Target expansion is a pointing facilitation technique where the user's target, typically an interface widget, is dynamically enlarged to speed pointing in interfaces. However, with densely packed (tiled) arrangements of widgets, interfaces cannot expand all potential targets; they must, instead, predict the user's desired target. As a result, mispredictions will occur which may disrupt the pointing task. In this paper, we present a model describing the cost/benefit of expanding multiple targets using the probability distribution of a given predictor. Using our model, we demonstrate how the model can be used to infer the accuracy required by target prediction techniques. The results of this work are another step toward pointing facilitation techniques that allow users to outperform Fitts' Law in realistic pointing tasks.

Jaime Ruiz and Edward Lank. 2010. Speeding pointing in tiled widgets: understanding the effects of target expansion and misprediction. In Proceedings of the 15th international conference on Intelligent user interfaces (IUI '10). ACM, New York, NY, USA, 229-238.

 author = {Ruiz, Jaime and Lank, Edward},
 title = {Speeding Pointing in Tiled Widgets: Understanding the Effects of Target Expansion and Misprediction},
 booktitle = {Proceedings of the 15th International Conference on Intelligent User Interfaces},
 series = {IUI '10},
 year = {2010},
 isbn = {978-1-60558-515-4},
 location = {Hong Kong, China},
 pages = {229--238},
 numpages = {10},
 url = {},
 doi = {10.1145/1719970.1720002},
 acmid = {1720002},
 publisher = {ACM},
 address = {New York, NY, USA},
 keywords = {Fitts' law, human performance, pointing, target expansion, tiled targets},