2005): Time course of information processing during scene perception: The relationship between saccade amplitude and fixation duration, Visual Cognition, 12:3, 473-494

ABSTRACT:For a development of truly user-centered interfaces we need to take into account not only generic characteristics of human beings but also actual dynamics of attention and intentions of persons involved in an interaction. Modem eyetracking methods are indispensable tools in such a development, as they allow the use of eye movement data for control of output devices, for gaze-contingent image processing and for desambiguation of verbal as well as nonverbal information. The main obstacle on the way to these applications is the so-called "Midas touch problem": how to differentiate "attentive" saccades with intended goal of communication from the lower level eye movements that are just random or provoked by external stimulation? We report results of our investigations of the problem and present a solution based on a functional classification of fixations correlated with their duration. Several additional solutions are also considered together with the data on the trainability of the human oculomotor system.

Presenting a distractor prolongs not only saccadic reaction times in paced tasks but also fixation durations in unpaced tasks. To investigate whether the effect of a distractor is a pure optomotor reflex, we used both visual and auditory distractors in an unpaced picture-viewing paradigm. Results show a distractor effect for both modalities. Analysis of data from previous studies showed similar effects, even in amodal shifts of attention. These findings challenge the hypothesis that the effect is modality-specific and suggest that the distractor effect may be another expression of the orienting reflex.

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A display gain setting defines the mapping of a movement to the real-time visual display. In two experiments we investigated how the acquired adaptation to low and high display gain affected motor control of single aimed stylus movements. Experiments differed with respect to how gain was varied. In Experiment 1, gain was realized by manipulating the surface displacements with a constant display. The results show an expected linear decrease of movement time and spatial accuracy, which is in sharp contrast with the often-reported U-shaped relation. Experiment 2 was run to study the influence of visual feedback in low- and high-gain conditions. The manipulation of gain was realized by display variation with unaltered surface displacements. The linear increase of movement time and feedback processing with gain and the unaltered spatial accuracy across conditions, suggested that participants actively adapted to the displayed visual information in altered gain conditions.