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Psychophysical Scaling: BBS Call for Commentators

Stevan Harnad harnad at PRINCETON.EDU
Mon Sep 16 23:30:47 EST 1991

Below is the abstract of a forthcoming target article to appear in
Behavioral and Brain Sciences (BBS), an international, interdisciplinary
journal that provides Open Peer Commentary on important and
controversial current research in the biobehavioral and cognitive
sciences. Commentators must be current BBS Associates or nominated by a
current BBS Associate. To be considered as a commentator on this
article, to suggest other appropriate commentators, or for information
about how to become a BBS Associate, please send email to:

harnad at clarity.princeton.edu  or harnad at pucc.bitnet        or write to:
BBS, 20 Nassau Street, #240, Princeton NJ 08542  [tel: 609-921-7771]

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. A
nonfinal draft of the full text is available for inspection by anonymous
ftp according to the instructions that follow after the abstract.


		Gregory R. Lockhead
		Department of Psychology
		Duke University
		Durham, NC 27706
		greg at psych.duke.edu (Lockhead)

KEYWORDS: assimilation, attribute, brightness, context, Fechner,
Gestalt, integral stimuli, judgment, loudness, objects, pitch,
psychophysical scale, sequence effects, Stevens

ABSTRACT: Psychophysical scaling models of the form R = f(I), where R
is the response and I is some intensity of an attribute, all assume
that people judge amounts of an attribute. With simple biases excepted,
most also assume that judgments are independent of space, time, and
other features of the situation apart from the one being judged. Many
data support these ideas: Magnitude estimations of brightness (R) do
increase with luminance (I). Nevertheless, I conclude that the general
model is wrong. One reason, suggested by the stabilized retinal image
literature, is that nothing is seen if light does not change over
time. A reason from the classification literature is that dimensions
often combine to produce emergent properties that cannot be described
by the elements in the stimulus. Further reasons are discussed. These
various effects cannot be adjusted for by simply expanding the general
model to the form R = f(X1, X2, X3, ... , Xn) because some factors do
not combine linearly. The proposed alternative is that people initially
judge the entire stimulus -- the object in terms of its environment.
This agrees with the constancy literature, which shows that objects and
their attributes are identified in terms of their relations to other
aspects of the scene. The fact that the environment determines
judgments is masked in scaling studies, where the standard procedure is
to hold context constant. In a typical brightness study where different
lights are presented on the same background on different trials the
essential stimulus for the observer might be the intensity of the light
or a difference between the light and the background. The two are
completely confounded. This issue is examined for audition. It is shown
that judgments of the loudness of a tone depend on the amount by which
that tone differs from the previous tone in both pitch and loudness. To
judge loudness (and other attributes) it is suggested that people first
process the stimulus object (the whole or integral thing) in terms of
differences between it and other aspects in the situation, and only
then do they assess the feature of interest. The conclusion is that
psychophysical judgments will be better interpreted by theories of
attention that are based on biology or psychology than by theories that
follow Fechner's lead and are based on classical physics.


To help you decide whether you would be an appropriate commentator for
this article, a (nonfinal) draft is retrievable by anonymous ftp from
princeton.edu according to the instructions below (the filename is
bbs.lockhead). 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 article.

        To retrieve a file by ftp from a Unix/Internet site,
	type either:
ftp princeton.edu
        When you are asked for your login, type:
        For your password, type your real name.
        then change directories with:
cd pub/harnad
        To show the available files, type:
        Next, retrieve the file you want with (for example):
get bbs.lockhead
        When you have the file(s) you want, type:

JANET users can make use of the online file transfer procedure
described by logging on to site UK.AC.NSF.SUN with password 'guestftp'
and userid 'guestftp', and making use of the help information available
on that machine.  Files transferred to a personal directory on the
NSF.SUN machine in this way may then be transferred to your own machine
using normal ftp.
        The above cannot be done form Bitnet directly, but there
        is a fileserver called bitftp at pucc.bitnet that will do
        it for you. Send it the one line message
        for instructions (which will be similar to the above,
        but will be in the form of a series of lines in an
        email message that bitftp will then execute for you).

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