Abstract
Primates use eye movements to bring and keep objects of interest in the fovea, the region of highest visual acuity, presumably to facilitate object recognition. Therefore, we measured in two experiments how eye movements affect the performance for recognizing letters. The letters were presented within a noise patch, which was either stationary (fixation) or moved horizontally with 10.57 deg/sec (pursuit). It was defined by a one octave wide, band pass filtered noise, with a central frequency of 3 cycles per letter. In the first experiment we compared letter recognition performance during steady state pursuit and fixation over a range of presentation durations and contrast levels. In the second experiment, subjects had to make a vertical 7.5 deg saccade to the stimulus before either fixating or pursuing it. In this case, the letters were presented at different points in time after saccade onset. The results show that letter recognition is only slightly impaired during steady-state pursuit. To reach the same level of performance, either more presentation time or more contrast is required. The same was true for fixation and pursuit after an initial saccade. However, in the later case the recognition rate increased slowly with time relative to saccade onset and reached a plateau only at around 150 ms. In sum these results show that object recognition of moving objects is quite good during pursuit. After saccades, object recognition takes longer to reach a stable level of performance than expected from saccadic suppression, which lasts 50 to 100 ms. Acknowledgement: This work was supported by the DFG Forschergruppe FOR 560 “Perception and action” and the DFG Graduiertenkolleg GRK 885 “NeuroAct”.
DFG Forschergruppe FOR 560 “Perception and Action” and the DFG Graduiertenkolleg GRK 885 “NeuroAct”.