eye movements made when only looking are different from those made when tapping. Visual search functions as a separate process, incorporated into both tasks: it can be used to improve performance when memory load is heavy.

Gaze-shift dynamics of unrestrained seated subjects were examined. The subjects participated in two tasks. In the first task, they tapped sequences of 3-D targets located on a table in front of them. In the second task, they only looked at similar sequences of targets. The purpose of the task (tapping vs only looking) affected the dynamics of gaze-shifts. Gaze and eye-in-head peak velocities were higher and gaze-shift durations were shorter during tapping than during looking-only. We conclude that task variables affect gaze-shift dynamics, altering characteristics of the so-called saccadic "main sequence".

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The Oculomotor Geometry Reasoning Engine (OGRE) was proposed to model eye movements and visual working memory during problem solving in geometry. OGRE postulates that geometrical elements from diagrams are added to visual working memory when they are scanned. Newly-added elements overwrite elements already in memory. The model was applied to eye-movement patterns of three subjects: two geometry experts and one non-expert. Their eye movements and verbal protocols were recorded as they solved geometry problems posed with diagrams. Subjects used highly redundant eye-movement patterns with multiple rescans of the same geometrical elements. OGRE's model of visual memory provided a good fit for the distribution of times between rescans. The model was used to estimate the size of visual working memory used in geometry. The estimates varied as a function of both problems and subjects, with means and standard deviations for each subject being: 5.3+/-1.4, 4.0+/-0.9 and 4.7+/-1.6.

Current theories of reading eye movements claim that reading saccades are programmed primarily on the basis of information about the length of the upcoming word, determined by low-level visual processes that detect spaces to the right of fixation. Many studies attempted to test this claim by filling spaces between words with various non-space symbols (fillers). This manipulation, however, confounds the effect of inserting extraneous characters into text with the effect of obscuring word boundaries by filling spaces. We performed the control conditions necessary to unconfound these effects. Skilled readers read continuous stories aloud and silently. Three factors were varied: (i) position of the fillers in the text (at the beginning, the end, or surrounding each word); (ii) the presence or absence of spaces in the text; and (iii) the effect of the type of filler on word recognition (from greatest effect to least effect: Latin letters, Greek letters, digits and shaded boxes). The effect of fillers on reading depended more on the type of filler than on the presence of spaces. The greater effect the fillers had on word recognition, the more they showed reading. Surrounding each word with digits or Greek letters slowed reading as much as filling spaces with these symbols. Surrounding each word with randomly chosen letters, while preserving spaces, slowed reading by 44-75%--as much as, or more than, removing spaces from normal text. Removing spaces from text with Latin-letter fillers slowed reading by only 10-20% more. We conclude that fillers in text disrupt reading by affecting word recognition directly, without necessarily affecting the eye movement pattern.