suppression:Memory for verbal material is impaired when people are asked to say something irrelevant aloud. This is assumed to block the articulatory rehearsal process, leading memory traces in the phonological loop to decay. Transfer of information between codes:With visually presented items, adults usually name and sub-vocally rehearse them, so the information is transferred from a visual to an auditory encoding. Articulatory suppression prevents this transfer, and in that case the above-mentioned effect of phonological similarity is erased for visually presented items. Neuropsychological evidence:A defective phonological store explains the behavior of patients with a specific deficit in phonological short-term memory. Aphasic patients with developmental verbal dyspraxia are unable to set up the speech motor codes necessary for articulation, caused by a deficiency of the articulatory rehearsal process. On the other hand, patients with dysarthria, whose speech problems are secondary, show a normal capacity for rehearsal. This suggests that it is the subvocal rehearsing that is crucial. Evidence in support of a phonological short-term store An accumulation of literature across decades has lent strong support to the theory of phonological STS. In a 1971 study, Stephen Madigan demonstrated that a larger recency effect is seen during forward serial recall when people are presented a list auditorally as opposed to visually. (A smaller effect is seen in backwards serial recall.) In his study, auditory presentation led to greater recall of the most recently studied items. Catherine Penney expanded on this discovery to observe that modality effects can also be found in the case of free recall tasks. In 1965, Dallett had discovered that this observed modality effect is greatly reduced by the addition of a "suffix" item to the presented list; this suffix is a distractor item that is not to be recalled. Robert Greene utilized this observation in 1987 to discover that this suffix effect has a larger impact on lists learned auditorally as opposed to visually. The culmination of all of these findings results in strong support of the theory that there is a short-term store that phonologically stores recently learned items. In addition, Bloom and Watkins found that the suffix effect is greatly diminished when the suffix is not interpreted as linguistic sound, which agrees with the phonological short term store theory as it would be largely unaffected by non-linguistic distractors. Visuo-spatial working memory Alan Baddeley's theory of working memory has yet another aspect to which memory can be stored