Psychophysical investigation of sensitivity to disparity information and of perception of 3D subjective contours in the first year of life

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In the first project phase, sensitivity for crossed horizontal disparity and perception of rivalry from 2 months of age onwards were identified. Therefore, the research continues by investigating the onset of sensitivity to uncrossed horizontal disparity (Experiment 1) and the ability to extract stereoscopically defined shapes (Experiment 2).Experiment 1 will apply the classical natural preference method of measuring looking times as well as the forced-choice preferential looking (FPL) method. The goal of this procedure is to validate the superiority of the FPL method demonstrated in the first project phase. The remaining experiments with infants will apply the habituation-dishabituation technique.Experiments 3, 4, and 5 focus on the perception of subjective contours that were enriched by stereoscopic depth information. Experiment 3 investigates infants` ability to discern 3D subjective contours. 3D subjective contours, as a consequence of adding horizontal disparity, appear to float either above or below the inducing elements. In Experiments 3 and 4, a variant of the Kanisza figure will be used.Experiment 4 deals with amodal completion processes using the object unity paradigm. The occluding surface will be a 3D subjective contour. In Experiments 3 and 4, the effect of stereoscopic depth signals will be tested by comparisons with control conditions that use pictorially specified subjective contours.Experiment 5 investigates the perception of stereoscopic subjective contours. Unlike the Kanizsa figure, these contours can be perceived under stereoscopic conditions only. This kind of subjective contours highlights both the impact of horizontal disparity and half occlusions, i.e. monocular information on depth and object coherence.In the longitudinal Experiment 1, infants between 6 and 18 weeks of age will be tested weekly. In the remaining experiments, two age groups will be tested. In the first step, infants 5-6 months of age will be assessed. If they can perform the critical performance, infants 3-4 months of age will be tested subsequently to assess whether they also display the experimental ability. Otherwise, older infants aged 7-8 months, will be investigated.A newly developed autostereoscopic monitor will be employed. This monitor is equipped with a tracking system that is also used in eye-tracking devices. Two cameras follow the infant´s eyes to determine the exact position of the infant and, as a consequence, to maintain a highly coherent stereoscopic effect.