Title: Temporal andspatial aspects of eye-movement control : from reading toscanning
Abstract: Eye movements are a powerful tool to
examine cognitive processes. However, in most paradigms little is
known about the dynamics present in sequences of saccades and
fixations. In particular, the control of fixation durations has
been widely neglected in most tasks. As a notable exception, both
spatial and temporal aspects of eye-movement control have been
thoroughly investigated during reading. There, the scientific
discourse was dominated by three controversies, (i), the role of
oculomotor vs. cognitive processing on eye-movement control, (ii)
the serial vs. parallel processing of words, and, (iii), the
control of fixation durations. The main purpose of this thesis was
to investigate eye movements in tasks that require sequences of
fixations and saccades. While reading phenomena served as a
starting point, we examined eye guidance in non-reading tasks with
the aim to identify general principles of eye-movement control. In
addition, the investigation of eye movements in non-reading tasks
helped refine our knowledge about eye-movement control during
reading. Our approach included the investigation of eye movements
in non-reading experiments as well as the evaluation and
development of computational models. I present three main results :
First, oculomotor phenomena during reading can also be observed in
non-reading tasks (Chapter 2 & 4). Oculomotor processes
determine the fixation position within an object. The fixation
position, in turn, modulates both the next saccade target and the
current fixation duration. Second, predicitions of eye-movement
models based on sequential attention shifts were falsified (Chapter
3). In fact, our results suggest that distributed processing of
multiple objects forms the basis of eye-movement control. Third,
fixation durations are under asymmetric control (Chapter 4). While
increasing processing demands immediately prolong fixation
durations, decreasing processing demands reduce fixation durations
only with a temporal delay. We propose a computational model ICAT
to account for asymmetric control. In this model, an autonomous
timer initiates saccades after random time intervals independent of
ongoing processing. However, processing demands that are higher
than expected inhibit the execution of the next saccade and,
thereby, prolong the current fixation. On the other hand, lower
processing demands will not affect the duration before the next
saccade is executed. Since the autonomous timer adjusts to expected
processing demands from fixation to fixation, a decrease in
processing demands may lead to a temporally delayed reduction of
fixation durations. In an extended version of ICAT, we evaluated
its performance while simulating both temporal and spatial aspects
of eye-movement control. The eye-movement phenomena investigated in
this thesis have now been observed in a number of different tasks,
which suggests that they represent general principles of eye
guidance. I propose that distributed processing of the visual input
forms the basis of eye-movement control, while fixation durations
are…
Publication Year: 2013
Publication Date: 2013-01-01
Language: en
Type: article
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