The simple tapping in synchronization with the irrelevant speech sound did not decrease the performance of serial recall and did not affect the magnitude of the phonological similarity effect. Similarly, Saito (1993a) showed that a simple tapping task with computer-produced tone did not affect the phonological similarity effect.
Saito (1993b, Expt 2) investigated the effects of memory updating, a method used by Morris & Jones (1990), on the phonological similarity effect. Although memory updating is an attention demanding process that elicited a deterioration in memory performance, the phonological similarity effects still existed in the updating conditions.
The phonological similarity effect appeared in the control condition.
On the other hand, the intermittent suppression task requires participants to utter segmentally 'ah, ah, ah...' and that is enough to ensure that the phonological loop is pre-empted to the extent that the phonological similarity effect disappears.
On the other hand, repeated production of a single vowel 'ah' is sufficient to abolish the phonological similarity effect (Expts 1 and 2), and Murray (1968) showed a similar effect with a single syllable 'the'.
Bishop & Robson (1989) observed the phonological similarity effect and the word-length effect in children with no articulate speech from birth and it is difficult to accept that such children have developed an adequate speech motor programme without ever having produced overt speech.
Influence of articulatory suppression and memory updating on phonological similarity effect. Japanese Journal of Psychology, 64, 289-295.
What effect can rhythmic finger tapping have on the phonological similarity effect? Memory and Cognition, 22, 181-187.