The deceits of visual short-term memory: Behavior, computational modeling and electrophysiology

Visual memory is vulnerable to the influence of task-irrelevant information, and visual attention's importance for visual memory lies in attention's ability to selectively foreground task-relevant information, while filtering out what is not. This thesis comprises a set of experiments that explored different aspects of task-irrelevant information's influence on visual memory and its interaction with attention, using recognition and recall tests, as well as electrophysiology technique. In the first study, I investigated how a to-be-ignored task-irrelevant stimulus attribute affects recognition judgments. It is shown that attentional selectivity is imperfect, the failure of attention in memory allows the irrelevant stimulus attribute to infiltrate and undermine recognition accuracy and associated response times. Through a summed-similarity model of visual recognition, NEMo, I found that irrelevant information operates on the early stage of memory processing, but not at a later stage that supports decision making. In the second study, the exploration of visual memory's precision and its vulnerability to irrelevant information's influences is aided by a direct matching paradigm. I found that the recall of a remembered stimulus is attracted toward two distinct distorting factors. One is a task-irrelevant stimulus seen on the same trial, which we hypothesize to operate on early visual processing through perceptual averaging. The second is the prototypical stimulus with the average value of all previously seen stimuli, which is proposed to impact stored memory presentation. Finally, in the third study, I recorded subjects' EEG while they performed a task similar to the second study's. I found that the fluctuation of selective attention, reflected by the amplitude of alpha oscillations (8--14 Hz), is strongly predictive of the degree to which memory recall is distorted by the prototypical stimulus. It suggests that the influence of the prototypical stimulus is an adaptive and compensatory response to visual memory's imprecision. Taken together, these studies further our understandings to visual memory and provide a basis for future explorations.