Peripheral vision and perceived visual direction

Experiments are described in which the subjects had to localize brief light stimuli presented up to 10 degrees from the fixation center. The localization was performed relative to a continuously illuminated scale with numbered or lettered divisions. Systematic errors were obtained, the stimuli being mislocated nearer the fixation point than they were actually presented. The angular size of errors increased with the increase of stimulus eccentricity. It appeared to be a characteristic of the stimulated retinal locus, independent of the viewing distance and the scale element corresponding to this locus. It is concluded that despite the presence of a visible background frame of reference, subjects prefer to base their reports on the perceived egocentric direction of the stimulus which does not coincide with the physical direction of the stimulus. A parallel is drawn between this study and the studies on serial position function for letter identification.