Invariance of the perceived spatial frequency shift of peripherally viewedgratings with manipulations of contrast, duration, and luminance

Gratings appear of higher spatial frequency when they are viewed peripheral ly rather than foveally. To test the hypothesis that this effect is an arte fact of particular laboratory conditions, we manipulated the contrast, lumi nance and presentation duration, manipulations which have also been shown t o increase the apparent spatial frequency of foveally presented gratings. I t has been argued that such shifts reflect an attempt to increase sensitivi ty by changing the receptive field properties of spatially tuned visual cha nnels, while keeping their size labels constant. If so, and peripheral chan nels are not otherwise mislabelled, it should be possible to find condition s under which the apparent spatial frequency of peripherally viewed grating s matches that of foveal gratings of the same spatial frequency. In this st udy, manipulations of contrast, luminance, and duration had no effect on th e size of the perceived spatial frequency shift in peripheral vision. Thus the putative inappropriate size labelling of peripheral visual channels is constant over a wide range of stimulus values. We speculate that this appar ent constant error may result from a mechanism which normally compensates f or another factor such as blur, which may otherwise lead to an overestimati on of size. (C) 2000 Elsevier Science Ltd. All rights reserved.