Tuan Tran, Ph.D. (2006)

Past research on emotion and cognition has primarily focused on attention and long-term memory. Only recently has the focus been directed at working memory. The aim of this thesis was to contribute to the growing understanding of how emotion affects working memory, particularly controlled attention. To achieve this aim, this thesis explored four general questions: (1) Can individuals focus on what is important (i.e., task-relevant) and disregard what is not important (i.e., task-irrelevant) information, particularly when the irrelevant information is emotionally laden? (2) To what degree do individual differences (i.e., emotional states and dysphoria---mild depression) influence an individual's ability to actively ignore task-irrelevant information? (3) Does the extent to which an individual is able to inhibit task-irrelevant information from working memory predict how much negative emotional arousal the person will experience later when watching a negative arousing film clip? (4) Do sad and happy emotions consume more attentional resources than neutral emotion? Two experiments were designed to explore these questions using a Modified Sternberg Task (MST). Experiment 1 found that participants in the sad condition (especially those classified as having dysphoria) have the most difficulty inhibiting the interference of irrelevant information compared to participants in the neutral and happy conditions. Furthermore, the ability to inhibit task-irrelevant information did not predict future negative emotional experiences. To examine whether Experiment 1 results were due to the sad emotion (as well as dysphoria) reducing attentional capacity, Experiment 2 utilized a dual-task paradigm by embedding a secondary task (i.e., size judgment) in the MST. Contrary to the Experiment 1 results, under secondary task load sad and dysphoric participants were more successful in inhibiting the interference of irrelevant information compared to participants in the neutral and happy conditions. Results from the two experiments are discussed in terms of a "distraction effect" observed in the literature (i.e., the secondary task disrupts the rumination of negative events by sad and dysphoric participants, leaving more attentional capacity available for the primary task) as well as providing a new perspective in explaining several emotion and behavioral effects (e.g., mood congruence effect).