Processing Strategy And Individual Differences In Working Memory:ERPs Studies

Individual difference in working memory capacity is a hot topic. The results from behavior studies have revealed two essential factors lead to individual differences in working memory. There are executive attention and processing strategy. Executive attention theory and strategy differences hypothesis interpret the influence of two factors to individual differences in working memory, respectively. Executive attention theory suggests executive attention is the key capacity in working memory. Executive attention and working memory capacity have a direct relationship. Compared with low working memory capacity individuals (short for low WMC), high working memory capacity individuals (short for high WMC) have stronger executive attention. Therefore, high WMC individuals can focus attention on targets easily and eliminate distractors. However, strategy differences hypothesis suggests the essential difference of working memory capacity is utility of strategy in task. Compared with low WMC individuals, high WMC individuals are more effective to learn and use processing strategy, such as encoding and rehearsal strategy.Although results from behavior studies support both of executive attention theory and strategy differences hypothesis, a great many achievements of cognitive neuroscience support the executive attention theory only and few results support strategy differences hypothesis. One of the possible reasons is most of researches in cognitive neuroscience adopt high-interference remember and ignore paradigm. In these tasks, subjects are instructed to remember targets and ignore distractors. This artificial interfering environment may evoke excessive executive attention of subjects to eliminate distractors, as a result, reducing utility of other capacity, such as processing strategy. We are interested in, If let subjects perform the low-or none-interference tasks, and subjects put into few executive attention, then what neurological differences can be reflected between high and low WMC individuals?To address this and find further evidences to support strategy differences hypothesis, we design two ERP studies which containing low-or none-interference tasks. Experiment1and2are two factors mixed designs. Between-subject factor is high and low WMC groups. We used measurement methods consisting with previous studies to divide subjects into two groups. The within-subject factor in experiment1contains two levels, high-and low-interference tasks. In high-interference condition, there are three unmeaning items which presenting in line at central screen. The central item is different with the other two items surrounding it, but the surrounding items are the same. The subjects are instructed to remember the central item. In low-interference condition, the three items are the same. The within-subject factor in experiment2also contains two conditions, memory maintenance and manipulation tasks. The two tasks are typical working memory task. Maintaining and manipulating stimuli are nameable items, such as triangle.The results revealed, in experiment1, compared with performing high-interference task, when performed low-interference task, the high WMC group paid more attention on targets, which suggested in low-interference task, the high WMC group adopted flexible encoding strategy, such as bonding memory strategy, rather than stronger executive attention to encode and remember bonding targets. However, when the low WMC group performed high-and low-interference tasks, the activity of attention in two tasks are not significant differences. The results suggested as the same with the performance in high-interference task, in low-interference task, the surrounding distractors decentralized attention of low WMC subjects (even the targets and distractors are the same) and reduce the encoding of targets. The results revealed in memory encoding period, the high and low WMC groups may adopt different encoding strategy. The results in experiment2revealed in memory representation and rehearsal period, the high and low WMC subjects also adopted different representation and rehearsal strategy to complete tasks. When performed visual maintenance and manipulation task, the high WMC subjects used superior image representation or rehearsal method to process task compared with the low WMC subjects adopting mismatching non-visual representation or rehearsal method. The results of experiment2revealed the high WMC group rather than the low WMC group use optimized representation and rehearsal strategy effectively.The experiment1and2find evidences of neuroscience to support the strategy difference hypothesis. The evidences are, in memory encoding and representation/rehearsal period, the high and low WMC individuals are differences in utility of strategy. Combine with previous studies, we infer, both of executive attention and utility of strategy in task are the factors to lead to individual differences in working memory capacity.