Determining spatial span: The role of movement time and articulation rate

In studies of verbal memory span individual differences in speech rate have been found to predict the number of items that can be recalled in order. This is thought to happen because overt speech rate is related to the rate of internal verbal rehearsal. For spatial span there may also be an internal rehearsal system linked to overt responding, and if there is a strong analogy to be drawn between the verbal and spatial domains, then movement time between spatial targets should predict the number of spatial locations that can be recalled. In the first study reported, none of the six measures of movement time did predict spatial span, but, as expected, speech rate predicted verbal span. In addition, speech rate predicted spatial span. In a second study the use of articulatory suppression during span presentation showed that verbal span dropped, but was still predicted by speech rate. Spatial span was again predicted by the time it took to say digits rather than the time it took to make movements to spatial targets. There would not seem to be any simple analogy between the limitations on verbal span and those on spatial span. In addition, the relationship between speech rate and sequential memory performance may be more complex than previous studies have suggested.