Fig. 6

One of the authors demonstrates how the measurements were conducted (here experiment 2): A 32 cm high support made sure the distance to the stimuli was the same for all participants. The subject fixated the tip of a ballpoint pen starting at the target sign and then moved the pen left away from the target until the target could no longer be seen in the corner of the eye. That point was then marked on the paper and the distance entered as the conspicuity index