shift invariance

[Edelman Shimon]

> Date: Tue, 5 Mar 96 17:33:00 +0100
> From: Eric Postma <postma at cs.rulimburg.nl>
> 
> DeLiang Wang wrote
> >I'd like to know the evidence that the visual system achieves shift
> >(translation) invariance (I'd appreciate references if any). 
> 
> Biederman and Cooper (1991) found that an object presented at one location
> of the retina facilitated recognition of that object at other locations. The
> visual system does not achieve perfect ranslation invariance as shown by
> Nazir and O'Regan (1991).
> 
> Biederman, I. & Cooper, E.E.  (1991).                                    
> Evidence for complete translational and reflectional invariance in visual
> object priming.
> Perception, 20, 585-593.
> 
> Nazir, T.A. & O'Regan, J.K. (1990).
> Some results on translation invariance in the human visual system.
> Spatial Vision, 5, 81-100.

Putting Nazir & O'Regan on the same list with Biederman like that may
be misleading to someone who will not bother to read the paper. Nazir
& O'Regan actually found evidence AGAINST translation invariance in
human vision. They may have phrased the title conservatively to
appease conservative reviewers... So, do not take the existence of
translation invariance in biological vision for granted; heed well the
cautionary note in Norberto's posting:

> Date: Mon, 4 Mar 1996 11:03:09 -0800 (PST)
> From: Norberto Grzywacz <nmg at skivs.ski.org>

> A form of shift invariance appears to exist in cortical neurons of the 
> anterior part of the superior temporal sulcus and of the inferior temporal 
> cortex.  Neurons in these areas have large receptive fields, which can show 
> considerable selectivity for what the stimulus is irrespective of exactly 
> where it is in the visual field.  I would call this property "selectivity 
> shift invariance," to contrast with "absolute shift invariance," which 
> the cortex does not appear to have. 

-Shimon

Dr. Shimon Edelman, Applied Math. & Computer Science
Weizmann Institute of Science, Rehovot 76100, Israel
The Web:  http://eris.wisdom.weizmann.ac.il/~edelman
fax: (+972) 8 344122   tel: 8 342856   sec: 8 343545