Vection is enhanced by visual oscillation based on four-stroke apparent motion

Illusions of self-motion (vection) can be improved by adding global visual oscillation to patterns of optic flow. Here we examined whether adding apparent visual oscillation (based on four-stroke apparent motion—4SAM) also improves vection. This apparent vertical oscillation was added to self-motion displays simulating constant velocity leftward self-motion. Our psychophysical experiment found that adding 4SAM oscillation to this optic flow significantly shortened the onset latency, and increased the rated strength, of our participants’ vection. Interestingly, we found that the vection onset latencies in this 4SAM oscillation condition were similar to those produced when “real” oscillation was instead added to the optic flow—even though adding “real” oscillation (based on the global and continuous displacement of dots over time) generally resulted in stronger vection experiences. These results show vection can be enhanced by both “real” and apparent 4SAM visual stimuli indicating self-acceleration. They also confirm that global visual displacements are not required to generate these oscillation-based advantages for vection.