Eye movements during perceptual switches in the pointing triangles illusion

Attneave´s (1968) pointing triangle illusion consists of a display of ipsilateral triangles. Perceiving the display results in the illusion that the triangles point in a certain direction. Spontaneous switches in pointing direction are observed. Blink frequency significantly decreases before the switches witnessing for a nonspecific preparation process to perceptual and motor response events. Saccade angles in the pointing triangles illusion reveal a relation to the switches. It was found that during inspection of the triangles the saccade angles are random only in a condition where subjects try to refrain from switching. Usually during inspection subjects have two dominant gaze directions corresponding to the axes of possible switches about 500 ms before the switch. The results provide evidence for a crucial role of eye movements in this illusion and against the influence of the manual response.