When, Where and What : The Development of Perceived Spatio-Temporal Continuity

Sammanfattning: This thesis explored the development of infants’ ability to preserve spatio-temporal continuity of moving objects in situations where they disappeared completely (Study I & II) or partially (Study III) behind other objects (occluders). We recorded infants gaze direction with the help of two different techniques: 1) infants’ gaze shifts in Study I were measured with electro-oculogram (EOG) in combination with a motion analyzing system (Qualisys) that recorded the reflected infrared light from markers placed on the infant’s head and the moving object; 2) in Studies II and III a cornea reflection eye tracker was used (Tobii 1750) . The results presented in this thesis demonstrate that 4-month-old infants are able to represent the temporal aspects of object motion during different periods of complete occlusion (Study I). At 6 months of age infants are able not only to predict the time when a moving object will reappear after complete occlusion but they are also capable to extrapolate pre-occlusion trajectory of the moving object and, thus, to accurately predict its reappearance (Study II). Moreover, in the situation where a linear pre-occlusion trajectory of the moving object is violated (the object turns by 90 degrees behind the occluder), infants at this age are capable of rapidly learning this new experience and base their future gaze shifts over occluder on the newly acquired knowledge. They are also able to preserve this new experience over a 24-hour period. In the situations where occlusion is not complete and some visual information is still available (Study III), 9-month-old infants and to a lesser extent 5-month-old infants are able to reconstruct the moving pattern and to follow its direction of motion with the smooth eye movements. Moreover, 9-month-olds are capable to produce such smooth pursuit at an adult-like level.