A motion-induced position shift that depends on motion both before and after the test probe

Saki Takao, Akira Sarodo, Stuart Anstis, Katsumi Watanabe, Patrick Cavanagh

Research output: Contribution to journalArticlepeer-review

Abstract

Two versions of the flash grab illusion were used to examine the relative contributions of motion before and motion after the test flash to the illusory position shift. The stimulus in the first two experiments was a square pattern that expanded and contracted with an outline square flashed each time the motion reversed producing a dramatic difference in perceived size between the two reversals. Experiment 1 showed a strong illusion when motion was present before and after the flashed tests or just after the flashes, but no significant effect when only the pre-flash motion was present. In Experiment 2, motion always followed the flash, and the duration of the pre-flash motion was varied. The results showed a significant increase in illusion strength with the duration of pre-flash motion and the effect of the pre-flash motion was almost 50% that of the post-flash motion. Finally, Experiment 3 tested the position shifts when the linear motion of a disk before the flash was orthogonal to its motion after the flash. Here, the results again showed that the pre-flash motion made a significant contribution, about 32% that of the post-flash motion. Several models are considered and even though all fail to some degree, they do offer insights into the nature of the illusion. Finally, we show that the empirical measure of the relative contribution of motion before and after the flash can be used to distinguish the mechanisms underlying different illusions.

Original languageEnglish
Pages (from-to)19
Number of pages1
JournalJournal of Vision
Volume22
Issue number12
DOIs
Publication statusPublished - 2022 Nov 1

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

Fingerprint

Dive into the research topics of 'A motion-induced position shift that depends on motion both before and after the test probe'. Together they form a unique fingerprint.

Cite this