3. THE EXPERIMENTAL ANALYSIS OF VISUAL BEHAVIOR
73
prepared to see. Observations of fish locomotion and associated eye
movement also suggest selective visual operations during behavior. It
is even possible that “internalized” selection occurs when the fish rests in
place, so that only selected features of the visual array (or selected
portions of the visual array) have full access to central processes. If this
were so, it would impose still another barrier between the psychologist
and the neurophysiologist who is usually restricted to an anesthetized
or paralyzed preparation. While there is little conclusive evidence at the
behavioral side for selective attention, the issue is so important that a
review of the few relevant facts may be of heuristic value.
Some fish move one eye at a time in response to a moving object,
while the other eye stares indifferently into space. One suspects, without
direct evidence, that the redirected eye must be the more sensitive at
that moment, in connection with the motor dominance of one hemisphere.
Visual behavior toward objects appearing within the binocular field of
a moving fish presents the same issue. Harris (1965) has shown for the
dogfish that eye movements are asymmetrical during the sideward waggling of the head: The eye toward which the head swings is momentarily
stabilized by compensatory reflexes in reference to a locus of points 3
feet to the side of the fish. Trevarthen (1968a) showed that compensatory eye movements in a spinalized goldfish are likewise asymmetrical.
It seems that a locomoting fish must either accept double vision within
the binocular field or attend selectively to information arriving the
stabilized eye.
We do know that fish can use both eyes simultaneously during a
discrimination task when stimuli appear within the lateral fields. Ingle
( 1968a) trained goldfish to compare stimuli seen via opposite eyes (i.e.,
to avoid an unlike pair such as horizontal plus vertical stripes) while
treating a horizontal or a vertical pair as “no go” stimuli. Another experiment in this series showed that goldfish do not ignore monocular information even where it is irrelevant and where it would be to their advantage. Subjects learning a vertical-horizontal stripe discrimination via one
eye also viewed the horizontal stimulus via the opposite eye on each trial.
On critical “attention” trials, the “no go” horizontal pair was changed by
inserting a novel red-on-white horizontal striped stimulus on one side
or the other. Subjects were disinhibited by the red color more often via
the irrelevant eye which contradicts the hypothesis that they would
suppress visual processes on the nondiscriminating side.
Attention might be shifted to particular dimensions of analysis (size,
orientation, brightness, etc.) as well as to selected regions of the visual
field, as Mackintosh (1965a) has suggested on the basis of experiments
with rats. Hemmings (1966) has tested one prediction of this model,
using tropical fish: that a difficult discrimination will be more efficiently
73
prepared to see. Observations of fish locomotion and associated eye
movement also suggest selective visual operations during behavior. It
is even possible that “internalized” selection occurs when the fish rests in
place, so that only selected features of the visual array (or selected
portions of the visual array) have full access to central processes. If this
were so, it would impose still another barrier between the psychologist
and the neurophysiologist who is usually restricted to an anesthetized
or paralyzed preparation. While there is little conclusive evidence at the
behavioral side for selective attention, the issue is so important that a
review of the few relevant facts may be of heuristic value.
Some fish move one eye at a time in response to a moving object,
while the other eye stares indifferently into space. One suspects, without
direct evidence, that the redirected eye must be the more sensitive at
that moment, in connection with the motor dominance of one hemisphere.
Visual behavior toward objects appearing within the binocular field of
a moving fish presents the same issue. Harris (1965) has shown for the
dogfish that eye movements are asymmetrical during the sideward waggling of the head: The eye toward which the head swings is momentarily
stabilized by compensatory reflexes in reference to a locus of points 3
feet to the side of the fish. Trevarthen (1968a) showed that compensatory eye movements in a spinalized goldfish are likewise asymmetrical.
It seems that a locomoting fish must either accept double vision within
the binocular field or attend selectively to information arriving the
stabilized eye.
We do know that fish can use both eyes simultaneously during a
discrimination task when stimuli appear within the lateral fields. Ingle
( 1968a) trained goldfish to compare stimuli seen via opposite eyes (i.e.,
to avoid an unlike pair such as horizontal plus vertical stripes) while
treating a horizontal or a vertical pair as “no go” stimuli. Another experiment in this series showed that goldfish do not ignore monocular information even where it is irrelevant and where it would be to their advantage. Subjects learning a vertical-horizontal stripe discrimination via one
eye also viewed the horizontal stimulus via the opposite eye on each trial.
On critical “attention” trials, the “no go” horizontal pair was changed by
inserting a novel red-on-white horizontal striped stimulus on one side
or the other. Subjects were disinhibited by the red color more often via
the irrelevant eye which contradicts the hypothesis that they would
suppress visual processes on the nondiscriminating side.
Attention might be shifted to particular dimensions of analysis (size,
orientation, brightness, etc.) as well as to selected regions of the visual
field, as Mackintosh (1965a) has suggested on the basis of experiments
with rats. Hemmings (1966) has tested one prediction of this model,
using tropical fish: that a difficult discrimination will be more efficiently