Human sensitivity to variability information in detection decisions

Three studies investigated the ability of observers to extract and use reliability information from graphical elements presented on a visual display. The first experiment assessed observers' accuracy in detecting differences in source reliability based on differences in the temporal variability of the sources. Observers' accuracy improved as the sample size and the difference in the underlying source variability increased. The second study investigated observers' efficiency in using the information about source variability to weight individual sources in forming a decision. Observers were able to differentially weight sources based on the underlying source variability. However, observers' adjustments of the weights tended to be less than ideal, particularly when reliable sources were not spatially contiguous and additional aids (e.g., observation periods and highlights) were unavailable to help observers identify differences in source variability. Finally, evidence in the third study indicated that information about differences in source variability reduced uncertainty about the locations of reliable sources but did not help observers to correctly adjust weights to match the ideal. In application, display enhancements (e.g., highlights) aid decision making when only general differences in reliability need to be recognized, but more advanced decision support is recommended when reliability information has to be incorporated into a decision statistic.