Understanding: a function of short-term memory?
We describe our investigations of the sentence comprehension abilities of 2 patients with a severe impairment in their auditory verbal short-term memory (conduction aphasia). Both were capable of comprehending a range of sentences, even when adequate comprehension was dependent upon the processing of order-dependent syntactic information rather than the utilization of semantic knowledge. Thus they performed satisfactorily on tests using plausibly reversible subject and object constituents with either active or passive verb phrases or prepositional phrases. Both, however, were impaired on sentences which departed from normal conversational conventions in terms of their reference to the order of event occurrence, or to the subject and object of an array. They were also very poor at performing comparative judgements, even when these involved a simple intrinsic attribute such as colour. These findings are discussed in terms of the role of auditory verbal short-term memory in backing up and back-tracking over spoken information when conditions preclude the immediate understanding of auditory-verbal information.