Analysing uncertainty in location memory: issues in the design of spatial database systems

Abstract

SUMMARYFuture generations of databases will store increasing amounts of pictorial and other visuospatial material. Among other methods, these will require retrieval techniques which exploit memory for the location of objects in pictures stored within the database. Experiments are reported in which subjects recalled the location of an object in a picture and, as an expression of their uncertainty, a range of locations within which they were sure the target fell. This is analogous to a database query method in which users specify a range of values for a location as a means of overcoming the unavoidable problem of imprecision in the expression of an analogue quantity. This paper investigates the psychological issues which allow us access to the potential value of this method in the design of pictorial databases. Although recall con®dence (de®ned by the width of the range of responses given by the subject) is shown to be correlated with recall accuracy, the results demonstrate a trend in which subjects systematically overestimate the precision of their recall. A further experiment examines the extent to which this eect can be manipulated by instructions to the subjects. This shows that instructions aimed at reducing overcon®dence produce a counterintuitive response. Subjects remain spuriously overcon®dent about the accuracy of responses which are in fact incorrect, but additionally they demonstrate a reduced con®dence for accurate recalls. Overall, these experiments indicate that while con®dence ranges can communicate useful information about the accuracy of location memory, this is less than that expected because subjects are poor at assessing the accuracy of their own recalls and are subject to a range of biases when attempting to do so. Implications for the design of retrieval systems are discussed.