Mr. Chips: An ideal-observer model of reading

Gordon E. Legge, Timothy S. Klitz, Bosco S. Tjan
1997 Psychological review  
The integration of visual, lexical, and oculomotor information is a critical part of reading. Mr. Chips is an ideal-observer model that combines these sources of information optimally to read simple texts in the minimum number of saccades. In the model, the concept of the visual span (the number of letters that can be identified in a single fixation) plays a key, unifying role. The behavior of the model provides a computational framework for reexamining the literature on human reading saccades.
more » ... n reading saccades. Emergent properties of the model, such as regressive saccades and an optimal-viewing position, suggest new interpretations of human behavior. Because Mr. Chip's "retina" can have any (onedimensional) arrangement of high-resolution regions and scotomas, the model can simulate common visual disorders. Surprising saccade strategies are linked to the pattern of scotomas. For example, Mr. Chips sometimes plans a saccade that places a decisive letter in a scotoma. This article provides the first quantitative model of the effects of scotomas on reading. Reading and Vision A critical part of normal reading is the integration of visual data with lexical knowledge and eye-movement control. This integration process is the central computational problem addressed in this article. Mr. Chips is a computer program that implements an ideal-observer principle for this integration. Damage to the early visual pathways can disrupt reading. More than 3 million Americans have low vision, defined as a visual disability, not correctable by glasses or contact lenses, that has an impact on daily function. 1 Most people with low vision have reading difficulties. A major goal of this article is to present a theoretical analysis of the role of vision in reading that encompasses both normal and low vision. In a series of psychophysical studies, Legge and colleagues have investigated the effects on reading of many physical param-
doi:10.1037/0033-295x.104.3.524 pmid:9243963 fatcat:3rtn27dpc5f7do4qxzsw6o6gm4