Response times to different spatial frequencies:

Stanley, Howell, and Smith (1980) present an alternative analysis of the persistence data obtained by Bowling and Lovegrove (1980). They argue that stimulus onset asynchrony (SOA) is a more appropriate measure of persistence than interstimulus interval (ISI). In addition, they propose that the use of this measure alters the conclusion made by Bowling and Lovegrove (1980) that the stimulus duration at which persistence ceases to decline steeply with increasing stimulus duration increases with spatial frequency and is related to temporal integration. We consider that SOA is a measure of the total duration of the response to a stimulus, rather than of persistence, and use of this measure does not affect the major conclusions of Bowling and Lovegrove (1980). Stanley et al. (1980) also mentioned that a nonlinear continuous function may provide a better fit to Bowling and Lovegrove’s data than a two-limb linear function. This possibility was evaluated by fitting linear, quadratic, and logarithmic functions to the data by the method of least squares. The sums of the squared deviations of the data points from each of these regression relationships and from the two-limb linear relationship were calculated. Table 1 shows that, for each spatial frequency, the deviation of the data points from the two-component linear relationship was lower than that for any other relationship. The two-limb relationship is therefore a better fit to the data than any of the other possibilities investigated.