Abstract
In a recent publication, Westheimer concluded that the foveal line-separation discrimination function was smooth [ J. Opt. Soc. Am. A 1, 683– 684 ( 1984)]. However, when the Westheimer data are replotted in the Weber-fraction (Δs/s) form, segments in the discrimination function similar to those previously described by Hirsch and Hylton [ J. Opt. Soc. AM. 72, 1367– 1374 ( 1984)] can be observed.