| Hemispheric asymmetry in processing spatial frequency information has been investigated using various paradigms which have yielded conflicting outcomes. No study to date, however, has held constant the stimulus parameters assumed to affect spatial frequency, while directly manipulating the spatial frequencies in the stimuli themselves. In the present study, photos of faces with neutral affect were tachistoscopically presented to 15 males and 15 females with no known neurological or ophthalmologic disease. The faces were masked either with square wave gratings of 1, 24, or 48 cycles/degree, or presented alone without a mask for a stimulus duration of 10 msec. Both mask and target stimuli were presented simultaneously, and luminance was held constant across all conditions. Accuracy in recognizing the target face from a group of five served as the dependent measure.;These main effects were modified strongly by a significant hemifield by frequency interaction (p < .0001). As was hypothesized, LVF errors were highest with the low spatial frequency mask (1c/d), while RVF errors were highest with the use of the higher spatial frequency grating (24 c/d). Sex was not a significant main effect nor did it interact significantly with any of the other factors.;These results confirm that the left and right hemispheres show a differential efficiency in processing higher and lower spatial frequency information in faces, respectively. They also offer empirical evidence to support the clinical findings that both hemispheres contribute to facial recognition. Implications of these results for the re-interpretation of previous findings, as well as how these relate to current theories of hemispheric specialization are discussed.;ANOVA results included significant main effects of frequency (P < .0001) and hemifield (p < .002). Overall, left visual field (LVF) presentations yielded the most errors. Post hoc comparisons revealed that the error rates for the various masking conditions did not differ significantly from each other, but significant differences were noted between the unmasked condition and each of the individual masking conditions. |
