The construction of peripheral appearance

Lecture
Date: 
14 May 2019
Begin time: 
16:15
End time: 
17:45
Room: 
CITEC 2.015

Our visual system is extremely anisotropic across the visual field. By the time the peripheral visual input reaches visual cortex, its representation has lower resolution, larger positional uncertainty, and a generally warped geometry according to cortical magnification.
Yet, we have the impression the world in front of us does not change as we move our eyes, in fact, to a large extent we have the impression that our visual field is uniform. How does this illusion come about?

I will present results concerning three fundamental mechanisms that inform the way our peripheral visual appears.
The first mechanism is foveal to peripheral extrapolation, specifically in the domain of brightness perception. Here we show that the brightness of the foveally viewed portion of an object biases the perceived brightness of the regions of the same surface that are viewed peripherally.
The second mechanism is trans-saccadic re-calibration. With this we refer to the finding that peripherally perceived size can change if observers are exposed to a consistent alteration of the mapping between peripheral, pre-saccadic size and foveal, post-saccadic size.
The third mechanism is the reliance on priors. Our results show that when observers match the appearance of peripherally viewed artificial and natural images, they tend to report them to be sharper and more regular than they actually are.

We claim that all those mechanisms contribute to construct the appearance of a peripheral visual field which is qualitatively more similar to the foveal one, thus reducing the perceived anisotropy of the visual field and trans-saccadically experienced discrepancy.