Localization of brief light stimuli on differently labelled reference patterns during smooth eye tracking.

Experiments are reported in which the mislocation of brief visual stimuli during tracking eye movements was measured in respect to three kinds of reference patterns placed in the horizontal plane--A) a scale with numbered divisions, B) a bar consisting of seven differently hatched regions; and C) two single markings, the distance between them being equal to the length of patterns A and B. A mislocation of a magnitude up to 2 degrees was obtained in all experiments. The mislocation on reference patterns A and C was the same, the presence of numbered markings did not influence it. The mislocation magnitude tended to decrease when reference pattern B was applied. Conclusion was made that clearly labelled structures near the place of stimulus presentation were a visual cue which affects localization; a scale with identical numbered markings, despite their proximity to the test stimulus, was not a structure of this type.