dimensional Shape

The luminance and colour gradients across an image are the result of complex interactions between object shape, material and illumination. Using such variations to infer object shape or surface colour is therefore a difficult problem for the visual system. We know that changes to the shape of an object can affect its perceived colour, and that shading gradients confer a sense of shape. Here we investigate if the visual system is able to effectively utilise these gradients as a cue to shape perception, even when additional cues are not available. We tested shape perception of a folded card object that contained illumination gradients in the form of shading and more subtle effects such as inter-reflections. Our results suggest that observers are able to use the gradients to make consistent shape judgements. In order to do this, observers must be given the opportunity to learn suitable assumptions about the lighting and scene. Using a variety of different training conditions, we demonstrate that learning can occur quickly and requires only coarse information. We also establish that learning does not deliver a trivial mapping between gradient and shape; rather learning leads to the acquisition of assumptions about lighting and scene parameters that subsequently allow for gradients to be used as a shape cue. The perceived shape is shown to be consistent for convex and concave versions of the object that exhibit very different shading, and also similar to that delivered by outline, a largely unrelated cue to shape. Overall our results indicate that, although gradients are less reliable than some other cues, the relationship between gradients and shape can be quickly assessed and the gradients therefore used effectively as a visual shape cue

A neuroscientific approach to exploring fundamental questions in VR

Virtual reality presents a new set of challenges and opportunities for both engineers and neuroscientists. Here we provide an overview of a programme designed by a group of psychologists, neuroscientists and VR specialists to address some of the most outstanding issues in the field ranging from the very low-level (for example, how the brain processed motion-in-depth signals generated by stereoscopic display devices) to the very high level (how virtual environments can lead to a sense of immersion and emotional engagement). We present data from psychophysical, electrophysiological and neuroimaging experiments and explain how different research methodologies can be applied to different problems in the field of VR/AR. We end by describing an open-source, extensible software package for studying issues in VR that can interface to common laboratory measurement equipment and discussing future directions and challenges facing the neuroscience and VR engineering communities

How Do Reliability and Timing Influence Cue-Combinations for Shading and Stereo-Disparity?

Cue-conflict studies have been used with considerable success to examine the mechanisms underlying the integration of different sensory cues. Our recent studies have used these methods to examine the combination of stereo-disparity and shading cues in realistically rendered stimuli. The stimuli featured circular convexities with cyclopean shading and a stereo-cue based upon a densely dotted surface texture—other cues (shape outline and surface texture gradient) were controlled for. In our first experiment observers made depth discriminations while disparity noise was manipulated; we were able to demonstrate that for most observers cues are combined optimally—ie, PSEs and response variances shifted towards the more reliable channel. In a follow-on study we have examined how these cue-combinations are affected by presentation timing—with forwards and backwards masking. For most observers the adage that shading provides a quick and dirty mechanism for making depth judgements seems to be supported. Observers can make reliable depth judgements based upon shading when the difference in depth is relatively fine. However, for fine discriminations more time is required, and by this time the more accurate information from the stereo-channel has become available and is used

Interactions between shading and disparity for depth perception

A classic way to study different aspects of perception is to consider how information from different cues is combined to generate a percept. Artists and others use luminance gradients (shading) to provide a sense of depth and shape in images. Here we report on studies examining factors that influence the combination of depth cues defined by monocular shading and the well studied depth cue of binocular disparity. Ray-traced images (RADIANCE) were created either featuring a smooth surface illuminated from above (shading-channel), or a surface defined by small spheres (disparity-channel). The shading- and disparity-defined pairs were combined by placing dots in the stimulus image, superimposed upon the shaded surface, at the locations of the spheres, resulting in veridical shading and binocular disparity. By independently varying the depth delivered by these channels, we created stimuli with conflicting depth-defined and shading-defined information. We find that when disparity and shape information are combined for depth perception, disparity information does not dominate perception. Under some circumstances, PSEs for depth judgments reflect values that lie between the two conflicting cues. The combination of depth cues is influenced by the extent of the overall discrepancy, larger conflicts appear to force the identification of dual-layers rather than a combined surface

Participation as a mechanism to favour psychological empowerment and positive interaction: The “Ágora Infantil” participatory democracy programme

This investigation aims to show the relationship between participation and psychological empowerment and between participation and interaction under an institutional political participation programme. This initiative known as Ágora Infantil (AI) is characterised by an obligatory draw‐ based deliberative participation methodology with superordinate goals based on group dynamics, with games playing a central role. The evaluation was carried out using a quasi‐experimental design, with quantitative measurements of the experimental and control groups, along with systematic observation of the target group. The results support the hypotheses proposed: Participation in the AI programme led to an increase in psychological empowerment and positive interactions between the participants. These results offer information as to what design should be used for these types of political initiatives to favour inclusion and empowerment of children, while at the same time improving classroom relationships