Simple Simultaneous Discrimination Research Articles

PERFORMANCE OF OLDER ADULTS AND COLLEGE STUDENTS IN A TASK OF REVERSAL LEARNING

This study aimed to compare the learning and reversal of simple visual discriminations in two groups of healthy participants, matched in relation to education, however, differing in age. Twelve college students (aged 18 to 24 years) and 13 healthy older adults (aged 60 to 77 years), all with at least 12 years of education, learned three simple simultaneous visual discriminations, followed by three successive stimulus function reversal tests. All the participants learned the discriminations; however, only seven older adults achieved the criterion in the reversal tests. All the young participants achieved the criterion in the reversals. Among the older adults that did not achieve the criterion, a non-perseverative error pattern was the most common, with performance declining during the exposure to the reversal tests.

The Midsession Reversal Task with Pigeons Does a Brief Delay Between Choice and Reinforcement Facilitate Reversal Learning?

In a midsession reversal task, the session begins with a simple simultaneous discrimination in which one stimulus (S1) is correct and the other stimulus (S2) is incorrect (S1+/S2-). At the midpoint of the session, the discrimination reverses and S2 becomes the correct choice (S2+/S1-). When choosing optimally, a pigeon should choose S1 until the first trial in which its choice is not reinforced and then it should shift to S2 (win-stay/lose-shift). With this task, pigeons have been shown to respond suboptimally by anticipating the reversal (making anticipatory errors) and continuing to choose S1 after the reversal (making perseverative errors). This suboptimal behavior may result from a pigeon’s relative impulsivity due to the immediacy of reinforcement following choice. In other choice tasks, there is evidence that the introduction of a short delay between choice and reinforcement may decrease pigeons’ impulsivity. In the present experiment, a delay was introduced between stimulus selection and reinforcement to assess whether it results in a decrease in anticipatory and perseverative errors. Pigeons that had a delay between choice and reinforcement were a bit slower in acquiring the midsession reversal task compared to those without a delay, but showed no decrease in either anticipatory or perseverative errors. It is likely that the pigeons’ natural tendency to use time from the start of the session to the reversal as a cue to reverse prevented the delay from increasing accuracy on this task.

The midsession reversal task: A theoretical analysis.

In the midsession reversal task, choice of one stimulus (S1) is correct for the first half of each session and choice of the other stimulus (S2) is correct for the last half of each session. Although humans and rats develop very close to what has been called a win-stay/lose-shift response strategy, pigeons do not. Pigeons start choosing S2 before the reversal, making anticipatory errors, and they keep choosing S1 after the reversal, making perseverative errors. Research suggests that the pigeons are timing the reversal from the start of the session. However, making the reversal unpredictable does not discourage the pigeons from timing. Curiously, pigeons' accuracy improves if one decreases the value of the S2 stimulus relative to the S1 stimulus. Another form of asymmetry between S1 and S2 can be found by varying, over trials, the number of S1 or S2 stimuli. Counterintuitively, if the number of S2 stimuli varies, it results in a large increase in anticipatory errors but little increase in perseverative errors. However, if the number of S1 stimuli varies over trials, it results in a large increase in perseverative errors but no increase in anticipatory errors. These last two effects suggest that in the original midsession reversal task, the pigeons are learning to reject S2 during the first half of each session and learning to reject S1 during the last half of each session. These results suggest that reject learning may also play an important role in the learning of simple simultaneous discriminations.

Midsession reversal learning: Pigeons learn what stimulus to avoid.

The midsession reversal task involves a simple simultaneous discrimination in which, each session, choice of 1 stimulus (S1) is correct for the first 40 trials of each session, and choice of the other stimulus (S2) is correct for the remaining 40 trials. After considerable training with this task, pigeons typically continue to choose S2 too early (making anticipatory errors) and continue choosing S1 for following the reversal (making perseverative errors). Errors can be reduced, however, by decreasing the probability of reinforcement for correct S2 choices or by increasing the response requirement for S2 choices. Increasing the number of S2 stimuli (over trials, 1 S2 stimulus on each trial), however, does not reduce errors. Instead, it results in an increase in anticipatory errors but no change in perseverative errors. In the present experiment, we increased the number of S1 stimuli (over trials, 1 S1 stimulus on each trial) and found an increase in the number of perseverative errors but no change in anticipatory errors. The results suggest that the pigeons acquire this task by learning which stimuli to avoid, rather than which stimuli to choose, although it is also possible that these effects result from attention drawn to the variable stimuli when they are incorrect. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Adventitious Reinforcement of Maladaptive Stimulus Control Interferes with Learning.

Persistent error patterns sometimes develop when teaching new discriminations. These patterns can be adventitiously reinforced, especially during long periods of chance-level responding (including baseline). Such behaviors can interfere with learning a new discrimination. They can also disrupt already learned discriminations, if they re-emerge during teaching procedures that generate errors. We present an example of this process. Our goal was to teach a boy with intellectual disabilities to touch one of two shapes on a computer screen (in technical terms, a simple simultaneous discrimination). We used a size-fading procedure. The correct stimulus was at full size, and the incorrect-stimulus size increased in increments of 10%. Performance was nearly error free up to and including 60% of full size. In a probe session with the incorrect stimulus at full size, however, accuracy plummeted. Also, a pattern of switching between choices, which apparently had been established in classroom instruction, re-emerged. The switching pattern interfered with already-learned discriminations. Despite having previously mastered a fading step with the incorrect stimulus up to 60%, we were unable to maintain consistently high accuracy beyond 20% of full size. We refined the teaching program such that fading was done in smaller steps (5%), and decisions to "step back" to a smaller incorrect stimulus were made after every 5-instead of 20-trials. Errors were rare, switching behavior stopped, and he mastered the discrimination. This is a practical example of the importance of designing instruction that prevents adventitious reinforcement of maladaptive discriminated response patterns by reducing errors during acquisition.

Exclusion performance and learning by exclusion in dogs.

Responding by exclusion is a type of emergent repertoire in which an individual chooses an alternative by the apparent exclusion of other available alternatives. In this case it is possible to respond appropriately to an undefined stimulus (one that has not previously acquired discriminative functions) by excluding the defined alternatives. There is evidence of exclusion in humans and nonhuman animals, although learning as an outcome of exclusion does not always occur. This study aimed to investigate exclusion in visual simple discriminations and learning of new simple discriminations resulting from exclusion in four border collies. Subjects were trained to perform simple simultaneous discriminations between pairs of tridimensional objects, and were then tested for exclusion, novelty control and learning of new simple discriminations. All dogs successfully responded by exclusion, choosing an undefined stimulus displayed with an S-. For three dogs, it was possible to conclude that these previously undefined stimuli acquired S+ functions, documenting learning of new simple discriminations. However, this required up to four exposures to exclusion trials with each pair of stimuli.

Rats' midsession reversal performance: the nature of the response.

The midsession reversal task involves a simple simultaneous discrimination that predictably reverses midway through a session. Under various conditions, pigeons generally both anticipate the reversal and perseverate once it has occurred, whereas rats tend to make very few of either kind of error. In the present research, we investigated the hypothesis that the difference in performance between rats and pigeons is related to the nature of the responses made. We hypothesized that rats could have been better at bridging the intertrial interval by keeping the relevant paw close to the lever while eating, whereas the pigeons had to remove their beak from the response key and insert it into the feeder, thus making it difficult to mediate the response last made. In the present experiment, in successive phases, rats were trained to leverpress or nose-poke on a 40-trial midsession reversal, an 80-trial midsession reversal, and a variable-location reversal. The results showed that the leverpress group acquired the task faster than the nose-poke group, but that both groups reached comparable levels of performance. Thus, the difference in the natures of the responses cannot fully account for the differences in accuracy between rats and pigeons. Additionally, differences in the types of errors made by the two groups suggest that the nature of the response plays different roles in the performance of this task.

EMERGÊNCIA DE CLASSES DE EQUIVALÊNCIA APÓS SEPARAÇÃO E RECOMBINAÇÃO DOS ESTÍMULOS COMPOSTOS UTILIZADOS NO TREINO

Dois estudos ensinaram discriminações de estímulos compostos e avaliaram a emergência de classes de equivalência com dois procedimentos diferentes de teste. Em ambos os estudos, estudantes universitários foram submetidos a treino com discriminações simples simultâneas (DSS) e a emergência de classes de equivalência foi testada utilizando-se tanto um procedimento de DSS quanto de pareamento ao modelo. Os estudos diferiram quanto ao número de classes treinadas/ testadas. No Estudo 1, quatro de nove participantes demonstraram a emergência de relações transitivas e de equivalência. No Estudo 2, os cinco participantes demonstraram a emergência de todas as relações testadas. Não houve diferença nos resultados em função do tipo de teste. Os resultados fornecem suporte empírico para a noção de que elementos de um estímulo composto podem ser separados e recombinados sem que haja ruptura no controle discriminativo. Palavras-chave: Discriminações simples simultâneas, estímulos compostos, relações arbitrárias emergentes, estudantes universitários.

Responding by exclusion in Wistar rats in a simultaneous visual discrimination task.

Responding by exclusion is to select a correct alternative by rejecting other potential alternatives. Studies describe this ability in some mammals and birds. However, this type of performance has not been reported in rodents. The aim of this study was to verify the occurrence of responding by exclusion in Wistar rats after a baseline of simple simultaneous visual discrimination. Six male Wistar learned nose-poking tunnels displaying visual stimuli (projected geometric shapes) in an operant chamber. After establishing the simultaneous discrimination baseline, three probe sessions were conducted. In each session, there was a novelty-control probe (a new stimulus was presented together with a stimulus trained as the S(+)) and an exclusion probe (a second new stimulus was presented simultaneously with a stimulus trained as the S(-)). Only one rat responded to the new stimulus in one of the three novelty probe trials. Four rats responded to the three new stimuli and one responded to the new stimulus in two of the three exclusion probes. One subject responded to the S(-) in all the exclusion probes. Five of the six subjects were therefore able to choose the new stimulus, rejecting stimuli trained as the S(-). This is the first experimental evidence for performance by exclusion in rats.

Discrimination and Reversal Learning by Toddlers Aged 15-23 Months.

Few studies have investigated simple discrimination and discrimination reversal learning by children younger than 2 years. Extant research has shown that teaching discrimination reversals may be challenging with this population. We used social reinforcement and correction procedures to teach simple simultaneous discrimination and discrimination reversal tasks involving three pairs of animal pictures displayed in a paper notebook. Participants were eight typically-developing toddlers aged 15-23 months. All learned at least one simple discrimination/discrimination reversal problem. Four children learned all problems and showed evidence of learning set formation. Perhaps surprisingly, discrimination reversals were sometimes learned more rapidly than original discriminations. The procedures suggest a potentially efficient methodology for investigating more complex aspects of relational learning in toddlers.

Exclusion performance in visual simple discrimination in dogs (Canis familiaris).

based on exclusion have been investigated in different species because of its emergent nature, leading to evidence of rudimentary symbolic behavior in non-verbal organisms. Simple discrimination procedures provide a simple method to investigate exclusion performance, in which each trial consists of the simultaneous presentation of two stimuli, one with a positive function (S+) and one with a negative function (S-). In exclusion probe trials, an undefined stimulus (UnS) is presented with a familiar S - , and choices based on exclusion may lead to choosing the UnS, excluding the previously known S - . Novelty control trials (S + /UnS) are also conducted to assess the possible preference for the UnS. In this case, if performance is not controlled by novelty, then the subjects must choose the S + and not the UnS. The present study investigated exclusion performance in visual simple simultaneous discrimination tasks in eight dogs. The results indicated that seven of eight dogs showed evidence of exclusion performance (p < .05). These findings corroborate the literature that shows that dogs are capable of responding by exclusion, suggesting that potentially symbolic behavior may rely on basic behavioral learning and conditioning principles.

Assessing restricted stimulus control in typically developing preschool children and bees (Melipona quadrifasciata).

study established a simple simultaneous discrimination between a pair of two-element compound visual stimuli in children (Experiment 1) and bees (Melipona quadrifasciata, Experiment 2). The contingencies required discriminative control by the compound and the question was whether the accurate stimulus control reached at this level would hold for each individual element of the compound. After baseline reached stability, probe trials assessed stimulus control by each single element of both S+ and S-. Average data showed that children (Exp. 1) tended to show stimulus control by a single element of the S+ compound. In Experiment 2 three of four bees showed stimulus control by both elements of S+ and did not respond or responded only infrequently to the elements of the S-. The children's decline in discrimination accuracy in probe trials, along with its maintenance during the baseline, replicated previous findings showing the development of restricted stimulus control (RSC). The precise stimulus control shown by the bees indicated that all elements correlated with reinforcement acquired stimulus control over their behavior; this confirms the extensive literature on visual discriminative learning in bees, but due to the small number of subjects it is premature to say that bees do not develop RSC.

Análise do Controle de Estímulos resultante da Manipulação do número de escolhas em Treino Discriminativo com Macacos-Prego (Sapajus Sp.)

Estudos anteriores avaliaram o efeito da apresentação de múltiplas cópias de S- em treino de discriminação simples simul¬tânea S+/S-. O presente estudo avaliou se, nesse tipo de procedimento, algum controle pelas características nominais dos estímulos se desenvolve, além do controle pela singularidade do S+ (Experimento I). Adicionalmente, o presente estudo avaliou qualitativamente as relações de controle produzidas neste tipo de procedimento (Experimento II). No Experimento I, macacos-prego (Sapajus sp.) foram submetidos a treino discriminativo com três tipos diferentes de tentativas (duas, quatro e nove escolhas). Um teste de controle de estímulos avaliou se o repertório aprendido podia ser mantido quando os estímulos utilizados nos três tipos de tentativa eram apre¬sentados na forma de duas escolhas. Os resultados apontam claramente controle pelas características nominais dos estímulos. No Ex¬perimento II, o procedimento de máscara foi utilizado para identificar as relações de controle (por seleção e/ou rejeição) desenvolvidas. Os resultados mostram sólido controle por rejeição para ambos os sujeitos, com controle por seleção também presente para um dos sujeitos. O presente trabalho contribui no sentido de aprofundar a análise do controle de estímulos em estudos sobre a manipulação do número de escolhas em treino discriminativo.

Simple Successive Discrimination and Functional Class Formation in Preschool Children

The present study evaluated the effectiveness of a simple successive (go/ no-go) discrimination procedure in producing functional class formation as a systematic replication of a previous study with simple simultaneous discrimination. Five preschool children learned 3 simple discriminations and were given repeated reversal training with all 6 stimuli simultaneously. Four of these children learned a fourth discrimination and a new series of reversals with 8 stimuli. Rapid reversals (learning set) occurred with 6 stimuli in 3 children and 8 stimuli in 4 children. Two children presented performance compatible with functional class formation. The results were similar to those reported in the previous study. Similar to the simultaneous procedure, the successive procedure effectively generated functional class formation with some, but not all, of the participants. The occurrence of errors inherent to the reversal procedure may be a source of variability. Future research should investigate other strategies to promote stimulus class formation on the basis of shared discriminative functions.

Pigeons’ use of cues in a repeated five-trial-sequence, single-reversal task

We studied behavioral flexibility, or the ability to modify one's behavior in accordance with the changing environment, in pigeons using a reversal-learning paradigm. In two experiments, each session consisted of a series of five-trial sequences involving a simple simultaneous color discrimination in which a reversal could occur during each sequence. The ideal strategy would be to start each sequence with a choice of S1 (the first correct stimulus) until it was no longer correct, and then to switch to S2 (the second correct stimulus), thus utilizing cues provided by local reinforcement (feedback from the preceding trial). In both experiments, subjects showed little evidence of using local reinforcement cues, but instead used the mean probabilities of reinforcement for S1 and S2 on each trial within each sequence. That is, subjects showed remarkably similar behavior, regardless of where (or, in Exp. 2, whether) a reversal occurred during a given sequence. Therefore, subjects appeared to be relatively insensitive to the consequences of responses (local feedback) and were not able to maximize reinforcement. The fact that pigeons did not use the more optimal feedback afforded by recent reinforcement contingencies to maximize their reinforcement has implications for their use of flexible response strategies under reversal-learning conditions.

DISCRIMINAÇÕES SIMPLES SIMULTÂNEAS E RESPONDER RELACIONAL SIMPLE SIMULTANEOUS DISCRIMINATION AND RELATIONAL RESPONDING

O presente trabalho apresentou um procedimento de treino discriminativo alternativo às propostas atuais sobre responder relacional e emergência de relações entre estímulos. Participaram 17 alunos do curso de Psicologia e 16 alunos e um professor do curso de Engenharia de Telecomunicações. Os participantes foram expostos a treinos de discriminações simples simultâneas com estímulos compostos. Após o treino, os estímulos foram decompostos e relações aprendidas e novas entre estímulos foram testadas utilizando-se um procedimento de emparelhamento ao modelo. Dez alunos do curso de Engenharia e dois do curso de Psicologia atingiram o critério de aprendizagem nos treinos. Sete desses 12 participantes apresentaram emergência de novas relações nos testes. O procedimento de treino mostrou-se viável para o estudo do responder relacional e emergência de relações entre estímulos. Os resultados sugerem ainda uma reflexão sobre os conceitos de discriminação simples e discriminação condicional e sobre a história pré-experimental dos participantes como uma variável relevante para o estudo do comportamento simbólico. Palavras-chave: discriminações simples simultâneas, responder relacional, emergência de relações entre estímulos

Hippocampal lesions can enhance discrimination learning despite normal sensitivity to interference from incidental information

Spatial properties of stimuli are sometimes encoded even when incidental to the demands of a particular learning task. Incidental encoding of spatial information may interfere with learning by (i) causing a failure to generalize learning between trials in which a cue is presented in different spatial locations and (ii) adding common spatial features to stimuli that predict different outcomes. Hippocampal lesions have been found to facilitate acquisition of certain tasks. This facilitation may occur because hippocampal lesions impair incidental encoding of spatial information that interferes with learning. To test this prediction mice with lesions of the hippocampus were trained on appetitive simple simultaneous discrimination tasks using inserts in the goal arms of a T-maze. It was found that hippocampal lesioned mice were facilitated at learning the discriminations, but they were sensitive to changes in spatial information in a manner that was similar to control mice. In a second experiment it was found that both control and hippocampal lesioned mice showed equivalent incidental encoding of egocentric spatial properties of the inserts, but both groups did not encode the allocentric information. These results demonstrate that mice show incidental encoding of egocentric spatial information that decreases the ability to solve simultaneous discrimination tasks. The normal egocentric spatial encoding in hippocampal lesioned mice contradicts theories of hippocampal function that suggest that the hippocampus is necessary for incidental learning per se, or is required for modulating stimulus representations based on the relevancy of information. The facilitated learning suggests that the hippocampal lesions can enhance learning of the same qualitative information as acquired by control mice. © 2011 Wiley Periodicals, Inc.

Topography of Responses in Conditional Discrimination Influences Formation of Equivalence Classes

The effects of response topography on stimulus class formation were studied in two experiments. In Experiment 1, 32 college students were assigned to 2 response topographies and 2 stimulus sets, in a 2 × 2 design. Students selected stimuli by either moving a mouse to place an arrow-shaped cursor on the stimulus or pressing a key corresponding to stimulus location. After they learned conditional discriminations EF, DE, CD, BC, and AB and a simple simultaneous discrimination, tests for class formation were conducted. The number of students showing class formation was larger for the group using the mouse. Stimulus set had no effect. Experiment 2 included probes for controlling relations in the baseline and showed that the response topography using the mouse increases the probability of sample-S+ relations, thus increasing the probability of class formation.

A NOVEL METHOD FOR TEACHING THE FIRST INSTANCES OF SIMPLE DISCRIMINATION TO NONVERBAL CHILDREN WITH AUTISM IN A LABORATORY ENVIRONMENT.

A novel method for initiating discrimination training with nonverbal children combines a delayed S+ procedure that requires children to refrain from responding to either of 2 physically different choice stimuli until a prompt stimulus is added onto 1 of the choices, and a delayed prompting procedure that presents the same 2-choice stimulus display, but stimuli are initially added onto both choices. After a short delay, the added stimulus on the S- is removed, and the choice of the S+ is thus prompted. If the children learn to observe and respond to the defining features of the S+ choice stimulus, then they may respond to the S+ prior to the added-stimulus removal. Implementation was successful with 8 nonverbal children who had not previously exhibited simple simultaneous discrimination, suggesting a useful methodology for initiating discrimination training with populations for whom verbal instruction is ineffective.

Advances in endophenotyping schizophrenia

The search for the genetic architecture of schizophrenia has employed multiple, often converging strategies. One such strategy entails the use of tracing the heritability and neurobiology of endophenotypes. Endophenotypes are quantifiable traits not visible to the eye, which are thought to reflect an intermediate place on the path from genes to disorder. Endophenotype abnormalities in domains such as neurophysiology or neurocognition occur in schizophrenia patients as well as their clinically "unaffected" relatives, and reflect polymorphisms in the DNA of schizophrenia spectrum subjects which create vulnerability to developing schizophrenia. By identifying the single nucleotide polymorphisms (SNPs) associated with endophenotypes in schizophrenia, psychiatric neuroscientists can select new strong inference based molecular targets for the treatment of schizophrenia.