Abstract

Measurements of subjects' eye and head movements during the block-copying task led to the observation that some subjects executed independent eye and head movements, dissociating their spatial and temporal trajectories, an observation inconsistent with current models of eye and head movements that postulate a common gaze shift goal. In another series of experiments, subjects performed the block-copying task while performing one of two secondary tasks. The added cognitive load led to dramatic changes in subjects' head trajectories, and affected the strategies subjects used in constructing the duplicate pattern.

The experiments provide support for a different approach to studying visual processing, in which vision is viewed as more top-down than previously supposed. The task takes on particular importance, because behavior cannot be divorced from the immediate task(s). Fixations are shown to play crucial cognitive roles in perception, including binding task-relevant information to variables in working memory, and indexing the execution of sequential programs.

Table of Contents

• Chapter 1. Introduction

• Chapter 2. The Block Copying Paradigm

  • Introduction
  • Methods
    • Monitoring eye position
    • Monitoring head and hand position
  • Procedure
    • Scoring of block-move strategies
  • Results
    • Basic Features of Task Performance
      • Relative Frequency of Strategies
      • Change in Strategy Use Over the Eight-Block Trial
      • Number of References to the Model per Block Copied
      • Trial Duration
      • Fixation Durations in Model Area
  • Discussion

• Chapter 3. Tradeoff between frequent eye movements and working memory load

  • Introduction
  • Manipulating Task Parameters
    • Increasing the Cost of Frequent Model References
    • Manipulating the Information Content of the Model
      • The Monochrome Condition: Eliminating Color Information
      • The Linear Condition: Reducing Position Information
  • Discussion

• Chapter 4. The Coordination of Eye, Head, & Hand Movements in a Natural Task

  • Introduction
  • Basic features of eye, head, and hand movements:
    • Correlation of Eye, Head, and Hand Movements
    • Amplitude of Head Movements
    • The Coordination of Eye and Head Movements in Gaze Changes
  • Discussion

• Chapter 5. The Effect of a Concurrent Cognitive Load on Task Performance

  • Introduction
  • The Dual-Task Paradigm
  • Concurrent Cognitive Load
    • The"Attend" Condition
    • The"Say Other Color" Condition
  • Results
    • Effects on motor coordination:
    • Effects on Eye Movement Strategies
    • Number of Model References Per Block
    • Concurrent Cognitive Load in the 'Far' Condition
  • Discussion

• Chapter 6. General Discussion

• Bibliography

• Appendix

Curriculum Vitae

The author was born in Palo Alto, California on March 25, 1956, and grew up in Ann Arbor, Michigan. He attended the Rochester Institute of Technology, earning a Bachelor of Fine Arts degree in Fine Arts Photography in 1980 and a Masters of Science in Imaging Science in 1986. He began his studies at the University of Rochester in the fall of 1990 at the Center for Visual Science. He pursued his research under the direction of Professor Hayhoe, and received his Master of Arts degree in 1993. He is currently on the faculty of the Center for Imaging Science at the Rochester Institute of Technology.

Acknowledgments

A great many people contributed, directly and indirectly, to the body of work that makes up this dissertation. The guidance and encouragement provided by Mary Hayhoe and Dana Ballard were invaluable. Discussions with Steven Shimozaki, Keith Karn, Per Möeller, and Michael Spivey also helped shape the experiments. Early work by Mary Hayhoe, Dana Ballard, Steven Whitehead and Feng Li provided the base on which this work was built. The work was only possible because Alan Russell, Andrew Forsberg, Deborah Bancroft, and Timothy Becker shared their ideas and skills so generously. Portions of the work represented in this thesis have been supported by NIH RO1 EY05729, NIH R24 RR06853, and AFOSR-91-0332. Additional support was received from the Rochester Institute of Technology's Center for Imaging Science Industrial Associates Program. Finally, the whole experience could never have taken place without the love, support and patience of Myra, Rachel, and Madeline Pelz.