Abstract
This study investigated which of the two, "operating representation" or "identifying representation," causes the representation-based interference forgetting in WM span performances. A letter mental rotation task demanding spatial operations of a verbal representation was employed as the processing task with verbal or spatial memory materials in the WM span tests. If the greater amount of the processing task during retention duration causes decrease only in the spatial memory span, any interference in memory traces should be attributed to the spatial operations of the letter. If it causes decrease in both the verbal and spatial memory spans, any interference in memory traces should be attributed to simple identification of the letter, because it includes both the verbal and spatial representations. Results supported the latter prediction. Therefore, we suggest that interference of processing requirements with memory traces in a WM span test occurs when the representation to be processed is identified.
