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DAVID INGLE
constancies, susceptibility to illusions, or the ability to view different
pairs of stimuli as having the same mutual relationships. Very often these
studies stimulate the scientific imagination, only to leave the reader
hungry for solid proof of the inherent claims. Nevertheless, the scholarly
reader will be interested in the array of observations and experiments
reviewed by Herter ( 1953).
The first aim of the analytical approach is a physical description of
the essential attributes of visual objects which guide their “recognition”
or their “discriminability.” Objects can be distinguished along various
dimensions-size, brightness, color, distance, orientation, and motionand psychologists have usually assumed that each dimension has a discrete physiological basis. Neurophysiologists have discovered within the
visual pathways of various vertebrate species single neurons that are, in
fact, tuned in to specific dimensions of the stimulus: brightness, color,
orientation, or motion. Some of the data of perception is filtered out
within the retina and along the retinofugal pathways, and other data are
provided by internal central processes ( or other sensory modalities) whose
function can be tenuously and imprecisely inferred. The present studies
offer relevent information in approaching the first question of selectivity
of the visual system: What features of the visual array do fish particularly
notice?
One kind of analysis likely to reflect limits of peripheral visual
processing is the measurement of minimum separable acuity. Weiler
(1966) obtained threshold acuity values of 5.3 min of visual angle,
averaging the performance of three “Oscars,” Astronotus ocellatus, required to discriminate finely spaced dot patterns from a solid gray plaque.
Taking the calculations of Brunner (1935), this limiting angle approximates the diameter of single retinal cones. Of course acuity of primates
and some avian species measures far less than their cone diameters. Perhaps the fish has not evolved a mechanism for extracting this additional
information through “temporal integration” of signals from the moving
retinal image.
A second area of research where retinal physiology ought to prove
useful to the psychologist is that of color vision. The analysis of goldfish
cones by Marks (1965) reveals three separate retinal photopigments and
seems to imply that this species should possess trichromatic color vision.
A logical proof that fish had color vision at all awaited the study
of McCleary and Bernstein (1959) who showed that generalization between pairs of colored stimuli (red and green) could not be attributed
to brightness cues, after first determining their subjects’ judgement as to
the relative brightness of the critical stimuli. More recently, Muntz and
Cronly-Dillon (1966) obtained evidence that goldfish color vision was
very probably trichromatic: their subjects could distinguish reds, greens,
DAVID INGLE
constancies, susceptibility to illusions, or the ability to view different
pairs of stimuli as having the same mutual relationships. Very often these
studies stimulate the scientific imagination, only to leave the reader
hungry for solid proof of the inherent claims. Nevertheless, the scholarly
reader will be interested in the array of observations and experiments
reviewed by Herter ( 1953).
The first aim of the analytical approach is a physical description of
the essential attributes of visual objects which guide their “recognition”
or their “discriminability.” Objects can be distinguished along various
dimensions-size, brightness, color, distance, orientation, and motionand psychologists have usually assumed that each dimension has a discrete physiological basis. Neurophysiologists have discovered within the
visual pathways of various vertebrate species single neurons that are, in
fact, tuned in to specific dimensions of the stimulus: brightness, color,
orientation, or motion. Some of the data of perception is filtered out
within the retina and along the retinofugal pathways, and other data are
provided by internal central processes ( or other sensory modalities) whose
function can be tenuously and imprecisely inferred. The present studies
offer relevent information in approaching the first question of selectivity
of the visual system: What features of the visual array do fish particularly
notice?
One kind of analysis likely to reflect limits of peripheral visual
processing is the measurement of minimum separable acuity. Weiler
(1966) obtained threshold acuity values of 5.3 min of visual angle,
averaging the performance of three “Oscars,” Astronotus ocellatus, required to discriminate finely spaced dot patterns from a solid gray plaque.
Taking the calculations of Brunner (1935), this limiting angle approximates the diameter of single retinal cones. Of course acuity of primates
and some avian species measures far less than their cone diameters. Perhaps the fish has not evolved a mechanism for extracting this additional
information through “temporal integration” of signals from the moving
retinal image.
A second area of research where retinal physiology ought to prove
useful to the psychologist is that of color vision. The analysis of goldfish
cones by Marks (1965) reveals three separate retinal photopigments and
seems to imply that this species should possess trichromatic color vision.
A logical proof that fish had color vision at all awaited the study
of McCleary and Bernstein (1959) who showed that generalization between pairs of colored stimuli (red and green) could not be attributed
to brightness cues, after first determining their subjects’ judgement as to
the relative brightness of the critical stimuli. More recently, Muntz and
Cronly-Dillon (1966) obtained evidence that goldfish color vision was
very probably trichromatic: their subjects could distinguish reds, greens,