[From Rupert Young 970710 1200 BST]

This forwarded message may be of interest to CSGers. The phrase
"representation of similarities" seems reminiscent of reference and
perceptual signals.



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Date: Wed, 9 Jul 1997 19:03:45 +0100
Reply-To: BBS - Behavioral and Brain Sciences <>
From: BBS - Behavioral and Brain Sciences <bbs@COGLIT.SOTON.AC.UK>
Subject: Representation of Similarities: BBS Call for Commentators
To: Multiple recipients of list COLORCAT <COLORCAT@BROWNVM.BROWN.EDU>

    Below is the abstract of a forthcoming BBS target article on:


        by Shimon Edelman

This article has been accepted for publication in Behavioral and Brain
Sciences (BBS), an international, interdisciplinary journal providing
Open Peer Commentary on important and controversial current research in
the biobehavioral and cognitive sciences.

Commentators must be BBS Associates or nominated by a BBS Associate. To
be considered as a commentator for this article, to suggest other
appropriate commentators, or for information about how to become a BBS
Associate, please send EMAIL to:

      or write to:

    Behavioral and Brain Sciences
    Department of Psychology
    University of Southampton
    Highfield, Southampton

If you are not a BBS Associate, please send your CV and the name of a
BBS Associate (there are currently over 10,000 worldwide) who is
familiar with your work. All past BBS authors, referees and commentators
are eligible to become BBS Associates.

To help us put together a balanced list of commentators, please give
some indication of the aspects of the topic on which you would bring
your areas of expertise to bear if you were selected as a commentator.
An electronic draft of the full text is available for inspection
with a WWW browser, anonymous ftp or gopher according to the
instructions that follow after the abstract.


                                Shimon Edelman
                                Center for Biological and Computational
                                Dept. of Brain and Cognitive Sciences
                                MIT E25-201
                                Cambridge MA 02142 USA

        KEYWORDS: representation, similarity, visual shape recognition,
    categorization, perception, features, invariance, mental models,
        affordance, constancy, distal/proximal stimulus, isomorphism

    ABSTRACT: Advanced perceptual systems are faced with the problem of
    securing a principled (ideally, veridical) relationship between the
    world and its internal representation. I propose a unified approach to
    visual representation, addressing the need for superordinate and
    basic-level categorization and for the identification of specific
    instances of familiar categories. According to the proposed theory, a
    shape is represented internally by the responses of a small number of
    tuned modules, each broadly selective for some reference shape, whose
    similarity to the stimulus it measures. This amounts to embedding the
    stimulus in a low-dimensional proximal shape space spanned by the
    outputs of the active modules. This shape space supports
    representations of distal shape similarities that are veridical as
    Shepard's (1968) second-order isomorphisms (i.e., correspondence
    between distal and proximal similarities among shapes, rather than
    between distal shapes and their proximal representations).
    Representation in terms of similarities to reference shapes supports
    processing (e.g., discrimination) of shapes that are radically
    different from the reference ones, without the need for the
    computationally problematic decomposition into parts required by other
    theories. Furthermore, a general expression for similarity between two
    stimuli, based on comparisons to reference shapes, can be used to
    derive models of perceived similarity ranging from continuous,
    symmetric, and hierarchical, as in multidimensional scaling [Shepard,
    1980], to discrete and non-hierarchical, as in the general contrast
    models [Tversky, 1977; Shepard and Arabie, 1979].

- --------------------------------------------------------------
To help you decide whether you would be an appropriate commentator for
this article, an electronic draft is retrievable from the World Wide
Web or by anonymous ftp or gopher from the US or UK BBS Archive.
Ftp instructions follow below. Please do not prepare a commentary on
this draft. Just let us know, after having inspected it, what relevant
expertise you feel you would bring to bear on what aspect of the

The URLs you can use to get to the BBS Archive:

To retrieve a file by ftp from an Internet site, type either:
   When you are asked for your login, type:
   Enter password as queried (your password is your actual userid:
   yourlogin@yourhost.whatever.whatever - be sure to include the "@")
cd /pub/harnad/BBS
   To show the available files, type:
   Next, retrieve the file you want with (for example):
get bbs.edelman
   When you have the file(s) you want, type:

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