A Model of Perceptual Task Eﬀort for Bar Charts and its Role in Recognizing Intention Stephanie Elzer (elzer@cs.millersville.edu) Dept of Computer Science, Millersville Univ., Millersville, PA 17551 USA Nancy Green (nlgreen@uncg.edu) Dept of Mathematical Sciences, Univ. of North Carolina at Greensboro, Greensboro, NC 27402, USA Sandra Carberry (carberry@cis.udel.edu) Dept of Computer Science, Univ. of Delaware, Newark, DE 19716 USA James Hoﬀman (hoffman@udel.edu) Dept of Psychology, University of Delaware, Newark, DE 19716 USA October 27, 2005 Abstract. This paper presents a model of perceptual task eﬀort for use in hypothesizing the message that a bar chart is intended to convey. It presents our rules, based on research by cognitive psychologists, for estimating perceptual task eﬀort, and discusses the results of an eye tracking experiment that demonstrates the validity of our model. These rules comprise a model that captures the relative diﬃculty that a viewer would have performing one perceptual task versus another on a speciﬁc bar chart. The paper outlines the role of our model of relative perceptual task eﬀort in recognizing the intended message of an information graphic. Potential applications of this work include using this message to provide 1) a more complete representation of the content of the document to be used for searching and indexing in digital libraries, and 2) alternative access to the information graphic for visually impaired users or users of low-bandwidth environments. Keywords: perceptual eﬀort, cognitive modeling, diagrams, plan recognition c  2006 Kluwer Academic Publishers. Printed in the Netherlands. UMJ-final.tex; 3/02/2006; 9:43; p.1