Are forwards and backwards digit recall the same? A dual task study of digit recall

There is some debate surrounding the cognitive resources underlying backwards digit recall. Some researchers consider it to differ from forwards digit recall due to the involvement of executive control, while others suggest that backwards recall involves visuo-spatial resources. Five experiments therefore investigated the role of executive-attentional and visuo-spatial resources in both forwards and backwards digit recall. In the first, participants completed visuo-spatial 0-back and 2-back tasks during the encoding of information to be remembered. The concurrent tasks did not differentially disrupt performance on backwards digit recall relative to forwards digit recall. Experiment 2 shifted concurrent load to the recall phase instead, and in this case revealed a larger effect of both tasks on backwards recall relative to forwards recall, suggesting that backwards recall may draw on additional resources during the recall phase and that these resources are visuo-spatial in nature. Experiments 3 and 4 then further investigated the role of visual processes in forwards and backwards recall using dynamic visual noise (DVN). In Experiment 3 DVN was presented during encoding of information to be remembered, and had no effect upon performance. However, in Experiment 4 it was presented during the recall phase, and the results provided evidence of a role for visual imagery in backwards digit recall. These results were replicated in Experiment 5 in which the same list length was used for forwards and backwards recall tasks. The findings are discussed in terms of both theoretical and practical implications.