Convenient fixation location within isolated words of different length and structure.

When a word is visually presented in a naming or comparison task in such a way that the eye is initially fixated at different locations within the word, a very strong effect of fixation location is found. The effect appears as a U-shaped curve. Naming time and total fixation time (gaze duration) have a minimum for an initial fixation location between the third and fifth letter of the word (for words that are 5-11 letters long). When initial fixation location deviates from this optimum position, times increase at the surprisingly fast rate of 20-30 ms per letter of deviation. By manipulating the internal lexical structure of the words, we show that at least part of the fixation location effect is caused by mechanisms related to ongoing lexical processing. This is demonstrated by the fact that the fixation location effect takes a different form when the most informative part of a word (as determined by dictionary counts) occurs at the beginning or the end of the word.

Integrating visual information from successive fixations: does trans-saccadic fusion exist?

It has recently been suggested that there exists a level i the nervous system where a kind of photographic representation of our visual environment is constructed from "snapshots" taken by successive eye fixations. An experiment is presented that argues against this view, and an alternative explanation is put forward to explain why we see the environment as being stable and continuous despite eye movements.

Sensory factors are insufficient to define the ocular saccade goal in complex visual fields.

In most normal visual search situations, the environment is filled with a variety of stimuli, and selection among possible saccade targets is necessary. Current theories of visuomotor mechanisms must take into account not only the classical 'retinal error' input signal, but also perceptual and decisional factors as well as task-specific strategies adopted by the subjects. Experiments are reported in which eye movements are recorded in tasks requiring ocular saccades to be made onto target letters indicated by a peripherally visible mark or embedded within lines of homogeneous background letters. The results show how nonsensory factors interact with visual determinants in the preparation of the exploratory saccades. Expectations concerning the visibility of the sought-for target influence the spatial and temporal parameters of the eye movement which will be executed.