On the relativity of perceived motion

Area of Science:

• Neuroscience
• Vision Science
• Perceptual Psychology

Background:

• Visual stability during eye movements is traditionally attributed to extraretinal signals matching retinal signals.
• Discrepancies between these signals are thought to initiate motion perception.

Purpose of the Study:

• To investigate the traditional explanation of visual stability during smooth pursuit eye movements.
• To determine the precise conditions under which motion is perceived during ocular pursuits.

Main Methods:

• Motion perception thresholds were measured during smooth pursuit eye movements.
• The magnitude of the just noticeable difference (JND) was analyzed in relation to ocular velocity and stimulus motion direction.

Main Results:

• The traditional view is incomplete; motion perception requires a difference exceeding a just noticeable difference (JND).
• The JND magnitude is dependent on ocular velocity but independent of stimulus motion direction.
• Retinal image motion does not independently convey information about stimulus motion.

Conclusions:

• Ocular velocity is accurately represented in extraretinal signals, challenging previous theories.
• Perceived motion, direction, and velocity are relative, depending on the JND and extraretinal signals.
• This framework explains phenomena like the Filehne illusion and Aubert-Fleischl phenomenon, with potential applications to vestibular effects.