1985 - Sociedade Brasileira de Psicologia

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squares and his task was to assign nx=hers to repteseat how far auay the
markers looked to hfm. The method of free-modulus magnfeude estimatfon was
used and to the observer was read instructfons whfch eaphasized tbe use of
whatever nu'abers seemëd appropriate to represent apparent dlstances.
fnctudtng those lass e'1' (fractfons or deefmats). Each observer served for
five sessions scheduted oa 4 dtfferent fntersessfon intervat.. Th. followtng
delays after Sessfon 1 were used: 1 day. l week. 1 month. and 9 month. Delay
was awithln-subjects vartable.
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The Psychophysical Function - For each observer. a straight ttne was
fitted by the xethod of leas t squaresp relating 1og magnitude estfmates to
1og actual dfstancel. Its slope.which fs the exponent of a power function.
the scale factor. and the coefficient of determlnatfon.m2.were deterained
for each observer in each sesston.The mean exponents. consfderfng a11
sessions . varfed from 1.08 to 1.24. These values shog good agreement wfth
those obtafned and analyzed by 3aird (1). Teghtsoonian and Teghtsoonfant7).
Da Sflva (3). and Wiest and Bell (1t)pwho found a aean expodent greater
than 1.0 for the power function reldtfng percefved dfstance to phyaical
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dfstance for indoor settfngs. An analysts of varfance showed no effect of '
session on exponent,altboujh t*e effect of subjectswas sfgnificant.The
good quallty of the ffts for individuat observera is fndieated by the mean
coefficients of deterainatfon. for fndfvfdual fftted tines. These
coefficients varied from .96,ço ogg'betveen sessions vhen the values were
pooled across observers.
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tntercorretatfons of observers' Exponents.w T*e Pearson oorrelations
coaeuted between sessions varfed from .70 to.97. Each correlatlon vas
sfgnfficantly hfgh: fndicatfng that the observer'a exponent ls cloaely
related to bls perfov-nnce on the prevfous session.These correlatfons.
together thesfgnifâcanteffect of sublects on exponentspiùdfcate
perpfscing indtvidual differences tn exponentsy that âs. despfte a 9 months
tntervats betueen sesslons.observers showed consfstency ta Magaltude
estimates for apparent distance.
Within-trial Reliabftfty - Wfthfn-erfal reliabîlftkes of fndivfdual
exponents were exnwn'ned by calcutating exponents both for the first trfal
of judgmentsof each targetdfstanc d then for the second trial.The
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