Grouping and emergent features in vision: Toward a theory of basic Gestalts.

Grouping and emergent features in vision: Toward a theory of basic Gestalts.

Pomerantz, James R.; Portillo, Mary C.

Journal of Experimental Psychology: Human Perception and Performance, Vol 37(5), Oct 2011, 1331-1349. doi: 10.1037/a0024330

Gestalt phenomena are often so powerful that mere demonstrations can confirm their existence, but Gestalts have proven hard to define and measure. Here we outline a theory of basic Gestalts (TBG) that defines Gestalts as emergent features (EFs). The logic relies on discovering wholes that are more discriminable than are the parts from which they are built. These wholes contain EFs that can act as basic features in human vision. As context is added to a visual stimulus, a hierarchy of EFs appears. Starting with a single dot and adding a second yields the first two potential EFs: the proximity (distance) and orientation (angle) between the two dots. A third dot introduces two more potential EFs: symmetry and linearity; a fourth dot produces surroundedness. This hierarchy may extend to collinearity, parallelism, closure, and more. We use the magnitude of Configural Superiority Effects to measure the salience of EFs on a common scale, potentially letting us compare the strengths of various grouping principles. TBG appears promising, with our initial experiments establishing and quantifying at least three basic EFs in human vision. (PsycINFO Database Record (c) 2011 APA, all rights reserved)

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Krista Overvliet, PhD.
 
Laboratory of  Experimental Psychology
University of Leuven
Tiensestraat 102, bus 3711
Room 00.74
3000 Leuven
Belgium
 
phone: +3216326146
skype: kristaovervliet
krista.overvliet@gmail.com
krista.overvliet@ppw.kuleuven.be
http://web.me.com/krista.overvliet

Context Modulates the ERP Signature of Contour Integration

 

 

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Context Modulates the ERP Signature of Contour Integration

via PLoS ONE Alerts: Neuroscience by Bart Machilsen et al. on 9/19/11

by Bart Machilsen, Nikolay Novitskiy, Kathleen Vancleef, Johan Wagemans

We investigated how the electrophysiological signature of contour integration is changed by the context in which a contour is embedded. Specifically, we manipulated the orientations of Gabor elements surrounding an embedded shape outline. The amplitudes of early visual components over posterior scalp regions were changed by the presence of a contour, and by the orientation of elements surrounding the contour. Differences in context type had an effect on the early P1 and N1 components, but not on the later P2 component. The presence of a contour had an effect on the N1 and P2 components, but not on the earlier P1 component. A modulatory effect of context on contour integration was observed on the N1 component. These results highlight the importance of the context in which contour integration takes place.

 

 

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AVA Xmas meeting 2011

Link: http://www.theava.net/conf/index.php?conference=Meeting&schedConf=X2011

"We will be celebrating sixteen years of AVA Christmas Meetings with a Meeting in York on Monday 19th December.



This is a one-day meeting to be held in the Department of Psychology at the University of York



This year's invited talks will include:

1) Matteo Carandini (Institute of Ophthalmology, UCL)

2) Karl Gegenfurtner CRS Guest lecture(Giessen University)

3) Hannah Smithson 2011 Marr Medal winner (University of Oxford)



Abstracts (max length: 250 words) should be submitted by November 1st on this website:



http:/www.theava.net/conf/



Abstracts will be peer-reviewed & published in the open-access journal i-Perception (so long as presenting authors attend the meeting) and should cover previously unreported research on any aspect of vision in humans, animals and machines."

Depth. Jan Koenderink, Andrea J van Doorn, Johan Wagemans

 

 

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Depth. Jan Koenderink, Andrea J van Doorn, Johan Wagemans

via i-Perception by Pion on 9/15/11

Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space, a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. The paper mainly deals with conceptual issues.

 

 

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