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Predictive tracking over occlusions by 4-month-old infants
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Psychology.
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Psychology.
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Psychology.
2007 (English)In: Developmental Science, ISSN 1363-755X, E-ISSN 1467-7687, Vol. 10, no 5, 625-640 p.Article in journal (Refereed) Published
Abstract [en]

Two experiments investigated how 16-20-week-old infants visually tracked an object that oscillated on a horizontal trajectory with a centrally placed occluder. To determine the principles underlying infants' tendency to shift gaze to the exiting side before the object arrives, occluder width, oscillation frequency, and motion amplitude were manipulated resulting in occlusion durations between 0.20 and 1.66 s. Through these manipulations, we were able to distinguish between several possible modes of behavior underlying 'predictive' actions at occluders. Four such modes were tested. First, if passage-of-time determines when saccades are made, the tendency to shift gaze over the occluder is expected to be a function of time since disappearance. Second, if visual salience of the exiting occluder edge determines when saccades are made, occluder width would determine the pre-reappearance gaze shifts but not oscillation frequency, amplitude, or velocity. Third, if memory of the duration of the previous occlusion determines when the subjects shift gaze over the occluder, it is expected that the gaze will shift after the same latency at the next occlusion irrespective of whether occlusion duration is changed or not. Finally, if infants base their pre-reapperance gaze shifts on their ability to represent object motion (cognitive mode), it is expected that the latency of the gaze shifts over the occluder is scaled to occlusion duration. Eye and head movements as well as object motion were measured at 240 Hz. In 49% of the passages, the infants shifted gaze to the opposite side of the occluder before the object arrived there. The tendency to make such gaze shifts could not be explained by the passage of time since disappearance. Neither could it be fully explained in terms of visual information present during occlusion, i.e. occluder width. On the contrary, it was found that the latency of the pre-reappearance gaze shifts was determined by the time of object reappearance and that it was a function of all three factors manipulated. The results suggest that object velocity is represented during occlusion and that infants track the object behind the occluder in their 'mind's eye'.

Place, publisher, year, edition, pages
2007. Vol. 10, no 5, 625-640 p.
National Category
Psychology
Identifiers
URN: urn:nbn:se:uu:diva-95613DOI: 10.1111/j.1467-7687.2007.00604.xISI: 000248594800012PubMedID: 17683347OAI: oai:DiVA.org:uu-95613DiVA: diva2:169904
Available from: 2007-04-05 Created: 2007-04-05 Last updated: 2011-01-24Bibliographically approved
In thesis
1. When, Where and What: The Development of Perceived Spatio-Temporal Continuity
Open this publication in new window or tab >>When, Where and What: The Development of Perceived Spatio-Temporal Continuity
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Social Sciences, ISSN 1652-9030 ; 24
Keyword
Psychology, infants, occlusion, incomplete visual information, saccadic gaze shifts, smooth pursuit, temporal, spatial, object representation, learning, extrapolation, Psykologi
Identifiers
urn:nbn:se:uu:diva-7760 (URN)978-91-554-6834-7 (ISBN)
Public defence
2007-04-27, Sal IV, Universitets huset, Övre Slottsgatan 2, Uppsala, 13:15
Opponent
Supervisors
Available from: 2007-04-05 Created: 2007-04-05 Last updated: 2011-01-24Bibliographically approved

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