The role of attention during retrieval in working-memory span: a dual-task study. 
We tested the hypothesis that retrieving target words in operation span (OSpan) involves attention-demanding processes.  Participants completed the standard OSpan task and a modified version in which all equations preceded all target words.  Recall took place under either full attention or easy versus hard divided-attention conditions.  Recall suffered under divided attention with the recall decrement being greater for the hard secondary task.  Moreover, secondary-task performance was disrupted more by the standard OSpan task than by the modified version with the hard secondary task showing the larger decrement.  Finally, the time taken to start recalling the first word was considerably longer for the standard version than for the modified version.  These results are consistent with the proposal that successful OSpan task performance in part involves the attention-demanding retrieval of targets from long-term memory.