Abstract
Three separate studies employed colour tasks to investigate aspects of cognitive impairment in AD. In the first study an information-processing framework was developed using a model of colour processing (Davidoff, 1991, 1997), and the framework guided the design of a number of colour tasks. Contributions of AD and impaired colour vision to task performance were considered, and findings suggested impaired memory and executive functions but relatively intact perceptual functions in AD. Executive functions were the focus of the second study. AD patients are typically impaired on the form sorting component of the Colour-Form Sorting Task (Weigl, 1941) and this impairment was hypothesised to originate from an executive function deficit. The decision-making load of the CFST was varied, and findings suggested that impaired form sorting may originate from a deficit in selective attention to competing stimulus dimensions. The third study was a case study of a 61 year-old woman with visual variant AD who presented with two specific deficits: global processing impairment and inability to name the colour of the ink in the Stroop task. Approaches to the study of selective attention can be divided into two types: holistic and analytic (Shalev & Algom, 2000). The holistic approach was used to investigate her global processing impairment, and the impairment appeared to originate from a feature integration deficit. The analytic approach was used to investigate her Stroop impairment. Findings suggested a deficit in selective attention to competing stimulus dimensions that was perhaps more severe than that shown in standard AD; letter form/colour are for most people separable dimensions, but they appeared integral for her. Participants found the tasks non-anxiety provoking and enjoyable to complete, therefore future research might aim to develop a more comprehensive battery of colour tasks to assess cognitive impairments in AD.