Reliability and consistency affect the integration of visual depth cues

Abstract Originalsprache (englisch) Visual perception relies on a two-dimensional projection of the viewed scene on the retinas of both eyes. Thus, visual depth has to be reconstructed from a number of different cues that are subsequently integrated to obtain robust depth percepts. Existing models of sensory integration are mainly based on the reliabilities of individual cues and disregard potential cue interactions. In the current study, an extended Bayesian model is proposed that takes into account both cue reliability and consistency. Four experiments were carried out to test this model's predictions. Observers had to judge visual displays of hemi-cylinders with an elliptical cross section, which were constructed to allow for an orthogonal variation of several competing depth cues. In Experiment 1 and 2, observers estimated the cylinder's depth as defined by shading, texture, and motion gradients. The degree of consistency among these cues was systematically varied. It turned out that the extended Bayesian model provided a better fit to the empirical data compared to the traditional model which disregards covariations among cues. To circumvent the potentially problematic assessment of single-cue reliabilities, Experiment 3 used a multiple-observation task, which allowed for estimating perceptual weights from multiple-cue stimuli. Using the same multiple-observation task, the integration of stereoscopic disparity, shading, and texture gradients was examined in Experiment 4. It turned out that less reliable cues were downweighted in the combined percept. Moreover, a specific influence of cue consistency was revealed. Shading and disparity seemed to be processed interactively while other cue combinations could be well described by additive integration rules. These results suggest that cue combination in visual depth perception is highly flexible and depends on single-cue properties as well as on interrelations among cues. The extension of the traditional cue combination model is defended in terms of the necessity for robust perception in ecologically valid environments and the current findings are discussed in the light of emerging computational theories and neuroscientific approaches.

Hexenfieber im Erzgebirge - Die Annaberger Krankheit 1712 - 1720

Die Arbeit untersucht das seuchenartige Auftreten von Besessenheitsfällen in Annaberg (Erzgebirge) in den Jahren 1713-1720, die Auslöser der letzten Hexenprozesse in Kursachsen waren. Zeitgenössische Beobachter stritten intensiv, ob diese sogenannte „Annaberger Krankheit“ durch Zauberei verursacht oder eine psychosomatisch bedingte Massenerkrankung war. In Abkehr von dem Vorurteil, alle Betroffenen einer solchen Massenhysterie litten an derselben Erkrankung, werden diverse Krankengeschichten rekonstruiert. Indem sich dabei Elemente von Rollenspielen (Kinderhexen, Hysterie) und Betrug (Almosenerschleichung, Denunziationen, politisch motivierte Inszenierungen) finden, zeigt sich die wundersame „Krankheit“ als nicht pathologischer sondern sozialer Vorgang. rnAm dessen Beginn stand die Geburt der Interpretation, es gäbe eine außergewöhnliche Krankheit in der Stadt, wozu akzidentielle Ereignisse mehr beitrugen als auffällige Krankheitsfälle. Gerüchtbildung und politische Instrumentalisierung bildeten den Rahmen für den Einstieg von Nachahmern, die das fiktive Krankheitsbild in die Realität eines demonstrativen Schauspiel umsetzten. Dieser Mechanismus eines selbsterfüllenden Menetekels wird vor dem Hintergrund seiner kulturellen, sozialen, ökonomischen und historischen Bedingungen detailliert rekonstruiert.