Intermodal transfer from a visual to an auditory discrimination using an errorless learning procedure

Errorless learning is a technique developed by Terrace [Terrace, H.S., 1963a. Discrimination training with and without “errors”. J. Exp. Anal. Behav. 6, 1-27] to train stimulus discriminations with few or no errors. In the first replication of the original findings, errorless learning was also shown to transfer successfully between two visual discriminations without errors [Terrace, H.S., 1963b. Errorless transfer of a discrimination across two continua. J. Exp. Anal. Behav. 6, 223-232]. In the present experiment, we extended the errorless learning procedure to an intermodal transfer, from a discrimination between red and green colors to a discrimination between high and low tones. The pigeons were divided into two groups: an Experimental Group, which learned both discriminations through errorless learning, and a Control Group, which learned them through trial-and-error. Results showed that pigeons from the Experimental Group learned the red-green discrimination with significantly fewer errors than the Control Group and that errorless learning is effective in transferring from a visual to an auditory discrimination.     

Learning set formation in slow lorises (Nycticebus coucang)

In primates, learning set formation has been reported in various simian species, but in only few prosimian species. The formation of visual discrimination learning set was tested on a nocturnal prosimian species, slow lorises (Nycticebus coucang). Their performance was higher than that of some New World monkeys. This confirmed the suggestion from the data on black lemurs (Lemur macaco) that there is an overlap between prosimians and simians in learning set ability.     

Discriminations, reversals, and extra-dimensional shifts in the Göttingen minipig

G?ttingen minipigs were trained on a set-shifting procedure involving discriminations, reversals, and extra-dimensional shifts. The discriminations used were black-white discriminations and right-left discriminations. The initial visual and spatial discrimination seemed equally difficult, and only for the visual modality was reversal found to be more difficult than the initial discrimination. Visual reversal was more difficult than spatial reversal, and a larger number of perseverative sessions were found for visual reversal compared to spatial reversal. The acquisition of the extra-dimensional shift from the visual to the spatial dimension was not inferior to the learning of spatial reversal. Neither was the acquisition of the extra-dimensional shift from the spatial to the visual dimension inferior to the learning of visual reversal. Thus, no evidence was found for attention to stimulus dimensions in discrimination learning of the pigs.     

Prosimian sensory capacities

This paper reviews laboratory research on sensory capacities of prosimians. Most investigations to date have concentrated on visual and auditory sensitivity with relatively little attention directed toward olfactory and gustatory sensitivity. Diurnal prosimians have at least rudimentary color vision and appear deficient to anthropoids in other visual measures such as acuity. The most striking difference between prosimian and anthropoid auditory sensitivity is the increased sensitivity of the former group to high frequencies. No psychophysical data have been published on olfactory sensitivity of prosimians, but the relatively large olfactory areas in their brains and their propensity for scent marking strongly suggest that they have acute olfactory sensitivity. Most data on gustatory thresholds in prosimians does not permit sensitivity estimation since the data are joint functions of sensitivity as well as preferences.     

Comparison of visual and olfactory reversal learning in pigeons

Pigeons trained to discriminate between either two differentodors or two different colored lights acquired their discriminationsat the same rate. When the discrimination problems were reversedwithin a modality, however, the birds using visual cues acquirednew discriminations more rapidly than in original learning (positivetransfer), whereas the birds using olfactory cues acquired thediscrimination reversal less rapidly. On subsequent reversals,pigeons in the visual task condition developed a successivediscrimination reversal set with repeated reversals of the stimuli,while those in the olfactory condition did not. In a secondexperiment designed to assess the acquisition of redundant cues,birds received additional training with visual and olfactorycues in compound as discriminative stimuli, and were then testedwith only visual or olfactory cues. Birds previously trainedwith odor attended to visual cues in the compound, whereas birdspreviously trained to discriminate between lights did not attendto odor cues until they were presented alone. These resultsdemonstrate that the selection of stimuli may play a crucialrole in the performance of successive discrimination reversalsand suggest that, in contrast to rats, birds selectively attendto visual over olfactory cues in discrimination learning.     

The fossil evidence of anthropoid brain evolution

The endocast of Aegyptopithecus, a 27 million year old ape, reveals that its brain was advanced over that of prosimians and comparable to that of modern anthropoids in relative size and in having expanded visual cortex, reduced olfactory bulbs, and a central sulcus separating primary somatic sensory and motor cortex. The early appearance of those features suggests that they may have been among the adaptations responsible for the evolution of anthropoids from prosimian ancestors. The frontal lobe was relatively smaller in Aegyptopithecus than in modern anthropoids. An endocast of Dolichocebus, one of the oldest known New World monkeys (25–30 million years old), reveals visual cortex expanded as in modern anthropoids. The 19 million year old Napak frontal bone displays a hominoid rather than cercopithecoid sulcal pattern. An 18 million year old endocast of the ape Dryopithecus (Proconsul) was neither monkey-like nor primitive, as originally described, but rather apelike and essentially modern in all observable features. The oldest undoubted Old World monkey endocast, from nine million year old Mesopithecus, reveals that the brain was modern in sulcal pattern and proportions. The sulcal pattern was like that of modern colobines, but that appears to be the more primitive condition, from which features characteristic of modern cercopithecine brains have evolved. The brain of six million year old Libypithecus was similar to that of Mesopithecus. A two million year old endocast of “Dolichopithecus” arvernensis displays a modern cercopithecine sulcal pattern.     

Chimpanzees (Pan troglodytes): Problem seeking versus the bird-in-hand,least-effort strategy

Fifteen adult chimpanzees were tested on a series of tasks that differed from standard two-choice object discrimination learning problems in one detail: a third choice was sometimes offered, and it consisted of clearly visible and readily accessible food. Even under conditions where they would have to score 100% on the discrimination learning tasks to get as much food as they could get by taking the “free” food, many of the chimpanzees worked on the problems. Individual differences were large and reliable. Frequency of response to a given problem also varied according to how accurately the animals were performing and increased markedly if the hidden food was made a few grams larger than the free food. The chimpanzees did not rely strictly on a “bird-in-hand” strategy or necessarily always work to get the maximum amount of food with the minimum amount of energy expenditure. Whether this is bad economics or good economics depends on the time scale on which one views adaptation.     

A multivariate approach reveals the behavioral templates underlying visual discrimination in rats

Although rodents are the first-choice animal model in the life sciences, they are rarely used to study higher visual functions. It is unclear to what extent rodents follow complex visual strategies to solve visual object recognition and discrimination tasks [1-5]. We report the performance of rats in a visual discrimination task applying the multivariate "Bubbles" paradigm previously used in highly visual species such as humans, monkeys, and pigeons [6-8]. We demonstrate a relationship between accuracy and local occlusion of stimuli by bubbles, as such revealing the strategies or "templates" that underlie visual discrimination behavior. Performance was guided by relatively simple, screen-centered templates as well as more adaptive templates reflecting context dependency and tolerance for changes in stimulus position. These findings demonstrate the complexity of visual strategies followed by rats and reveal interesting similarities (e.g., potential for position tolerance) as well as differences (overall efficiency of visual processing) compared to primates. In conclusion, this study illustrates the feasibility of investigating visual cognition in rats with multivariate behavioral paradigms, with the ultimate aim to use a comparative approach to explore the anatomical and neurophysiological basis of vision, also for those visual abilities that are traditionally studied in humans and monkeys.     

Spatial memory during foraging in prosimian primates: Propithecus edwardsi and Eulemur fulvus rufus

A variety of anthropoids travel efficiently from one food source to another, although there is disagreement over how this is accomplished over large-scale space. Mental maps, for example, require that animals internally represent space, geometrically locate landmarks, use true distance and direction, and generate novel shortcuts to resources. Alternately, topological or route-based maps are based on a network of fixed points, landmarks and routes so that one food patch can be linked with another. In this study we describe travel patterns between food sources for two prosimian species found in southeastern Madagascar, Propithecus edwardsi and Eulemur fulvus rufus. Both species are dependent on fruit and have large home range sizes. By comparing interpatch distances, patch size and turning angles, we found that both species prefer nearest neighbor food patches and P. edwardsi travels in relatively straight lines. The amount of backtracking seen in E. f. rufus may be linked to their large group size and dependence on large-crowned fruit trees. We suggest that the goal-oriented foraging of both prosimian species is dependent on a topological or route-based map. These are rare behavioral data relevant to ecological and social contexts of primate cognitive evolution.     

Visual Discrimination Learning in the Small Octopus Octopus ocellatus

Octopus ocellatus is a small benthic species of octopus that is easy to rear and spawns large eggs during a short life cycle. These and other features of O. ocellatus may make it an advantageous subject for a broad range of behavioral studies, including those involving various types of learning. However, no type of learning has been studied in O. ocellatus. In a successive visual discrimination task, in which a ‘positive’ or ‘negative’ stimulus (white or black rectangle) was presented to a subject octopus and appropriate rewards or punishments were given to the subject, the rate of ‘correct’ responses (i.e., touches to the positive stimulus or refraining from the negative stimulus) gradually increased. Moreover, ‘observer’ octopuses that observed another octopus performing a visual discrimination task in which reward was also given to the ‘incorrect’ responses (touches to the negative stimulus) showed a higher ratio of incorrect responses in their test sessions. These results, coupled with the physical characteristics of O. ocellatus, indicate that this species is potentially suitable for neurogenetic and neuroembryological studies of learning.     

Performance of African elephants (Loxodonta africana) and California sea lions (Zalophus californianus) on a two-choice object discrimination task

This study documents the ability of African elephants (Loxodonta africana) and California sea lions (Zalophus californianus) to perform a two-choice object discrimination task. Both species were able to perform this task. However, California sea lions took fewer trials overall to reach a criterion of 10 consecutively correct responses than did African elephants. The performance of California sea lions did not change significantly during this study. However, African elephants showed a gradual learning of the task, as exhibited by a gradual decrease in the number of trials needed to reach criterion. This performance difference may reflect differences in either visual abilities or cognitive functioning, which in turn may be influenced by either different evolutionary pressures exerted on herbivores and carnivores, or by the context in which visual information is used in the lives of these animals. © 1994 Wiley-Liss, Inc.     

Evidence for time-place learning in the Morris water maze without food restriction but with increased response cost

Time-place learning is the ability to distinguish between resources that vary in location at different times of day. Only one previous report has demonstrated successful time-place learning without using food as reward. In this experiment, satiated rats failed to form time-place discriminations in a Morris water maze while food deprived rats did, leading to the conclusion that food system activation is necessary for time-place learning. However, in addition to food system activation, response cost was also increased, which previously has been demonstrated to be effective in allowing the formation of time-place discriminations. The purpose of these two experiments is to test whether food system activation or heightened response cost allowed for time-place learning in the Morris water maze. In the first experiment, we replicate the failure to find time-place discriminations in the Morris water maze without food restriction and without increased response cost. In the second experiment, we found that increased response cost without food restriction was effective in allowing the formation of a time-place discrimination. The implications of this result are discussed in light of the timing mechanism used for time-place discriminations, the nature of the response cost, and the event-time-place tripartite association.     

Transfer index and mediational learning in tufted capuchins (Cebus apella)

The transfer index (TI) is a discrimination reversal paradigm that requires the achievement of a given prereversal criterion of accuracy. The mediational learning (ML) paradigm is a modification of the TI procedure that features the presentation of three different reversal conditions designed to assess whether prereversal learning is based on purely associative processes or mediated by the use of a strategy (win-stay/lose-shift). These two paradigms have been used with apes and several Old World monkey species, proving to be effective tools for the comparison of species on the basis of their transfer abilities and the nature of their learning processes. However, among New World monkeys, only the squirrel monkey has been tested. Capuchin (Cebusspp.) adaptability and their mastery in using tools have led to controversial interpretations of their cognitive and learning skills. We evaluated their mode of learning and the transfer of learning using the TI and the ML paradigms. We tested four tufted capuchins (Cebus apella)in a WGTA using a variety of stimulus object pairs. The results show that they possess rather good transfer abilities and one subject showed an associative learning mode. None of the subjects showed evidence of learning mediated by a win-stay/lose-shift strategy.     

The performance of ravens on simple discrimination tasks: a preliminary study

Recent studies suggest the existence of primate-like cognitive abilities in corvids. Although the learning abilities of corvids in comparison to other species have been investigated before, little is known on how corvids perform on simple discrimination tasks if tested in experimental settings comparable to those that have been used for studying complex cognitive abilities. In this study, we tested a captive group of 12 ravens (Corvus corax) on four discrimination problems and their reversals. In contrast to other studies investigating learning abilities, our ravens were not food deprived and participation in experiments was voluntary. This preliminary study showed that all ravens successfully solved feature and position discriminations and several of the ravens could solve new tasks in a few trials, making very few mistakes.     

Recognition of incomplete patterns by bumble bees

Bumble bees were trained to discriminate between two visual patterns, one of which was rewarding (S+) and one of which was unrewarding (S-). Subsequently, they were tested for discrimination between two non-rewarding patterns: the top halves of the training patterns, the bottom halves or the side halves. Three conditions were tested: (1) When the S+ was a star and the S- was a circle, all halves of the star were chosen above chance level, which may reflect an unlearned preference for radial patterns. (2) When the S+ and S- were reversed, the bottom half and the side half of the circle were chosen above chance level, but not the top half. (3) In the last condition, the S+ was again a circle, but the feeder tube was placed below the training pattern rather than above, and again the bottom halves were discriminated but neither the top nor the side halves were. In learning pattern discriminations, the ventral portion of the pattern is weighted more strongly than the dorsal portion, which enables recognition of incomplete patterns, and the weighting depends little on angle of approach.     

Separate attentional resources for vision and audition

Current models of attention, typically claim that vision and audition are limited by a common attentional resource which means that visual performance should be adversely affected by a concurrent auditory task and vice versa. Here, we test this implication by measuring auditory (pitch) and visual (contrast) thresholds in conjunction with cross-modal secondary tasks and find that no such interference occurs. Visual contrast discrimination thresholds were unaffected by a concurrent chord or pitch discrimination, and pitch-discrimination thresholds were virtually unaffected by a concurrent visual search or contrast discrimination task. However, if the dual tasks were presented within the same modality, thresholds were raised by a factor of between two (for visual discrimination) and four (for auditory discrimination). These results suggest that at least for low-level tasks such as discriminations of pitch and contrast, each sensory modality is under separate attentional control, rather than being limited by a supramodal attentional resource. This has implications for current theories of attention as well as for the use of multi-sensory media for efficient informational transmission.     

VISUAL ACUITY AND ILLUMINATION IN DIFFERENT SPECTRAL REGIONS

The relation between visual acuity and illumination was measured in red and blue light, using a broken circle or C and a grating as test objects. The red light data fall on single continuous curves representing pure cone vision. The blue light data fall on two distinct curves with a transition at about 0.03 photons. Values below this intensity represent pure rod vision. Those immediately above represent the cooperative activity of rods and cones, and yield higher visual acuities than either. Pure cone vision in this intensity region is given by central fixation (C test object). All the rest of the values above this transition region represent pure cone vision. In blue light the rod data with the C lie about 1.5 log units lower on the intensity axis (cone scale) than they do in white light, while with the grating they lie about 1.0 log unit lower than in white light. Both the pure rod and cone data with the C test object are precisely described by one form of the stationary state equation. With the grating test object and a non-limiting pupil, the pure rod and cone data are described by another form of the same equation in which the curve is half as steep. The introduction of a small pupil, which limits maximum visual acuity, makes the relation between visual acuity and illumination appear steeper. Determinations of maximum visual acuities under a variety of conditions show that for the grating the pupil has to be larger, the longer the wavelength of the light, in order for the pupil not to be the limiting factor. Similar measurements with the C show that when intensity discrimination at the retina is experimentally made the limiting factor in resolution, visual acuity is improved by conditions designed to increase image contrast. However, intensity discrimination cannot be the limiting factor for the ordinary test object resolution because the conditions designed to improve image contrast do not improve maximum visual acuity, while those which reduce image contrast do not produce proportional reductions of visual acuity.     

Infanticide in Propithecus diadema edwardsi: An Evaluation of the Sexual Selection Hypothesis

Infanticide might be described as a reproductive strategy employed by anthropoid primate males when they immigrate into new groups. But infanticide has rarely been observed in wild prosimian primates. For the Malagasy lemurs this may reflect one or more of the following: strict breeding seasons; relative monomorphism in canine tooth and body size; small group sizes; male–female dominance relations; and male–female dyads within groups. We addressed the following questions: Do prosimian males commit infanticide in circumstances similar to those in which anthropoids do? and Is there any reproductive advantage for a highly seasonal breeder to commit infanticide? To help answer these questions, we describe the death of a 24-hr-old infant male Propithecus diadema edwardsi from wounds received during a fight between his mother, her adult daughter, and a newly immigrant male. Interbirth intervals between surviving offspring are 2 years for Propithecus diadema edwardsi; therefore, a male could dramatically shorten the time between reproductive windows by killing an infant. Whether this tactic would be favored by sexual selection cannot be addressed until more information has been collected on the length of interbirth interval due to infanticide relative to that of infant death by other causes; how social factors such as stability of breeding relationships affect long-term male reproductive success; how effective female counterstrategies are to prevent infanticide and/or whether they choose to mate with males that commit infanticide; and how often males that kill infants subsequently sire infants, particularly in groups that contain a resident male.     

Simultaneous processing of spatial and chromatic components of patterned stimuli by the human visual system

We report measurements on discrimination of orientation and magnification made for elements differentiated in colour and/or luminance from their background. By performing measurements at a series of background luminances and for fixed luminance of the elements, we show that with colour contrast, discrimination for both spatial parameters is unimpaired when the background is at isoluminance with the elements. Under simple luminance contrast, however, these discriminations become poorer when the background luminance is within some +/- 5% of that of the elements, and are completely absent when the two values are the same. A deuteranomalous subject is unable to make the spatial discrimination around the isoluminance point for colour contrasts which are too small for him to distinguish, but for which subjects with normal colour vision maintain spatial discriminations at isoluminance. This observation establishes that the physiological mechanisms of normal colour vision, rather than stimulus artefacts, mediate the observed spatial discriminations. We conclude that the visual processing of colour and spatial parameters such as orientation and magnification are intrinsically related to each other.     

The Ferrier lecture, 1989. Outlooks for blindsight: explicit methodologies for implicit processes

In primates the retina is connected with different targets in the brain via several parallel pathways, the largest of which is that going to the lateral geniculate nucleus of the thalamus and thence to the striate cortex, the geniculo-striate pathway. When this route is damaged in man, apparent blindness in a corresponding part of the visual field occurs, despite the integrity of the other parallel pathways. In animals, it has been demonstrated by conventional behavioural forced-choice techniques that extrastriate routes can sustain a variety of visual discriminations. Comparable discriminations are also possible in some human subjects with geniculo-striate damage when forced-choice 'guessing' techniques are used. 'Blind-sight' refers to those subjects who state that they are unaware of the visual stimuli, even when performing discriminations at high levels of proficiency. Extensions of this approach are reviewed, especially to spectral sensitivity and movement discrimination. But residual capacities can also be assessed without requiring guessing responses, thereby avoiding issues of differential response criteria and other practical difficulties. Effects of 'unseen' stimuli in the cortically blind field on the visible perception of concurrent stimuli in the intact field can be measured. Also, positive reactions of the autonomic nervous system, such as the galvanic skin response, can be recorded to visual stimuli presented in the blind field. Recent evidence demonstrates that the pupil in normal adult subjects is systematically sensitive to structural and chromatic features of visual stimuli. Pupillometry reveals specific changes and residual capacities in visual-field defects of adult patients with striate cortical damage. Thus non-verbal and sensitive methods are available that permit the comparative study of normal and residual visual capacity in human infants, adults and infra-human animals.