No significant differences were observed in the psychometric measures, between the two age groups. Since some of these measures purportedly reflected WM efficiency (the digit span forward; digit span backward; spatial span forward; and spatial span backward), this suggests these psychometric measures are relatively insensitive to the AST effects on aging. This result has been found previously. Surprisingly in the Eenshuistra et al. (2004) experiment reported earlier, conclusions were drawn in favor of a deterioration of WM as the key source of age-related AST impairments, under the assumption that WM deficits among older participants may only noticeably affect cognitive task performance under conditions of competing task responses (e.g., Roberts et al., 1994). Thus, the WM measures derived from the AST conditions of the various tasks may be more sensitive to subtle age-related cognitive changes in healthy adults.