As technical information becomes a vital part of technology, information displays such as the chart in this preliminary study will play increasingly important roles. Especially in light of the proliferation of graphics software, continued research into the workings of information displays is relevant and timely. Julesz' notion of "preattentive vision" suggests that humans may process visual information efficiently because all of the perceptual elements of a display can be processed simultaneously. Cleveland and McGill have isolated out a hierarchy of perceptual tasks that provide a framework for evaluating specific components of information displays. This preliminary study suggests Cleveland and McGill's theory as valuable and informative. Our results do not claim to confirm or disconfirm Cleveland and McGill. Further studies which focus on this theory, and on other combinations of tasks, are vital to our field and will continue to increase our knowledge of how information displays work. This knowledge will play an important role for technical communication practitioners in the future. Finally, two points are important with regard to this and other studies in visual and technical communication. First, it should be noted that our study used college students as subjects. It would be interesting to study a more diverse subject population, especially one that including working professionals and other end-users of technical documents. Second, although there is a need for better theory and guidelines about visual communication, caution should be taken when attempting to generalize from any study. Results based on isolating one or two visual elements may not be generalizable across a situation that is diverse in terms of its communication media and its user groups. Nonetheless, continued empirical studies from a variety of disciplines are important for building theory about the visual communication of technical material.