Suppression and Interference Control in Memory Retrieval
K. W. Joan Ngo · TSpace (University of Toronto) · 2019
Resolving interference from competing information is a critical factor in memory retrieval. This thesis investigated suppression as the inhibitory mechanism required to select target information among competitors, by examining the effect of aging and the synchrony between circadian arousal and time of testing during interference resolution. Study 1 demonstrated below-baseline suppression of competitors by young adults using a novel paradigm that induced interference based on semantic associations, and showed that the magnitude of suppression was correlated with individual working memory span. Study 2 found no evidence of suppression by older adults, supporting the theory that older adults’ memory deficits are related to impaired inhibitory control. Study 3 tested whether the ability to suppress competing memory traces varies with the synchrony between optimal arousal period and time of testing. Using a variant of the paradigm developed in Study 1, the below-baseline suppression effect for young adults tested at optimal times of day was replicated, and participants tested at non-optimal times of day showed facilitation of competitors instead. Study 4 investigated whether optimal time testing would improve older adults’ inhibitory control to reduce interference. Study 4 did not find evidence of below-baseline suppression for older adults at either testing period, however, older adults demonstrated a facilitation effect at non-optimal times of day similar to that shown by younger adults in Study 3. Lastly, Study 5 aimed to supplement this line of research with electrophysiological evidence of differential processing for targets and interfering competitors. Although no behavioral difference in access to competitors was found in Study 5, the neural data demonstrated an ERP signature that may reflect suppression of competing information in interference resolution. Together, these studies converge to show that semantic interference is resolved by inhibitory processes that decrease the accessibility of competitors at retrieval for young adults, but not older adults.