Evidence to support independence of PL and VSSP

Question 1

Evidence that A&S Unitary model of STM is wrong

Answer 1

Shallice & Warrington, 1970 - Patient KF showed deficits in digit span with intact memory for images. A&S model is oversimplified.

Question 2

Phonological Similarity Effect - Evidence for PL independence

Answer 2

Conrad & Hull 1964 - When recalling letter strings, those that are phonologically similar are harder to recall than those that are phonologically distinct. Showing verbal info is coded phonologically, not visually.

Question 3

Unattended speech effect - Evidence for PL independence

Answer 3

Baddeley - Performance on span tasks is impaired if items are accompanied by other (unattended) verbal material - both unrelated spoken words/ spoken digits/ similar phonemes all affected digit span to similar effect. Showing the coding of verbal info is phonemic and not semantic.

Question 4

PV - Evidence for PL independence

Answer 4

Vallar - Patient PV exhibited seriously impaired PL function (no other problems) - Shown isolation of PL. She exhibited no phonological similarity effect or word length effect.

Question 5

KF - Evidence for VSSP autonomy

Answer 5

Shallice & Warrington via KF that has verbal deficits with intact memory for images. However single dissociation only. He exhibited better remembrance in corsi block tapping task than he did for digit recall.

Question 6

Evidence From Dual Task Paradigm - 2 tasks can be simultaneously performed only if they don’t require the same functions -

Answer 6

Articulation of irrelevant items dominates ACP (Articulatory suppression) = verbal memory task is hard / where as VSSP task is easy/unaffected (corsi block span) - CONVERSELY - Brooks matrix task (subjects told to imagine a 4x4 grid subjects learn sequence of sentences spatial instructional or nonsense instructional) - the subjects remembered more spatial sentences than non-spatial. Baddley made subjects perform the brooks matrix task with concurrent task that was designed to disrupt spatial STM - Found this disrupted initial BMT results but not non-spatial equivalent. Suggests separate VSSP and Verbal Processes.

Question 7

PET Scanning

Answer 7

Smith 1996 - Pet scanning suggests different neural basis for visual and verbal retention in intact pps.

Question 8

Hemisphere differences

Answer 8

DeRenzi 1975 - Left hemisphere patients had impaired digit span, but ok spatial span, While right hemisphere patients had impaired corsi block span, but ok digit span.

Question 9

Down’s syndrome and Wikinson’s syndrome exhibit different abilities

Answer 9

Wang 1994 - Those with Wilkison syndrome were impaired at spatial task but not verbal – those with down’s were impaired at verbal and not spatial – indicating neurological underpins underlying the independence of the two features.

Question 10

HOWEVER - Evidence that the two systems interact.

Answer 10

Baddeley 2000 - small detectable visual similarity effect in verbal recall showing words are both phonemically and visually coded - However this is explained in Baddeley’s update of WM model with the inclusion of the episodic buffer.