Article Summary: Event Categorization in Infancy: Renee Baillargeon, Su-hua Wang

            This article focuses on early infant cognition, mainly their ability to sort information about their physical world into categories.  The categories studied in this article were about things that can happen to objects such as containment and occlusion. Containment is described as an object being put inside another object and occlusion is described as an object being hidden by another object.  The article suggests that infants have certain expectations about physical events that occur.

            The first series of experiments that were conducted looked at height in occlusion and containment. An object was lowered behind and occluder and then behind a containment. In the expected event the occluder and container were as tall as the object, but in the unexpected event the occluder and container were only half as tall as the object.  The infants that witnessed each event, but they did not look as long at the expected event as they did the unexpected event in the occlusion trial. This suggests that the object not being hidden by the occluder surprised them.  Height occlusion and containment are two different categories and infants do not generalize across the two even though they look similar in physical characteristics. Similar experiments revealed that it is not until about 7.5 months in age when infants begin to consider height when they are predicting events. Also it is not until about 12 months that infants consider the height of an object and whether it can fully covered or not.

            Another experiment discussed in this article looked at transparency in occlusion and containment.  In this experiment infants looked at either a transparent occluder or a transparent container. A shorter object was lowered behind a screen into the container or behind the occluder. When the screen was dropped it revealed either the transparent container or the transparent occluder. In the expected event the object was visible through the transparent occluder or container. In the unexpected event the object was not visible. The results of this experiment showed that infants looked longer at the unexpected occlusion event. At 7.5 month of age infants realize than an object placed behind a transparent occluder should remain visible, but it is not until about 10 months of age to do they realize that an object should also remain visible in a container.

            Infants can also be primed to attend to relative heights and objects. The infants were first exposed to the event as an occlusion event where the occluder was slid in front of the objects. The occluder was removed and the object was covered with a container lowered over top of it. The infants looked longer at the unexpected event, which suggested that the priming of the infants to attend to height information helped them determine the violation in the unexpected. When reviewing an event infant will place their knowledge of what is happening into a category and then review the information in the categories.

            This article brings up an interesting idea that infants sort information about their world into categories.  I wonder if the categories develop as an infant becomes habituated to an event occurring in their physical world? If an infant can consistently see and object through a transparent occluder then they become habituated to the object always being there. As the experiment is being conducted the infant does not attend to the event as long because they have been habituated to objects being visible in their physical world. It is not something new. When the object fails to be visible behind a transparent occluder they attend longer because it is an unexpected event. They haven’t been habituated to this event.