Visual discrimination

This study was a partial replication of one previously
reported by Nash and Michels (1966). The purpose was to investigate
perceptual form discrimination behavior of young
squirrel monkeys as affected by contextual variables of the
stimulus. The variables examined were Redundancy, Position
and, of the form itself, Complexity. In addition, a sequential
method of testing and recording was compared with
the conventional 50-trial block procedure. Two 17 month old monkeys were tested on eight twochoice
problems in a Purdue General Test Apparatus. The
problems each consisted of two slides on which pairs of
random shapes were presented. The shapes within each pair
of slides were held constant on the parameters investigated.
One slide was designated as the positive stimulus and presented
in either the right or left position in random order. The number of correct responses for the 50-trial
blocks, as examined by an analysis of variance, failed to
reach statistical significance for any of the variables
investigated. However, graphic inspection of the data
suggests general agreement with the findings of Nash and
Michels (1966). In comparing the two methods of testing,
the sequential test of performance (STOP) was equally as
effective as the conventional method and could have provided
a substantial savings in test time. Comparison of
scores obtained by the two procedures shows good correlation. Although no strong conclusions can be drawn from the
data, they do lead to the speculation that there is a relationship
between effect and extent of redundancy, and
that failure of S to make a correct response in the test
situation may be the result of cue sampling rather than a
failure to discriminate.

The viewing behavior of three adult male squirrel
monkeys (Saimiri soiureus) to several visual incentives
was studied by a paired-comparison testing technique. The total number of times and total duration of time
that Ss viewed each incentive, at each window of a two-window
cubicle, were recorrlerl automatically. The total
duration of time Ss spent in visual exploration was relatively
stable over days, averaging 40 per cent of the
total testing time. Ss spent more time (p< .01) viewing
another monkey than a toy snake or an empty plexiglass
cage. Differences in time spent viewing the
latter two incentives were not significant. Habituation
to visual incentives (i.e., decrement in mean drration
per response) was demonstrated over successive
half-hour intervals within days (p < .01), but not over
successive days. Differences in rate of habituation between
visual incentives were not significant. Differences
in rate of extinction following acquisition on
each visual incentive were not significant.

Prior research has explored the counterchange model of motion detection in terms of counterchanging information that originates in the stimulus foreground (or objects). These experiments explore counterchange apparent motion with regard to a new apparent motion stimulus where the necessary counterchanging information required for apparent motion is provided by altering the luminance of the background. It was found that apparent motion produced by background-counterchange requires longer frame durations and lower levels of average stimulus contrast compared to foreground-counterchange. Furthermore, inter-object distance does not influence apparent motion produced by background-counterchange to the degree it influences apparent motion produced by foreground-counterchange.

The electrosensory and visual adaptations of elasmobranchs to the environment have been more studied than most other senses, however, work on these senses is mostly limited to descriptive analyses of sensitivity, morphology, and behavior. The goal of this work was to explore electrosensory and visual capabilities in a more ecological context. To gain an understanding of the content of bioelectric signals, the magnitude and frequency of these stimuli were recorded from a broad survey of elasmobranch prey items... Color vision adaptations also correlated to the photic environment of each species; cownose rays inhabit turbid, green-dominated waters and had two cone visual pigments that maximize contrast of objects against the green background... Yellow stingrays were trichromatic and likely possess the ability to discriminate colors in their clear, reef and seagrass habitats, which are spectrally rich. Both species showed evidence of ultraviolet sensitivity, which may aid in predator and conspecific detection as an enhanced communication channel. Future studies should investigate the integration of sensory input and sensory involvement in intraspecific communication to gain more insight into ecological adaptations.

Little is known about the visual capabilities of marine turtles. The ability to discriminate between colors has not been adequately demonstrated on the basis of behavioral criteria. I used a three-part methodology to determine if color discrimination occurred. FIrst, I exposed naèive, light-adapted hatchlings to either a blue, green or yellow light. I manipulated light intensity to obtain a behavioral phototaxis threshold to each color, which provided a range of intensities we knew turtles could detect. Second, I used food to train older turtles to swim toward one light color, and then to discriminate between the rewarded light and another light color ; lights were presented at intensities equally above the phototaxis threshold. Lastly, I varied light intensity so that brightness could not be used as a discrimination cue. Six turtles completed this task and showed a clear ability to select a rewarded over a non-rewarded color, regardless of stimulus intensity. Turtles most rapidly learned to associate shorter wavelengths (blue) with food. My results clearly show loggerheads have color vision. Further investigation is required to determine how marine turtles exploit this capability.

The central importance of vision to an organism is evident in the anatomical and physiological adaptations within the eye that can be correlated to the organism's behavior and ecology. The goal of this study was to perform a functional analysis of adaptations within the elasmobranch visual system. An integrative approach was used to examine morphological and physiological adaptations in several species and link these adaptations to phylogeny, locomotion, habitat, behavior and ecology. Functional aspects investigated were eye position, pupil shape, spectral sensitivity, temporal resolution, the extent of the visual field and ultimately the integration of the visual and electrosensory systems. The elasmobranch eye adapts to the light environment of its habitat. Sharks from similar habitats had similar spectral sensitivities such as the bonnethead and blacknose sharks, both maximally sensitive to blue light of 480 nm. The spectral sensitivity of the scalloped hammerhead, which lives in a different environment, was maximally sensitive to green light (530 nm). The temporal characteristics of the eye also matched habitat and lifestyle. Species experiencing variable light conditions exhibited increased critical flicker-fusion frequencies, such as the bonnethead (31 Hz) and scalloped hammerhead (27 Hz), in contrast to deeper or more nocturnal species such as the blacknose shark (18 Hz). Elasmobranch visual fields correlated to each species' lifestyle, habitat and foraging strategy. Expansive monocular views, including a 360° panoramic view in the yellow stingray, were measured in species that rely on vision for vigilance against predators.

When interpreting how an animal "learns" discrimination tasks, strain capabilities must be considered, and it should be shown that they comprehend the task in a manner consistent with the given interpretation. A novel visual-discrimination (VD) task for relative-size-relations was used to examine visual cue use in C57BL/6J mice, which are shown to have biologically good vision and neurologically intact memory for VD tasks. Results suggest C57BL/6J strain may not be fully capable of relative cue-size associations or even object recognition-based on a water maze VD task. This is in contrast to previous studies suggesting this mice strain is quite strong in visual skills and on VD tasks. Additionally, cue size and/or cue-pairings do appear to influence specific directional preferences or stereotyped behaviors as trainings continued, and these strategies shifted during novel probes. Future studies should assess how mice discriminate between objects and test rat's capabilities on this task.