Divided attention effects on retrieval from episodic memory

grantor: University of TorontoIn this thesis the dual-task technique is used to infer the component processes involved in episodic memory retrieval. In each of the six experiments, participants studied a list of random words under full attention, and recalled them while performing a distracting task presented visually on a computer. Previous research suggested that divided attention (DA) during retrieval disrupts free recall for words if the distracting task also involves memory for verbal material (Fernandes & Moscovitch, 2000). The purpose of the present work was to determine more precisely which factor(s) modulated this effect, and influence retrieval success. In the first experiment I found that verbal distracting tasks, that required animacy or syllable decisions to words, produced large interference on memory. Experiments 2 and 3 showed that phonemic decisions about nonsense-words produced a similarly large interference effect on memory, that was larger than semantic decisions or size-estimations about pictures of objects. These findings support the component-process model of memory, which suggests that retrieval is largely disrupted only when there is competition for a common representational system. In the next set of experiments an alternative, reduced-resource, account of interference from DA at retrieval is considered by comparing the performance of young and old adults under DA conditions. A word-animacy distracting task interfered substantially with retrieval, but the size of the effect was not amplified in old compared to young adults. Dividing attention using an odd-digit task did not produce as large an effect, in either group. Finally, the contribution of the frontal and temporal lobes to interference effects on memory were examined. Elderly participants were divided pre-experimentally into 4 groups, determined by their scores on measures of frontal and temporal lobe function, derived from neuropsychological testing. Large interference effects on memory were produced by the animacy, but not the odd-digit distracting task. The pattern and magnitude of interference effects did not differ depending on level of temporal or frontal function. These results do not support the hypothesis that effects of DA at retrieval are due to a reduction in general processing resources, attentional capacity, or competition for memory structures in the temporal lobe.Ph.D