Simple Discrimination Task Research Articles

Implementing portable touchscreen-setups to enhance cognitive research and enrich zoo-housed animals

To understand the evolutionary development of cognition, comparing the cognitive capacities of different animal species is essential. However, getting access to various species with sufficient sample sizes can be very challenging. Zoos, housing large ranges of animal taxa, would offer ideal research environments, but zoo-based studies on cognition are still rare. The use of touchscreen-computers to explore the cognitive abilities of nonhuman animals has shown to be highly applicable, and simultaneously offers new enrichment possibilities for captive animals. To facilitate zoo-based research, I here illustrate the assembly and usage of newly developed touchscreen-computer-systems (Zoo-based Animal-Computer-Interaction System, ZACI), which can be used in various zoo environments and, importantly, with different taxa (e.g. primates, birds). The developed setups are portable, can be attached to various mesh sizes, and do not need any external power supply while being used. To evaluate the usability of the ZACI, they have been tested with experimentally naive subjects of three great ape species (orang-utans, chimpanzees, gorillas) housed at Zoo Heidelberg, Germany, demonstrating to be animal-proof, easy to handle, and of great interest to the animals. Animals could be tested within their social group, as each subject had access to its own device during testing. To support the implementation of touchscreen-setups at other facilities, I also illustrate the training procedure and present first data on the apes’ performance in a simple object discrimination task. Portable touchscreen-setups offer the great possibility to enhance collaboration between zoos and researchers, allow a standardisation of methods, and improve data collection.

Decoupling sensory from decisional choice biases in perceptual decision making.

The contribution of sensory and decisional processes to perceptual decision making is still unclear, even in simple perceptual tasks. When decision makers need to select an action from a set of balanced alternatives, any tendency to choose one alternative more often-choice bias-is consistent with a bias in the sensory evidence, but also with a preference to select that alternative independently of the sensory evidence. To decouple sensory from decisional biases, here we asked humans to perform a simple perceptual discrimination task with two symmetric alternatives under two different task instructions. The instructions varied the response mapping between perception and the category of the alternatives. We found that from 32 participants, 30 exhibited sensory biases and 15 decisional biases. The decisional biases were consistent with a criterion change in a simple signal detection theory model. Perceptual decision making, thus, even in simple scenarios, is affected by sensory and decisional choice biases.

Towards Establishing Age-Related Cortical Plasticity on the Basis of Somatosensation

Age-related somatosensory processing appears to remain intact where tasks engage centrally- as opposed to peripherally-mediated mechanisms. This distinction suggests that insight into alterations in neural plasticity could be derived via metrics of vibrotactile performance. Such an approach could be used to support the early detection of global changes in brain health but current evidence is limited. Knowledge of the precise conditions in which older adults are expected to sustain somatosensory performance is largely unknown. For this purpose, the study aimed to characterize age-related performance on tactile detection and discrimination-based tests. Accordingly, a group of young and older adult participants took part in simple reaction time and amplitude discrimination tasks. Participants' ability to distinguish between stimuli on the basis of amplitude was assessed with and without dual-site adaptation, which has been proposed to refine cortical responses and improve behavioral performance. The results show that while older adults exhibited significantly prolonged (p < .001, d = 1.116) and more variable (p = .022, d = 0.578) information processing speed compared to young adults, they were able to achieve similar scores in baseline discrimination (p = .179, d = 0.336). We also report, for the first time, that older adults displayed similar performance improvements to young adults, under conditions of dual-site adaptation (p = .948, d = 0.016). The findings support the argument that centrally-mediated mechanisms remain intact in the ageing population. Accordingly, dual-site adaptation data provide compelling new evidence of somatosensation in ageing that will contribute towards the development of an assessment tool to ascertain pre-clinical, age-related changes in the status of cortical function.

A Domain-General Sense of Confidence in Children

Our minds constantly evaluate the confidence in what we see, think, and remember. Previous work suggests that confidence is a domain-general currency in adulthood, unifying otherwise independent sensory and perceptual representations. Here, we test whether children also possess a domain-general sense of confidence over otherwise independent perceptual dimensions. Six- to 9-year-olds completed either three simple perceptual discrimination tasks—a number task (“Which group has more dots?”), an area task (“Which blob is bigger?”), and an emotions task (“Which face is happier?”)—or three relative confidence tasks, selecting which of two trials they are more confident on. We find that while children’s discrimination performance across the three tasks was independent and constituted three separate factors, children’s confidence in each of three dimensions was strongly correlated and constituted only a single factor. Our results suggest that confidence is a domain-general currency even in childhood, providing a mechanism by which disparate perceptual representations could be integrated.

Inter-trial variability in brain activity as an indicator of synergistic effects of HIV-1 and drug abuse

BackgroundThe objective of this investigation was to detect evidence of the synergism in the effects of HIV-1 and drug abuse on brain function that has been hypothesized but rarely shown. The investigation incorporated several noteworthy improvements in the approach. It used urine toxicology tests to exclude participants complicated by recent methadone use and illicit drug use. Also, it defined drug abuse on a scale that considered symptom severity. Most importantly, it examined inter-trial variability in brain activity as a potentially more sensitive indicator of group differences and functional impairment than the across-trial average. Methods173 participants were assigned to groups defined by their HIV-1 serostatus and Drug Abuse Screening Test score (DAST < vs. > = 6). They completed a simple letter discrimination task including rare target and rare nontarget stimuli. Event-related electroencephalographic responses and key press responses were measured on each trial. During a separate assessment, posturographic measures were recorded. ResultsThe inter-trial standard deviation of P300-like activity was superior to the mean amplitude of this activity in differentiating the groups. Unlike the mean, it revealed synergistic statistical effects of HIV and drug abuse. It also correlated significantly with static ataxia. ConclusionsInter-trial variability in P300-like activity is a useful marker for detecting subtle and episodic disruptions in brain function. It demonstrates greater sensitivity than the mean amplitude for detecting differences across groups. Also, as a putative indicator of a disruption in the attentional monitoring of behavior, it predicts subtle impairments in gross motor function.

High-Speed Videography Reveals How Honeybees Can Turn a Spatial Concept Learning Task Into a Simple Discrimination Task by Stereotyped Flight Movements and Sequential Inspection of Pattern Elements.

Honey bees display remarkable visual learning abilities, providing insights regarding visual information processing in a miniature brain. It was discovered that bees can solve a task that is generally viewed as spatial concept learning in primates, specifically the concept of “above” and “below.” In these works, two pairs of visual stimuli were shown in the two arms of a Y-maze. Each arm displayed a “referent” shape (e.g., a cross, or a horizontal line) and a second geometric shape that appeared either above or below the referent. Bees learning the “concept of aboveness” had to choose the arm of the Y-maze in which a shape–any shape–occurred above the referent, while those learning the “concept of belowness” had to pick the arm in which there was an arbitrary item beneath the referent. Here, we explore the sequential decision-making process that allows bees to solve this task by analyzing their flight trajectories inside the Y-maze. Over 368 h of high-speed video footage of the bees' choice strategies were analyzed in detail. In our experiments, many bees failed the task, and, with the possible exception of a single forager, bees as a group failed to reach significance in picking the correct arm from the decision chamber of the maze. Of those bees that succeeded in choosing correctly, most required a close-up inspection of the targets. These bees typically employed a close-up scan of only the bottom part of the pattern before taking the decision of landing on a feeder. When rejecting incorrect feeders, they repeatedly scanned the pattern features, but were still, on average, faster at completing the task than the non-leaners. This shows that solving a concept learning task could actually be mediated by turning it into a more manageable discrimination task by some animals, although one individual in this study appeared to have gained the ability (by the end of the training) to solve the task in a manner predicted by concept learning.

What happens to an individual visual working memory representation when it is interrupted?

This study tested the hypothesis that even the simplest cognitive tasks require the storage of information in working memory (WM), distorting any information that was previously stored in WM. Experiment 1 tested this hypothesis by requiring observers to perform a simple letter discrimination task while they were holding a single orientation in WM. We predicted that performing the task on the interposed letter stimulus would cause the orientation memory to become less precise and more categorical compared to when the letter was absent or when it was present but could be ignored. This prediction was confirmed. Experiment 2 tested the modality specificity of this effect by replacing the visual letter discrimination task with an auditory pitch discrimination task. Unlike the interposed visual stimulus, the interposed auditory stimulus produced little or no disruption of WM, consistent with the use of modality-specific representations. Thus, performing a simple visual discrimination task, but not a simple auditory discrimination task, distorts information about a single feature being maintained in visual WM. We suggest that the interposed task eliminates information stored within the focus of attention, leaving behind a WM representation outside the focus of attention that is relatively imprecise and categorical.

I121] Model observers applied to quality control in computed tomography

Model observers are mathematical algorithms that can include different aspects of the human visual system and aim to reproduce human performance for simple detection tasks. Their use has extended in different medical imaging modalities, such as mammography, computed tomography (CT) and nuclear medicine among others, in the past few years. Several model observers have shown good correlation with human observers for simple detection and discrimination tasks in image quality phantoms with uniform backgrounds. Some model observers have been used by CT manufacturers to obtain clearance for their image quality claims, in particular for low contrast detectability (LCD), in the USA. LCD is frequently assessed in CT by human observers scoring the visibility of simple objects (such as disks) of different contrast and size in phantom images. These studies might be biased as, in general, the observer knows the distribution of the objects in the phantom beforehand. A great inter- and intra-observer variability might also appear. The models that will be studied in the course are: the non-prewhitening matched filter with an eye filter (NPWE) and the channelized Hotelling observer (CHO). The NPWE model includes a mathematical implementation of the contrast sensitivity function (CSF) of the human eye. There exist different published functions for the CSF based on human observer studies. The CHO model includes channels that can have different shapes (Gabor, Laguerre-Gauss, difference of gaussians…) depending on the target object; the channels aim to mimic the neurons triggering in the human visual cortex. Different aspects the implementation of model observers in image quality assessment, in particular in CT will be explored in this refresher course. Among them, how to choose the task, how to implement a model observer and its limitations, and also a short introduction on how to validate the model results with human observer studies. Practical examples about the use of these models in routine quality control, for example for low contrast detectability assessment, will be shown. Tips about how to start implementing model observers, in particular with freeware (imageJ), will be shared.

The opportunity cost of time modulates cognitive effort

A spate of recent work demonstrates that humans seek to avoid the expenditure of cognitive effort, much like physical effort or economic resources. Less is clear, however, about the circumstances dictating how and when people decide to expend cognitive effort. Here we adopt a popular theory of opportunity costs and response vigor and to elucidate this question. This account, grounded in Reinforcement Learning, formalizes a trade-off between two costs: the harder work assumed necessary to emit faster actions and the opportunity cost inherent in acting more slowly (i.e., the delay that results to the next reward and subsequent rewards). Recent work reveals that the opportunity cost of time—operationalized as the average reward rate per unit time, theorized to be signaled by tonic dopamine levels, modulates the speed with which a person responds in a simple discrimination tasks. We extend this framework to cognitive effort in a diverse range of cognitive tasks, for which 1) the amount of cognitive effort demanded from the task varies from trial to trial and 2) the putative expenditure of cognitive effort holds measureable consequences in terms of accuracy and response time. In the domains of cognitive control, perceptual decision-making, and task-switching, we found that subjects tuned their level of effort exertion in accordance with the experienced average reward rate: when the opportunity cost of time was high, subjects made more errors and responded more quickly, which we interpret as a withdrawal of cognitive effort. That is, expenditure of cognitive effort appeared to be modulated by the opportunity cost of time. Further, and consistent with our account, the strength of this modulation was predicted by individual differences in efficacy of cognitive control. Taken together, our results elucidate the circumstances dictating how and when people expend cognitive effort.

Do Event-Related Evoked Potentials Reflect Apathy Tendency and Motivation?

Apathy is a mental state of diminished motivation. Although the reward system as the foundation of the motivation in the human brain has been studied extensively with neuroimaging techniques, the electrophysiological correlates of motivation and apathy have not been fully explored. Thus, in 14 healthy volunteers, we examined whether event-related evoked potentials (ERP) obtained during a simple number discrimination task with/without rewards reflected apathy tendency and a reward-dependent tendency, which were assessed separately using the apathy scale and the temperament and character inventory (TCI). Participants were asked to judge the size of a number, and received feedback based on their performance in each trial. The P3 amplitudes related to the feedback stimuli increased only in the reward condition. Furthermore, the P2 amplitudes related to the negative feedback stimuli in the reward condition had a positive correlation with the reward-dependent tendency in TCI, whereas the P3 amplitudes related to the positive feedback stimuli had a negative correlation with the apathy score. Our result suggests that the P2 and P3 ERPs to reward-related feedback stimuli are modulated in a distinctive manner by the motivational reward dependence and apathy tendency, and thus the current paradigm may be useful for investigating the brain activity associated with motivation.

Impaired Attentional Set-Shifting Performance after Exposure to 5 cGy of 600 MeV/n 28Si Particles.

Astronauts on deep space missions will be required to work more autonomously than on previous missions, and thus their ability to perform executive functions could be critical to mission success. One of the most common measures of executive function in humans is the ability to perform attentional set shifting, which requires contributions from working memory, discrimination, reversal learning, attentional set shifting and attention. Rodent attentional set shifting assays require rats to form an association between the presence of the food reward and an associative cue, which is either the digging media or the scent that is placed in the bowl; by altering the combination of scent and digging media, progressively more complex cognitive processes can be tested. In this study, we have determined the effect that exposure to 5-20 cGy of 600 MeV/n 28Si particles has on the ability of male retired breeder Wistar rats to perform attentional set shifting at three months postirradiation. All doses of Si resulted in a significant impairment in the ability of the rats to perform the first and most simple step of the ATSET assay, the simple discrimination (SD) task. If astronauts were to experience HZE-induced SD impairments, they would be unable to identify key factors to successfully resolve a situation. Performance in at least one other component of the ATSET test was impaired at all doses studied, however, these varied according to the dose. Compared with our previous studies using 1 GeV/n 56Fe and 48Ti particles, 600 MeV/n 28Si ions impaired attentional set-shifting performance at lower doses than the heavier ions. However, when the effect of isofluences of the three HZE ions were compared, there were no significant differences in the severity of the impaired performance; there were, however, ion-specific decrements in the ability of rats to perform within the various stages of the test. This study further supports the notion that "mission-relevant" doses of HZE particles (<20 cGy) can impair certain aspects of attentional set-shifting performance in retired breeder rats, but there may be some ion-specific changes in the specific cognitive domains impaired.

Adapted wavelet transform improves time-frequency representations: a study of auditory elicited P300-like event-related potentials in rats

Objective. Active auditory oddball paradigms are simple tone discrimination tasks used to study the P300 deflection of event-related potentials (ERPs). These ERPs may be quantified by time-frequency analysis. As auditory stimuli cause early high frequency and late low frequency ERP oscillations, the continuous wavelet transform (CWT) is often chosen for decomposition due to its multi-resolution properties. However, as the conventional CWT traditionally applies only one mother wavelet to represent the entire spectrum, the time-frequency resolution is not optimal across all scales. To account for this, we developed and validated a novel method specifically refined to analyse P300-like ERPs in rats. Approach. An adapted CWT (aCWT) was implemented to preserve high time-frequency resolution across all scales by commissioning of multiple wavelets operating at different scales. First, decomposition of simulated ERPs was illustrated using the classical CWT and the aCWT. Next, the two methods were applied to EEG recordings obtained from prefrontal cortex in rats performing a two-tone auditory discrimination task. Main results. While only early ERP frequency changes between responses to target and non-target tones were detected by the CWT, both early and late changes were successfully described with strong accuracy by the aCWT in rat ERPs. Increased frontal gamma power and phase synchrony was observed particularly within theta and gamma frequency bands during deviant tones. Significance. The study suggests superior performance of the aCWT over the CWT in terms of detailed quantification of time-frequency properties of ERPs. Our methodological investigation indicates that accurate and complete assessment of time-frequency components of short-time neural signals is feasible with the novel analysis approach which may be advantageous for characterisation of several types of evoked potentials in particularly rodents.

Eurasian jays do not copy the choices of conspecifics, but they do show evidence of stimulus enhancement.

Corvids (birds in the crow family) are hypothesised to have a general cognitive tool-kit because they show a wide range of transferrable skills across social, physical and temporal tasks, despite differences in socioecology. However, it is unknown whether relatively asocial corvids differ from social corvids in their use of social information in the context of copying the choices of others, because only one such test has been conducted in a relatively asocial corvid. We investigated whether relatively asocial Eurasian jays (Garrulus glandarius) use social information (i.e., information made available by others). Previous studies have indicated that jays attend to social context in their caching and mate provisioning behaviour; however, it is unknown whether jays copy the choices of others. We tested the jays in two different tasks varying in difficulty, where social corvid species have demonstrated social information use in both tasks. Firstly, an object-dropping task was conducted requiring objects to be dropped down a tube to release a food reward from a collapsible platform, which corvids can learn through explicit training. Only one rook and one New Caledonian crow have learned the task using social information from a demonstrator. Secondly, we tested the birds on a simple colour discrimination task, which should be easy to solve, because it has been shown that corvids can make colour discriminations. Using the same colour discrimination task in a previous study, all common ravens and carrion crows copied the demonstrator. After observing a conspecific demonstrator, none of the jays solved the object-dropping task, though all jays were subsequently able to learn to solve the task in a non-social situation through explicit training, and jays chose the demonstrated colour at chance levels. Our results suggest that social and relatively asocial corvids differ in social information use, indicating that relatively asocial species may have secondarily lost this ability due to lack of selection pressure from an asocial environment.

Effects of absolute luminance and luminance contrast on visual discrimination in low mesopic environments.

Recent research revealed considerable decline in visual perception under low luminance conditions. However, systematic studies on how visual performance is affected by absolute luminance and luminance contrast under low mesopic conditions (<0.5cd/m2) is lacking. We examined performance in a simple visual discrimination task under low mesopic luminance conditions in three experiments in which we systematically varied base luminance and luminance contrast between stimulus and background. We further manipulated eccentricity of the stimuli because of known rods and cones gradients along the retina. We identified a "deficiency window" for performance as measured by d' when luminance was < 0.06cd/m2 and luminance contrast as measured by the luminance ratio between stimulus and background was below < 1.7. We further calculated performance-based luminance as well as contrast efficiency functions for reaction times (RTs). These power functions demonstrate the contrast asymptote needed to decrease RTs and how such a decrease can be achieved given various combinations of absolute luminance and luminance contrast manipulations. Increased eccentricity resulted in slower RTs indicative of longer scan distances. Our data provide initial insights to performance-based efficiency functions in low mesopic environments that are currently lacking and to the physical mechanisms being utilized for visual perception in these extreme environments.

Visual interference disrupts visual knowledge

Abstract We show that visual interference impairs people’s ability to make use of visual knowledge. These results provide strong evidence that making use of stored visual knowledge—long-term memory of what things look like—depends on perceptual mechanisms. In the first set of studies, we show that presenting visual noise patterns during or after hearing a verbal cue greatly reduces the effectiveness of the cue on a simple visual discrimination task. In the second experiment, participants were tasked with answering questions about visual features of familiar objects, e.g., verifying that tables have flat surfaces. Accuracy in answering visual, but not encyclopedic questions was reduced when viewing colorful noise patterns. This result is most parsimoniously explained by positing that judgments required activation of visual representations that were being interfered with when viewing irrelevant patterns. Although much of our conceptual knowledge may abstract away from perceptual details, knowledge of what things look like appears to be represented in a visual format.

ASSESSMENT OF LEARNING AND MEMORY IN THE CVN MOUSE MODEL OF ALZHEIMER’S DISEASE IN AUTOMATED TOUCH SCREEN CHAMBERS

According to previously published data and internal model validation, the CVN mouse model of AD exhibits cognitive impairments in contextual fear conditioning, Barnes maze and radial arm water maze most prominently at 9–12 months of age. To determine if impaired learning can be detected at an earlier age, we evaluated their cognitive performance by using a touch screen operant platform (Horner et al., 2013), which is similar to computerized CANTAB testing widely used in clinical setting. Cohorts of 4–5-month old male CVN (APPSDI/NOS2 knockout) and associated wild type (WT) mice were obtained from Charles River (Sulzfeld, Germany). Following acclimatization, animals were introduced to a restricted diet throughout the study period. Testing was conducted in Bussey-Saksida mouse touch screen chambers (Campden Instruments, Loughborough, UK). Mice were trained to develop screen-touching behavior using a 5-stage pretraining algorithm. Thereafter, they were tested in their ability to visually discriminate alternative black and white “lines-grid” stimuli on the touch screen. In order to test cognitive flexibility, the task of reversal of the acquired visual discrimination was implemented by switching the contingencies used in the visual discrimination test. During pretraining, CVN mice and WT mice required similar number of sessions to achieve the pretraining criterion. Furthermore, the majority of mice successfully acquired visual discrimination within 20 days, again without significant differences in the number of sessions required to reach the discrimination criterion between CVN and WT mice. We found that CVN mice did not exhibit gross cognitive impairment at 5–6 months of age and could learn a simple visual discrimination task at a rate comparable to that of WT mice. This is in line with the lack of deficits previously reported in other cognitive assays at comparable ages. However, CVN mice did demonstrate a slower rate of reversal learning at these ages. Further exploration of this slowed reversal learning phenotype is planned using this highly translatable touch screen approach in order to identify deficits in other touch screen tasks at an early age, but also at later ages, when the AD-related phenotypes are more prominent in terms of brain pathology and behavioral readouts.

Perceptual memory needs slow-wave sleep

Sleep and Memory We know little about the mechanisms by which the brain consolidates nondeclarative (perceptual) memories. In a series of behavioral, optogenetic, and electrophysiological experiments, Miyamoto et al. show that coordinated neuronal information flow during sleep is required for perceptual memory formation. Activity spreading from the secondary motor area (brain area M2) to the primary sensory region S1 is necessary for this particular kind of memory consolidation. Disturbing this coordinated input during slow-wave sleep immediately after memory acquisition prevented mice from learning a simple texture discrimination task. Science , this issue p. [1315][1] [1]: /lookup/doi/10.1126/science.aaf0902

Top-down cortical input during NREM sleep consolidates perceptual memory.

During tactile perception, long-range intracortical top-down axonal projections are essential for processing sensory information. Whether these projections regulate sleep-dependent long-term memory consolidation is unknown. We altered top-down inputs from higher-order cortex to sensory cortex during sleep and examined the consolidation of memories acquired earlier during awake texture perception. Mice learned novel textures and consolidated them during sleep. Within the first hour of non-rapid eye movement (NREM) sleep, optogenetic inhibition of top-down projecting axons from secondary motor cortex (M2) to primary somatosensory cortex (S1) impaired sleep-dependent reactivation of S1 neurons and memory consolidation. In NREM sleep and sleep-deprivation states, closed-loop asynchronous or synchronous M2-S1 coactivation, respectively, reduced or prolonged memory retention. Top-down cortical information flow in NREM sleep is thus required for perceptual memory consolidation.

Comparing species decisions in a dichotomous choice task: adjusting task parameters improves performance in monkeys.

In comparative psychology, both similarities and differences among species are studied to better understand the evolution of their behavior. To do so, we first test species in tasks using similar procedures, but if differences are found, it is important to determine their underlying cause(s) (e.g., are they due to ecology, cognitive ability, an artifact of the study, and/or some other factor?). In our previous work, primates performed unexpectedly poorly on an apparently simple two-choice discrimination task based on the natural behavior of cleaner fish, while the fish did quite well. In this task, if the subjects first chose one of the options (ephemeral) they received both food items, but if they chose the other (permanent) option first, the ephemeral option disappeared. Here, we test several proposed explanations for primates' relatively poorer performance. In Study 1, we used a computerized paradigm that differed from the previous test by removing interaction with human experimenters, which may be distracting, and providing a more standardized testing environment. In Study 2, we adapted the computerized paradigm from Study 1 to be more relevant to primate ecology. Monkeys' overall performance in these adapted tasks matched the performance of the fish in the original study, showing that with the appropriate modifications they can solve the task. We discuss these results in light of comparative research, which requires balancing procedural similarity with considerations of how the details of the task or the context may influence how different species perceive and solve tasks differently.

DISCRIMINAÇÃO SIMPLES E COMPORTAMENTO CONCEITUAL DE POSIÇÃO: INFLUÊNCIA DE DIFERENTES TIPOS DE TREINO

Comportamento conceitual envolve o estabelecimento de classes de estímulos com discriminação interclasses e generalização intraclasse. Esta pesquisa verificou a relação entre o tipo de modificação dos estímulos nos treinos discriminativos e a aquisição de discriminações e de comportamento conceitual de posição. Quinze crianças de 4- 6 anos realizaram tarefas de discriminação simples de posição. Três condições experimentais com treino discriminativo diferente (modificação gradual – MG, múltiplos exemplares – ME e sem modificação - SM dos estímulos utilizados no treino) foram realizadas com todas as crianças. Os participantes deveriam selecionar, em cada condição, o estímulo cujo elemento relacional se localizava dentro, em cima ou à esquerda do elemento de referência. Os treinos foram intercalados com um teste de comportamento conceitual que apresentava estímulos treinados e novos que se diferenciavam apenas com relação à dimensão crítica. Resultados do treino mostraram altos escores nas três condições e menos erros com o Treino MG. Nos testes de comportamento conceitual, desempenhos acima do acaso foram obtidos apenas após o Treino SM. A modificação gradual de estímulos e a utilização de múltiplos exemplares reduziram os erros nos treinos e facilitaram o estabelecimento de discriminações entre estímulos treinados. O treino discriminativo SM com diversas tentativas com os pares de estímulos finais, que diferem apenas na dimensão relevante, produziu comportamento conceitual. Combinar os procedimentos parece, portanto, necessário para acelerar a aquisição das discriminações, prevenir subprodutos dos erros e para gerar controle de estímulos pelas dimensões relevantes. Palavras-chave: aprendizagem sem erro, modelagem de controle de estímulos, múltiplos exemplares, tentativa- e-erro, discriminação de posição, pré-escolares.