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PubMed1978

Performance of MA-matched nonretarded and retarded children on discrimination learning and transfer-shift tasks.

The effects of the nature of the relevant dimension, response mode, imagery, and age on discrimination learning and shift performance was examined. Three age groups were used, CA 8 years-MA 8 years, CA 5 years-MA 5 years. CA 8 years-MA 5 years. The latter group learned both intradimensional and extradimensional shifts slower than did the former two groups. Subsequent analyses suggested that the reason for the slower learning in the retarded group was their greater frequency of control by dominant dimensions and/or the initial control by novel stimuli. A second finding was related to the particular procedure employed. Children were required to either press a button to indicate which of two stimuli was correct or pick up the correct stimulus. Form-relevant but not color-relevant problems were facilitated by the pick-up procedure. These findings suggest that dimensional dominance may be a consequence of the procedures employed in previous reports where children were or were not permitted to manipulate the stimuli.

Age Factors↗
PubMed1995

Lesions of the vertical lobe impair visual discrimination learning by observation in Octopus vulgaris.

We investigated whether lesions of the vertical lobe of the supraesophageal nervous mass of Octopus vulgaris impair discrimination learning acquired by observation of conspecific behavior. When tested alone, observer octopuses with about 50% of the vertical lobe removed showed a deficit in their learning by observation performance. The level of learning improved 24 h after the observational phase, when observer Octopus vulgaris showed a visual discriminatory performance significantly in agreement with the observed one. Control animals that had no brain tissue removed, did not show any impairment in the discriminative performance they had acquired vicariously. Removal of the vertical lobe of the octopus 'brain' has been reported to induce learning and memory deficits of visual discrimination in direct learning by conditioning experiments. Our findings support the conclusion that the removal of such brain center impairs short-term recall, but does not impair acquisition nor retention of 'observational' long-term memory.

Animals↗
PubMed1989

Sexual-discrimination learning in male Japanese quail (Coturnix coturnix japonica).

We investigated how male Japanese quail (Coturnix coturnix japonica) learn through extensive social and sexual experience to discriminate between male and female conspecifics. Opportunity for heterosexual copulation was important for this learning, but even extensive copulatory opportunity was not sufficient to produce a sexual discrimination; subjects also required exposure to other males. Exposure to females after copulatory opportunity did not produce a sexual discrimination but facilitated its acquisition. Time or exposure to only the visual features of male birds (provided by taxidermic models) after copulatory opportunity did not result in differential responding to male and female conspecifics. Finally, presenting stimulus birds one at a time proved to be a more sensitive test of sexual-discrimination learning than presenting two stimulus birds at the same time. The results indicate that sexual-discrimination learning is similar to conventional associative learning.

Animals↗
PubMedDate not supplied

Landmark discrimination learning in the dog.

Allocentric spatial memory was studied in dogs of varying ages and sources using a landmark discrimination task. The primary goal of this study was to develop a protocol to test landmark discrimination learning in the dog. Using a modified version of a landmark test developed for use in monkeys, we successfully trained dogs to make a spatial discrimination on the basis of the position of a visual landmark relative to two identical discriminanda. Task performance decreased, however, as the distance between the landmark and the "discriminandum" was increased. A subgroup of these dogs was also tested on a delayed nonmatching to position spatial memory task (DNMP), which relies on egocentric spatial cues. These findings suggest that dogs can acquire both allocentric and egocentric spatial tasks. These data provide a useful tool for evaluating the ability of canines to use allocentric cues in spatial learning.

Animals↗
PubMed2002

Sound improves visual discrimination learning in avian predators.

Aposematic insects use warning colours to deter predators, but many also produce odours or sounds when attacked by a predator. One possible role for these additional components is that they promote the association between the warning colour and the non-profitability it signals, thus reducing the chance of future attacks from visually hunting predators. This experiment explicitly tests this idea by looking at the effects of sound on a visual discrimination task. Young domestic chicks were trained to look for food rewards under coloured paper cones scattered in an experimental arena. In a subsequent visual discrimination task, they learned to discriminate between rewarded and non-rewarded hats on the basis of colour. Half the chicks performed this task in silence, whilst the other half had a tone played when they attacked non-rewarded hats. The presence of the tone improved the speed of colour discrimination learning. This demonstrates that there could be a selective advantage for aposematic coloured insects to emit sounds when attacked, since avian predators will learn to avoid their coloration more quickly. The role of psychological interactions between signal components in receivers is discussed in relation to the evolution of multimodal displays.

Acoustic Stimulation↗
PubMed1999

Rhinal cortex lesions produce mild deficits in visual discrimination learning for an auditory secondary reinforcer in rhesus monkeys.

Aspiration, but not neurotoxic, lesions of the amygdala impair performance on a visual discrimination learning task in which an auditory secondary reinforcer signals which of 2 stimuli will be reinforced with food. Because aspiration lesions of the amygdala interrupt projections of the rhinal cortex traveling close to the amygdala, it was hypothesized that damage to the rhinal cortex would severely impair learning in this task. Rhesus monkeys (Macaca mulatta) were trained to solve visual discrimination problems based on an auditory secondary reinforcer, were given lesions of the rhinal cortex or the perirhinal cortex alone, and were then retested. The monkeys displayed a reliable, albeit mild, deficit in postoperative performance. It is concluded that the aspiration lesions of the amygdala that produced a severe impairment did so because they interrupted connections of temporal cortical fields beyond the rhinal cortex that are also involved in learning in this task.

Acoustic Stimulation↗
PubMed1984

Chronic diazepam administration and appetitive discrimination learning: acquisition versus steady-state performance in pigeons.

Chronic injections of 2 mg/kg diazepam disrupted both steady-state performance and new discrimination learning in pigeons. However, the time course of disruption differed for each of the two tasks, i.e., steady-state performance was briefly disrupted early, whereas acquisition showed a more persistent delayed disruption. The difference was interpreted as resulting from a dual effect of diazepam on behavior. The early performance disruption was thought to reflect a general nonspecific sedative action of the drug, while the delayed disruption of learning was interpreted as the result of diazepam's selective interference with acquisition processes. Some support for rapid adjustment to the sedative effects of diazepam was found, but there was no evidence for the development of physiological tolerance to diazepam-induced acquisition deficits.

Animals↗
PubMed1991

Stimulus generalization, discrimination learning, and peak shift in horses.

Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms.

Animals↗
PubMed1990

Discrimination learning during the first year: stimulus and positional cues.

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues.

Attention↗
PubMed1990

A taste aversion model of drug discrimination learning: training drug and condition influence rate of learning, sensitivity and drug specificity.

A model of drug discrimination based on a lithium chloride (LiCl) flavour aversion was described and examined. Mildly thirsty rats were presented daily with 4 ml of a distinctly flavoured solution which was followed on 50% of the days by an IP injection of LiCl. Prior to the flavour presentation, the rats were injection SC with saline or a training drug (0.04 mg/kg fentanyl or 20 mg/kg pentobarbital) to signal whether LiCl would follow. Almost all rats eventually exhibited stable behaviour that involved drinking most or all of the fluid when it was not to be followed by LiCl and little or no drinking when it was. Such discrimination occurred regardless of whether drug predicted LiCl (learned-discomfort) or predicted no LiCl (learned-safety). However, with fentanyl there were clear differences between rats trained with drug under learned-safety and under learned-discomfort conditions for 1) the rate of acquisition of stable performance as a function of LiCl dose, 2) generalization of the training dose to a test dose that was lower, and 3) elicitation of fentanyl responses by pentobarbital. These findings, together with indications that such effects did not always occur with pentobarbital as the training drug, were discussed from theoretical and practical perspectives.

Animals↗
PubMed1992

Effects of bifemelane on discrimination learning of serotonergic-dysfunction rats.

To investigate the effect of bifemelane hydrochloride on learning achievements of serotonin-deficient rats, animals were fed with tryptophan-deficient diets and operant type discrimination learning tests were performed. In general, serotonin-deficient rats show hyperactivity. In this study, total number of responses in reverse learning experiments was lower in rats that received 50 mg/kg bifemelane compared to the other serotonin-deficient groups. The ratio of correct responses to the total number of responses revealed low learning achievements in the control and low-dose groups, whereas the ratio in the high-dose group was nearly the same as in normal rats in the final few sessions of both the primary and reverse learning experiments. Throughout this study, the high-dose group showed a better improvement in learning achievement than the low-dose group. Therefore, bifemelane has certain effects on learning achievement from a) the functional activation of the serotonergic nervous system and b) changes in neurotransmitter levels in the brain (e.g., acetylcholine, noradrenaline) and overall energy metabolism.

Animals↗
PubMed1999

Effects of excitotoxic lesions of the basolateral amygdala on conditional discrimination learning with primary and conditioned reinforcement.

Rats with excitotoxic lesions of the basolateral amygdala (BLA) were not impaired in the acquisition of an appetitive visuospatial conditional discrimination between stimuli varying in temporal frequency that has previously been shown to be sensitive to the effects of lesions of the striatum and cingulate cortex. After asymptotic performance was attained, discrimination was reinforced according to a fixed ratio (FR) schedule under which n presentations of sucrose were provided following n correct responses; each correct response also being reinforced immediately by a light acting as a conditioned reinforcer. Under these conditions of reinforcement when FRn=5, BLA-lesioned rats initially showed transient impairments in several aspects of performance, but rapidly attained control levels over subsequent test sessions. No further impairments occurred when FRn=10/20. However, in various conditions of extinction, further differences in performance were revealed between the BLA-lesioned and control groups, notably a significantly enhanced resistance to extinction when both sucrose and conditioned reinforcement were omitted. The results are discussed in terms of limbic-striatal mechanisms in the control of discrimination learning and the possible role of the amygdala in the mediation of different aspects of conditioned reinforcement.

Amygdala↗
PubMed1987

Tactile discrimination learning deficits in Alzheimer's and Parkinson's diseases.

Neuropsychological mechanisms of dementia in Alzheimer's and Parkinson's diseases were compared using a tactile discrimination learning paradigm adopted from animal models. There were two components to the task: tactile original learning (TOL), which is sensitive to parietal lobe damage in nonhuman primates; and tactile reversal of original learning (TRL), a measure of perseveration. The patients with Alzheimer's disease were significantly impaired on TOL compared with demented patients with Parkinson's disease, even though both groups were equated for severity of dementia. On TRL, the patients with Alzheimer's disease and demented patients with Parkinson's disease were both significantly impaired, but the patients with Alzheimer's disease showed significantly more perseverative errors. The mechanisms underlying TOL and TRL deficits may serve to differentiate Alzheimer's from Parkinson's dementia, and may involve selective parietal system lesions.

Aged↗
PubMed1975

Frequency of reinforcement as a determinant of extinction-induced aggression during errorless discrimination learning.

Seven pigeons were trained to discriminate without errors between a green keylight and a dark key. The key-pecking response was reinforced in the presence of green, and extinction was in effect in the presence of the dark key. The opportunity to attack a restrained target pigeon was present only during extinction. Both variable-interval 30-sec and fixed-ratio 1 schedules of reinforcement during the positive stimulus induced a higher rate of attack during extinction than a variable-interval 5-min schedule. The highest rate of attack during extinction occurred during the first 20 sec after the positive stimulus terminated. Hence, the withdrawal of the positive condition, rather than the consequences of the pecking response during extinction, appears to be one of the primary factors responsible for attack between pigeons during extinction. Behavioral contrast, defined as a decrease in the rate of responding when the positive stimulus was presented alone, was obtained from the four birds that displayed the lowest overall rates of attack while the three birds with the highest attack rates did not display behavioral contrast. For the birds without contrast, components of the attack response during the positive stimulus presumably competed with and reduced the rate of pecking the key, thereby recluding behavioral contrast.

Aggression↗
PubMed1983

Concept discrimination learning by preschool children using facial stimuli differing in age, sex, race, and eyeglasses.

In two experiments, the relative salience of the variables age, sex, race, and eyeglasses was determined with the use of a discrimination learning task and preschool-age Ss. The stimuli for the task were 112 frontal head and shoulder color photographs arranged in pairs. In both experiments, sex discrimination was the easiest to learn, followed by race and age, which did not differ from each other. Each of the variables of sex, age, and race, however, proved to be more salient than glasses which was not learned by any of the 19 Ss who were given a glasses discrimination problem in Experiment 1. Interestingly, specific cue salience may be a more valid concept than dimensional salience for preschool children. This was indicated by the asymmetry in performance on the black and white racial discrimination problems and on the male and female sexual discrimination problems: both black and male were significantly easier to learn.

Age Factors↗
PubMed1988

Conditional discrimination learning in Aplysia californica.

Two experiments examined whether the relation between a conditioned stimulus (CS) and an unconditioned stimulus (US) might be brought under the control of contextual stimuli in the invertebrate Aplysia californica. Subjects received exposure to 2 different contexts. In both experiments, a tactile CS was paired with a shock US in one of those contexts. In the other context, that tactile CS was either nonreinforced (Experiment 1) or explicitly unpaired with the shock US (Experiment 2). Responding to the CS during a subsequent test was greater in the context in which that CS had been paired with the US compared with the context in which it had been nonreinforced or unpaired. These findings are discussed in terms of theories of conditional discrimination learning.

Animals↗
PubMed1975

Form preferences in successive discrimination learning of young chicks.

In four experiments the effects of form and orientation pecking preferences of 1- and 3-day old Vantress X Arbor Acre chicks on successive discrimination learning were determined, using heat reinforcement. Major findings were as follows: (a) The young chick has both circle and verticle orientation pecking preferences that are present during at least the first 3 days after hatching; (b) when either of these preferred cues is the nonreinforced cue, the young chick has difficulty in learning not to respond to it but learns quickly not to respond to an unpreferred cue (e.g., triangle and horizontal oriented dots or bar); and (c) these pecking preferences can be modified by heat reinforcement, and the effects of this conditioning is evidenct in subsequent extinction and retention tests. The main conclusion from these experiments is that form and orientation preferences, like brightness and color preferences, are important developmental constraints on conditioning of the young chick.

Age Factors↗