he experiment was designed referencing to Wiliams and Borow (1963), Drury and Forsman’s (1996) study [12,14]. The target was a Landolt broken ring with a gap at left or right. There were four groups with two between- subject factors (i.e. velocity and time pressure). For the low velocity groups the velocity was 4 / s while 14 / s was selected as high velocity. The time corresponding to 63.2% of the cumulative detection probability was the time limit of the low time pressure groups and 50% as the high time pressure groups (See Yu and Chan [15]). It had been proved in author’s other research that participants applied random search strategy for both velocities. According to the random search model (For detailed explanation of the model, see Chan and Chan (2000) [16]), the two velocities correspond to the following two models according to the author’s previous research (These two models were derived under no time pressure, see Yu and Chan [15]):