ABSTRACT
This chapter describes an eye movement recording device presently in use and the construction of a computer algorithm which defines a fixation. Also, it underlines the importance of researchers reporting their fixation criteria, examples are provided of how subtle changes in some fixation criteria may dramatically affect the processed fixation data output. Video recording devices are limited to a sampling rate of 60 per second, which is too slow to measure either the short voluntary eye jumps (saccades) between fixations or the more rapid involuntary eye movements that occur during a fixation. Other recording devices are more suitable for measuring eye motion per se, but our interest is in measuring fixation positions and their time history. In general, all researchers must arrive at a data partitioning scheme custom tailored to their own specific needs. However, the summary measures of fixation frequency, duration, and location generated by any particular algorithm are quite common and likely to be taken for granted.
