A computer-based microworld for the assessment and remediation of sentence processing deficits in aphasia
This thesis investigates impairments of written sentence comprehension in 14 aphasic adults. The primary purpose of the research was to apply computer technology to the process of assessment, with the aim of improving diagnostic precision and thereby being able to offer better-targeted and more effective treatment. To facilitate the study of sentence processing disorders a microworld was developed, populated solely by animate and inanimate balls, boxes and stars. This medium had two major advantages over natural English. Firstly, the restricted vocabulary and the small set of grammatical structures used permitted finer control of the linguistic environment, and secondly, all the test sentences were fully reversible with equal plausibility. The microworld formed the basis for a suite of patient-controlled computer programs dedicated to the study of two functions: the processing of verbs and the processing of locative prepositions. Computerisation enabled automatic, detailed and objective data collection in assessment mode, freeing the observing clinician to make important complementary observations. In remediation mode the software externalised the subtasks of sentence comprehension for clinical study. The results of an efficacy study are reported in which the aphasic subjects were divided into two groups of seven and subjected to a cross-over design experiment. Group A received verb treatment before preposition treatment and Group B received the treatments in opposite order. Significant treatment effects were obtained which could be attributed confidently to the intervention applied and which included generalisation to 'real world' reading tasks. Many of the subjects maintained benefit of treatment after a non-treatment interval of five months. The thesis presents a range of new data on aphasic performances including details of error patterns, response latencies and susceptibility of the different sentence structures to treatment. In addition the aphasics are compared with 45 normal subjects in their computer interface operation and on a new six-module Syntax Screening Test. Theoretical contributions to knowledge are made in the establishment of the dissociability of verb and preposition processing and in the interpretation of the clinical observations. The microworld and software created have potential application in many other areas of language research.