Does an estimate of environmental size precede size scaling on a form-comparison task?

In a number of studies reaction time has been found to increase with increases in size ratio on a same -different form-comparison task. Bennett and Warren (2002, Perception & Psychophysics 64 462-477) teased apart environmental and retinal size ratios by showing the forms along a (simulated) texture hallway, viewed monocularly, on a simultaneous form-comparison task; roughly equal effects of environmental and retinal size ratios were found. The current study enhanced scene-size information by showing the forms in simulated stereo and by adding texture to the forms themselves; special care was also taken to perceptually isolate the stimuli. In two experiments, with different kinds of forms, strong effects of environmental size ratio were found; no effect of retinal size ratio (same trials) was observed in either experiment. The results support the hypothesis that the (same-trial) form-size codings reflect 'all told' estimates of environmental size, and place constraints on modeling the functional architecture of the visual system.