j *@ - Sociedade Brasileira de Psicologia

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constancy irl the violet smctral re#on was fotmd to be perfectly independent of the
illumination cbnnges. '
For the sake of direct comparison, colour constancy in man was tested using
the exact same arrangement, but with the appropriate set of i lminating lights (i.e.
blue, green, and red light). The test procedure was the same as that described for the
honeybee, and only yes or no Rnqwers were accepted. Colour constancy was again
tested in different spectral regions. Good colour constancy was observed in the bluishpeen
regon, where the =me colour match was carried out as in the honeybee. For a
colour match in the red-green region, a lack of colour constancy was observed.
This indicates a different performance in colour constancy which correlates
with different sm ctral regons and ilxmination changes. It is interesting to note, that a
similar systematic deficiency in colour corlstancy withf resped to chzomatic regions is
also found in the honey bee. n ls, the term colour constancy does not seem to be
appropriate in describing the performance of the visual system in coding colours under
different illumination conditions.
1H. Proc- es underlying colom constancy
Colour perception is not only determined by the spectrai content of the light
stim ulating the receptors, and thus the trichromatic 4heory of colour vision does not
reflect all the processes involved in colour coding. So, which neural mechanisms are
responsible for colour constancy? The most simple explanation would be a selective
chromatic adaptation of the photoreceptors or adaptation of more central stations of
inform ation processing, such as the spectralepponent system . The other hypothesis
would be to prerxme spatial interactions whièh would provide for a chromstic-spatial
intepation - as mentioned in the introduction for man.
To test tltis hypothesis, colour-constancy was tested in two different
ççMondrian''-arrangem ents for the snme pair of training' and matching plates in the
violet region of the spedrum . The two arrangements bnly differ with respect to the
extent of area available for spatial œtegration. Adaptational influences do not differ
for the two situations. . . .
(a) 3-l1e1d Moridrian: In tlzis Mondrian, 3 violet phtes are available for integrational
processes. A colour constancy test, as described above , ks carried out with
mntching between 2 plates. Adaptational processes ilz neurons which are stimulated by
the training-and mntching-plate are identical to that occm ring in the 13-fie1d Mondrian .
Result : The alternative plate is mistaken for the training-plate . ln other
words, there is a lack of colour constancy.
(b) 7-field Mondrian: The nme training and matcling colour were tkqed as
described above in a). There are 5 additional plates in the display, but they are
separated from the training apd matching plate by 5 cm . The bee is trained not to fly