IDENTIFICATION ASYMMETRY OF PARAFOVEAL STIMULUS PAIRS

Three experiments, involving 8, 10, and 10 naive participants, respectively, were conducted to examine the phenomenon in which the peripheral member of a parafoveally appearing stimulus pair is more accurately identified than the central. In the first experiment, the asymmetry was observed with stimulus pairs which had but one distinguishing feature; this could have implications for the notion that feature perturbations between stimuli provide the basis for the effect. The second experiment eliminated an explanation based upon acuity at the position of the midpoint of the stimulus configuration, since the asymmetry remains when this position is held constant. The involvement of response or decision factors seems unlikely, since the third experiment found the effect with blocked presentations involving responses to only one member of the pair. It is concluded that accounts which appeal to difficulties in separating stimuli from the overall pair configuration fail to explain more accurate identification of the peripheral stimulus when the pair is positioned at a constant distance from fixation. © 1979 Psychonomic Society, Inc.