We examined the relationship between cognitive states and visually-induced self-motion perception, i.e. “vection” (latency, duration and magnitude). It is often anecdotally reported that time experienced in return travel (back to the start point) seems shorter than time spent in outward travel (travel to a new destination). Here, we report the first experimental results showing that return travel time is experienced as shorter than the actual time because of perceiving vection. Secondary, we explore how numbers are represented in depth in our mental space, we asked participants to sequentially speak random numbers while they observed forward/backward vection. We found that participants tended to generate larger numbers when they perceived backward self-motion. Finally, We found that all the measures of vection correlated negatively with the degree of narcissistic traits of participants.