The visual saltation illusion expanding and contracting: Determining the impact of flash duration and ISI

Abstract

This study renders the visual saltation illusion (VSI) into an expansion and a contraction transformation mode, diverging from traditional experiments using translation. Small-, medium-, and large-sized stimuli were used to create conditions akin to VSI translation experiments. Participants fixated on a cross while three stimuli (expanding or contracting) flashed 25.9° below. Despite actual size, observers consistently misperceived the second flash as medium-sized relative to the first and third flash. Further experiments were conducted to determine whether stimulus duration or interstimulus interval had more of an effect inducing the VSI. These results showed that for expansion and contraction, the VSI did not favor either parameter, but overall favored short stimulus onset asynchronies below 317 ms. These findings shed more light on the VSI phenomenon and open the doors on presenting the VSI in other modes.