Visual recognition in the peripheral field: letters versus symbols and adults versus children.

The plot of the form-resolving field (FRF) was obtained by tachistoscopically presenting two figures in each stimulus, one in the center of gaze and the other in the peripheral field. The figures in the periphery were placed at various eccentricities in different presentations. The ensuing plot of average letter recognition as a function of eccentricity is the FRF. Only the horizontal components of the FRFs were used in the comparisons. Three sets of figures were used as stimuli: regular-size letters, large-size letters, and symbols. Three groups of subjects were compared: adult ordinary readers, reading children, and pre-reading-age children. The last were tested with symbols only. In letter recognition, the FRFs for young and adult ordinary readers are similar and fall off monotonically and symmetrically with eccentricity, hence conforming with the first Aubert-Foerster law (1857). However, the FRFs tested with symbols are narrower than those tested with letters of the same sizes and stroke widths, which is not in accordance with the first Aubert-Foerster law. In addition, the FRFs of symbols are different for each subject group. It is suggested that recognition in the peripheral field is not determined by visual acuity alone; rather, it is further confined or determined by the visual strategy employed to accomplish the task, and its associated distribution of lateral masking.