Friday, August 18, 2006

Now I see it, now I don't : object and motion permanence

Cognitive Daily has a good article summarizing the findings of recent study on 4 month old babies and how they perceive moving objects.

The study utilizes the fact that babies look longer at stimuli that are interesting or what they perceive as novel. The results of the study indicate that if a moving ball is occluded by a stationary object, then the motion prior to occlusion and posterior to occlusions would be perceived as the same motion if the time of occlusion or length of occlusion is small.

This is an interesting finding from two angles. First this study necessitates that one distinguish between object permanence and motion permanence. The former seems to be an easy to achieve property relying only on the static stimuli and should be judged only by the fact as to whether a child gropes for an object that has now been occluded and is out of sight. The latter, viz. motion permanence implicitly assumes that object permanence has been achieved. It doesn't make sense to say that two motions that were temporally or spatially close are the same if the object undergoing that motion was not existent even when occluded.

Thus, these experiments provide further evidence that Piaget had misjudged the capacity of babies to achieve object permanence.

Endgame: does the existence of two visual pathways : one specialized for motion perception and other for location/shape/color/object mean that object permanence and motion permanence may be achieved at different ages and may have different underlying prognosis?

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