We discuss a variety of psychophysical experiments that explore di erent aspects of the problem of object recognition and representation in human vision. In all experiments, subjects were presented with realistically rendered images of computer-generated three-dimensional objects, with tight control over stimulus shape, surface properties, illumination, and viewpoint, as well as subjects' prior exposure to the stimulus objects. Contrary to the predictions of the paradigmatic theory of recognition, which holds that object representations are viewpoint i n v ariant, performance in all experiments was consistently viewpoint dependent, was only partially aided by binocular stereo and other depth information, was speci c to viewpoints that were familiar, and was systematically disrupted by rotation in depth more than by deforming the two-dimensional images of the stimuli. The emerging concept of multipleviews representation supported by these results is consistent with recently advanced computational theories of recognition based on view interpolation. Moreover, in several simulated experiments employing the same stimuli used in experiments with human subjects, models based on multiple-views representations replicated many of the psychophysical results concerning the observed pattern of human performance.

Newborns with Pierre Robin sequence (PRS) have mandibular hypoplasia, glossoptosis, and possibly cleft palate. Their facial appearance is characteristic. The further facial development is controversial. The aim of this study was to analyze the facial development of children with PRS.In a prospective, cross-sectional study, 344 healthy children and 37 children with PRS and cleft palate younger than 8 years were scanned three-dimensionally. Twenty-one standard anthropometric landmarks were identified, and the images were superimposed. Growth curves for normal facial development were calculated. The facial morphology of children with PRS was compared with that of healthy children.The facial growth of children with PRS in the transversal and vertical direction was normal. In the sagittal direction, the mandibular deficit was confirmed. Except for the orbital landmarks and nasion, all landmarks of the midface demonstrated a significant sagittal deficit. This difference to healthy children remained constant for all ages.Our study cannot support the theory of mandibular catch-up growth. The sagittal deficit of the midface could be observed in all ages. This indicates that children with PRS have a very early, severe, and persistent underdevelopment of this part of the face. We conclude that this disturbance must be addressed in early childhood with orthodontic and speech therapy.

The Bayesian approach to vision provides a fruitful theoretical framework for integrating different depth modules. In this formulation depth can be represented by one or more surfaces. Prior probabilities, corresponding to natural constraints, can be defined on these surfaces to avoid the ill-posedness of vision. We advocate strong coupling between different depth cues, so that the different modules can interact during computation. This framework is rich enough to accommodate straightforwardly both consonant and contradictory cue integration, by the use of binary decision units. These units can be interpreted in terms of robust statistics. A number of existing psychophysical experiments can be understood within this framework.

We have developed a computer system for reconstructing and analyzing three dimensional flight trajectories of flies. Its application to the study of the free flight behaviour of the fruitfly Drosophila melanogaster is described. The main results are: a) Drosophila males only occasionally track other flies; b) in such cases the fly’s angular velocity is a function of the error angle under which the leading fly is seen; c) body saccades can be demonstrated during cruising flights; d) high angular velocities are strongly correlated with low forward velocities, probably reflecting an aerodynamic constraint of flight. The 3-D technique described may provide an adequate tool for studying the organization of the systems present in flies and for relating the free flight behaviour to previous analyses of tethered flies.

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