Models for letter cancellation performance and their implications for models of reading

Models for letter cancellation are developed, i.e. for tasks where subjects read a coherent piece of prose at the same time as trying to cancel every target letter they encounter. These models have two components (i) a model of how information is represented by the reader, (ii) a model of how this information is scanned to enable the reader to detect particular target letters. Models of representation range from a photographic image of the printed page to a sophisticated multi-level representation, and models of scanning range from a series of independent saccadic movements (like eye movements) to scans which take into account morphemic and syntactic structure.

Several predictions about the detailed pattern of letter cancellation data are developed on the basis of these models, and these are tested on a data base collected by Smith and Groat (1979). While some support for the simpler models is forthcoming, only the most elaborate models (multi-level representation, syntactically guided scan) can fully account for all the data. While instances can be found where the cancellation task is clearly disrupting the reading task, much of the data are consistent with the notion that the letter cancellation task is not excessively intrusive, and our analyses can thus give us significant information about normal reading.