2. The method according to claim 1 wherein the reading scan rate is a line scan rate and determining the line scan rate comprises: processing the movement of at least one eye from the eye tracker to detect line change eye movements by detecting eye movements in a direction opposite from a reading direction of a line or column in the electronic text; determining the user's line scan rate based on detected line change eye movements and a timer, the line scan rate being a numerical value indicative of a number of lines read per unit time; and calculating an estimate of the user's reading speed based on the line scan rate and supplementary scan rate data indicative of the average or actual quantity of electronic text per line.
2. The method according to claim 1 wherein the reading scan rate is a line scan rate and determining the line scan rate comprises: processing the movement of at least one eye from the eye tracker to detect line change eye movements by detecting eye movements in a direction opposite from a reading direction of a line or column in the electronic text; determining the user's line scan rate based on detected line change eye movements and a timer, the line scan rate being a numerical value indicative of a number of lines read per unit time; and calculating an estimate of the user's reading speed based on the line scan rate and supplementary scan rate data indicative of the average or actual quantity of electronic text per line. 3. The method according to claim 2 wherein the method comprises determining the user's line scan rate as an average line scan rate over multiple successive detected line change eye movements.