The reliability of the Functional Assessment Measure (FIM+FAM) is an important issue with its increased use in the measurement of neurological disability and rehabilitation outcome. Although the Motor items have good reliability ratings, the Cognitive items are more difficult to complete and their reliability is not as good. This study tests the suggestion that this might be due to the Cognitive items being more abstract. A keyword from each of four Motor items was compared with a keyword from four Cognitive items. Abstractness was measured by measuring the 'imageability' of each keyword. The Motor items were found to have a significantly higher mean imageability rating than the Cognitive items. Thus, there is support for the suggestion that abstractness contributes to the poorer reliability of the Cognitive items. These results led to the proposal that the reliability of the Cognitive items might be improved by various methods of increasing the tangibility of these measures (e.g. subdivision of broad categories of disabilities, enhancing item descriptions, training raters to increase their recognition of relevant observations, and using specific assessment tasks to elicit relevant behaviours).