Doctor of Philosophy (PhD)
The unit of representation in visual working memory (VWM) is a matter of some debate. The object benefit occurs when more features are remembered when they are combined into fewer objects. This has been used to support the perspective that objects are the unit of representation in VWM. However, the object benefit occurs only for two features from different dimensions (e.g., a blue circle: color and shape) but not two features from the same dimension (e.g., a red-and-blue bi-colored square: two colors). This suggests that both objects and features may be important in determining VWM capacity. The purpose of this study was to compare the object hypothesis against a new, alternative unit of representation: the Boolean map. A Boolean map is a spatial representation that can also carry information about features, although feature tags must be applied to an entire map. The Boolean map distinguishes between features that must be accessed serially and features that can be accessed in parallel: features that can be accessed in parallel can be represented on the same map, while features that are accessed serially must be represented on different maps. Three experiments were conducted to explore both hypotheses. In Experiment 1, the hypothesis that some types of stimuli are not attended as objects was examined by testing object-based attention for different kinds of objects. In Experiment 2, the Boolean map hypothesis was tested by examining which features can be accessed in parallel and which features must be accessed serially. Finally, in Experiment 3, the object benefit in VWM was tested for the same stimuli used in Experiments 1 and 2. The results showed that even objects that did not show an object benefit in VWM in Experiment 3 were still attended as objects in Experiment 1. However, only features that could be attended in parallel when combined into an object (Experiment 2) showed an object benefit in VWM (Experiment 3). These results suggesting that the unit of representation is restricted by the features that can be accessed in parallel, in support of the Boolean map hypothesis.
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van Lamsweerde, Amanda Elaine, "What you attend to is what you remember : investigating the unit of representation in visual working memory" (2013). LSU Doctoral Dissertations. 3934.