SIZE SCALING AND ITS EFFECT ON LETTER DETECTION

Two ways of scaling letter size across eccentricity were investigated in a choice reaction time (CRT) task. Experiments 1 and 2 tested corti cal magnification theory (M-scaling), while Experiment 3 used scaled s izes drawn from Anstis's regression formula (A-scaling). Experiment 4 compared both scaling techniques, together with the effect of exposure duration and the absolute size of the foveal letter. Results showed t hat scaling effectiveness improved when large rather than small foveal letters were used. A-scaling with a large foveal letter provided a go od fit for the data at parafoveal locations, but underestimated the le tter sizes needed at large eccentricities. M-scaling with a large fove al letter size produced CRTs that were independent of eccentricity. Ex posure duration did not substantially affect performance.