Sensomotorische Interaktionen mit der Wahrnehmung menschlicher Bewegung: Wie chronischer Rückenschmerz die Wahrnehmung von Rückenbewegungen stört und die Kontrolle von Reflexen beeinflusst

The visual ability to recognize biological motion even from sparse point-light representations can be taken as evidence for a specialized perceptual mechanism. A central question in biological motion research is, how this mechanism works and on which kind of information it relies. Point-light representations of human gait (walkers) contain form as well as motion information. Perception of global walker motion (walking) can be explained by an analysis of changes of the body posture over time (form) or by an analysis of the trajectories of the local dots (motion). In the present work, the underlying mechanism is investigated in relation to the template matching model of Lange and Lappe (2006), which conceptualizes biological motion perception as mechanism based on form processing. The focus of this work lies on interference and invariance in walker perception. In the first investigation (Chapter 2), the classical dots of the walker were replaced by pictures of objects. In a reaction time task and a detection in noise task I measured the influence of the local objects on the perception of the global walker. The results showed an interference effect. Complex objects as local elements impaired the performance. Human shapes as local objects gave more impairment than any other tested object category. Inverting or scrambling the human shapes restored the performance of walking perception. Thus, object perception interferes with biological motion processing because the recognition of human form and object form shares partly the same resources in the brain. In the second investigation (Chapter 3), I addressed the question if facing and walking direction of local stick-figures, building up a global walker, influence the perception of the global walker. If the interference effect, found in the first investigation, is based on the similarity between local and global images, this effect could be detectable down to the specific level of similar facing and walking direction. Participant's performance was determined in a facing and a walking direction discrimination task. I found interference at the specific level of similar facing direction for the facing discrimination task. This effect was independent of motion of the local stick-figures. Walking direction similarity did not influence the performance, neither in facing direction discrimination nor in walking direction discrimination. The specific interference of the facing direction supports the hypothesis that the processing of body postures (form information) plays a major role in biological motion processing.