Initial Discrimination Training Research Articles

Motivating operations as contexts for operant discrimination training and testing

Two groups of mice were exposed to stimulus discrimination training and testing under different motivational conditions to study interactions between motivating operations (MOs) during initial discrimination training and MOs when performance is tested following training. One group received all discrimination training sessions under 24-h food deprivation while the other received all sessions under 0-h food deprivation. The number of responses allowed during discrimination training sessions was limited such that the two groups experienced the same number of response-outcome contingencies. The groups then received two post-discrimination training tests: one conducted under 24-h food deprivation and the other conducted under 0-h food deprivation. Results indicated no difference between groups in terms of discrimination ratio. However, subjects trained under 24-h deprivation made more responses in the 24-h test, while subjects trained under 0-h deprivation made more responses in the 0-h test. These results are discussed in terms of motivational state-dependent learning.

The effect of learning on heart rate and behavior of European starlings (Sturnus vulgaris).

Wild-caught European starlings (Sturnus vulgaris) were exposed to a learning task to determine whether heart rate (HR) and behavior responses to the learning activated the sympathetic nervous system. Birds learned to discriminate between images of opposite convexity (concave and convex) based on shading cues in a closed economy (food only available through task completion). Once learned, the task was changed in three ways: (a) manipulating the angle and shape of the image; (b) altering the availability of the task; and (c) reversing the positive stimulus. HR, used as an index of catecholamine release, was measured during each change to determine whether having to alter previously established behaviors to learn new behaviors elicited a sympathetic response. Starlings decreased their HR during the initial discrimination training and did not alter their HR when presented with modified images or when the positive stimulus was reversed. However, HR increased when the task became unavailable and decreased upon its return, suggesting that preventing task performance was perceived as stressful. Birds also modified their behavior when tasks were changed. The number of trials per minute decreased during the reversal treatment, as did the success rate, suggesting that starlings may try to conserve energy when access to food diminishes. This is also supported by the decrease in perch hops per minute when the task was unavailable and the subsequent increase upon its return. Overall, these results suggest that learning per se does not activate the sympathetic nervous system and, therefore, is not a stressor for wild birds.

Open field, panel length discrimination by homing pigeons (Columba livia)

Pigeons were trained to find a food reward in a square environmental space where two opposing walls had longer panels attached to them, and the other two opposing walls had shorter panels attached to them. Magnitude discrimination theory would lead to the prediction that there would be asymmetrical discriminative performance between experimental groups; rewarded associations with longer panels were expected to yield better correct choice performance than to shorter panels. Interestingly, pigeons trained with food rewards abutting the long panels did not outperform pigeons trained with food rewards abutting the short panels, although discrimination performance in both groups at the end of training was modest. Reversal training following the initial discrimination training provided the strongest evidence of successful initial learning, and more importantly, that there was no difference in learning performance between the two groups. The difference in the performance of pigeons compared to previous studies in rats is most easily explained by the different experimental procedures employed, most notably the use of appetitive (pigeons-food reward) compared to aversive (rats-escape in a water maze) motivation. Alternatively, the data support the hypothesis that in similar training environments pigeons, compared to rats, are more likely to combine panels of different lengths into a more holistic geometric representation of space.

Black-capped chickadees categorize songs based on features that vary geographically

The songs of many songbird species vary geographically, yet, the songs of black-capped chickadees, Poecile atricapillus, show remarkable consistency across most of the species' North American range. Previous research has described subtle variations in the song of this species by comparing songs produced by males at distant parts of the species' range (British Columbia and Ontario). In the current study, we used an operant discrimination task to examine whether birds classify the songs produced by males in these two previously studied locations as belonging to distinct open-ended categories. In both experiments, when birds were presented with new songs, they continued to respond to songs from the same geographical location as the songs that were reinforced during initial discrimination training, suggesting that birds were using open-ended categorization. We also presented birds with songs in which we manipulated acoustic features in order to examine the acoustic mechanisms used during discrimination; results provide support that birds use the duration of the song when discriminating, but the results also suggest that birds used additional acoustic features. Taken together, these experiments show that black-capped chickadees classify songs into open-ended, geography-based categories, and provide compelling evidence that perceptible acoustic differences exist in a vocalization that is seemingly consistent across the species' range.

A Simpler Route to Stimulus Equivalence? A Replication and Further Exploration of a “Simple Discrimination Training Procedure” (Canovas, Debert and Pilgrim 2014)

In a recent paper in this journal, Canovas, Debert and Pilgrim (The Psychological Record, 65(2), 337–346, 2015), in their second experiment, taught participants to make one key press to each of three simple visual stimuli and an alternative response to another three. They then trained two new key presses to one stimulus from each class, which then transferred to the other stimuli in each class. When subsequently presented with compounds of two stimuli, participants indicated “correct” to within-class compounds, but “incorrect” to between-class compounds. The present study starts with a successful replication of this seemingly new way of establishing stimulus equivalence classes, with an added matching-to-sample test at the end. In two further experiments, the visual stimuli were replaced by non-words, with two further non-words to be said aloud in place of key-presses. These showed that it was possible to establish two or three equivalence classes using such initial discrimination training, even when the prior demonstration of functional equivalence classes by transfer-of-training to a second set of responses was omitted. Other ways of conceptualizing these methods of training are considered, together with some implications for enlarging our understanding of equivalence class formation.

The easy-to-hard effect in a voluntary exposure to toxin paradigm with rats

In Experiment 1, one group of rats (Group Easy) received initial discrimination training consisting of alternate presentations of two flavor stimuli easily discriminable (presentations of a compound consisting of 0.15% saccharin and 0.15M lithium chloride, LiCl, and presentations of the saccharin alone). In a subsequent phase, these rats learned a hard version of the discrimination (in which the concentration of the saccharin solution was increased to 1.2%) faster than another group of rats (Group Hard) that received continuous training with the hard discrimination throughout all of the experiment. Experiment 2 led us to discard a possible interpretation of these results in terms of differences in the rates with which the neophobic reaction to the saccharin was habituated in the two groups. This study constitutes the first demonstration of an easy-hard effect in a free-intake toxin paradigm.

Temporal sensitivity changes with extended training in a bisection task in a transgenic rat model

The present study investigated temporal perception in a Huntington disease transgenic rat model using a temporal bisection procedure. After initial discrimination training in which animals learned to press one lever after a 2-s tone duration, and the other lever after a 8-s tone duration for food reward, the bisection procedure was implemented in which intermediate durations with no available reinforcement were interspersed with trials with the anchor durations. Bisection tests were repeated in a longitudinal design from 4 to 8 months of age. The results showed that response latencies evolved from a monotonic step-function to an inverted U-shaped function with repeated testing, a precursor of non-responding on trials with intermediate durations. We inferred that temporal sensitivity and incentive motivation combined to control the transformation of the bisection task from a two-choice task at the outset of testing to a three-choice task with repeated testing. Changes in the structure of the task and/or continued training were accompanied by improvement in temporal sensitivity. In sum, the present data highlight the possible joint roles of temporal and non-temporal factors in the temporal bisection task, and suggested that non-temporal factors may compensate for deficits in temporal processing.

A emergência de relações condicionais entre estímulos como resultado de treino de série de discriminações simples simultâneas

O procedimento de emparelhamento de acordo com o modelo tem sido privilegiado para o estabelecimento de discriminações condicionais entre estímulos e para testar a emergência de classes de estímulos equivalentes. No entanto, outros procedimentos de treino discriminativo também têm sido efetivos para o estabelecimento destas classes. Este trabalho teve por objetivo estudar um procedimento de discriminação simples que, com base em discriminações simples já existentes, promoveria a emergência de relações condicionais entre estímulos. Participaram do estudo seis crianças (de seis e sete anos de idade) que trabalharam em computador. Depois de estabelecida uma discriminação simples entre dois estímulos, estes foram sobrepostos a novos estímulos, até a formação de nova discriminação. O mesmo procedimento foi repetido com outros estímulos. Depois de treino discriminativo no qual um participante apresentou apenas seis erros e os demais apresentaram três ou menos erros, testou-se a emergência de relações entre estímulos. Os testes revelaram que houve formação de classes de estímulos equivalentes para três participantes e sugeriram esta possibilidade para outros dois.

Dissociable Roles for the Nucleus Accumbens Core and Shell in Regulating Set Shifting

The ability to behave in a flexible manner is an executive function mediated in part by different regions of the prefrontal cortex. The present study investigated the role of two major efferents of the prefrontal cortex, the nucleus accumbens (NAc) core and shell, in behavioral flexibility using a maze-based strategy set-shifting task. During initial discrimination training, rats learned to use either an egocentric response or a visual-cue discrimination strategy to obtain food reward. During the set shift, animals had to shift from the previously acquired response or visual-cue-based strategy and learn the alternate discrimination. Inactivation of the NAc core, induced by infusion of the GABA agonists baclofen and muscimol, did not impair initial acquisition of either a response or visual-cue discrimination but severely disrupted shifting from one strategy to another. Analysis of the type of errors revealed that impairments in set shifting were not attributable to increased perseveration but to a disruption of the acquisition and maintenance of a new strategy. In contrast, inactivation of the NAc shell did not impair acquisition of either a response or a visual-cue discrimination, or shifting from one strategy to another. However, inactivation of the NAc shell before initial discrimination training improved performance during the set shift relative to control animals. These data indicate that the NAc core and shell make dissociable contributions to behavioral flexibility during set shifting. The NAc core facilitates the acquisition and maintenance of novel behavioral strategies and elimination of inappropriate response options, whereas the shell may mediate learning about irrelevant stimuli.

Visual discrimination learning in zebrafish (Danio rerio)

Three experiments demonstrated visual discrimination learning in zebrafish (Danio rerio). In each experiment, zebrafish were given a choice between two visually distinct arms of a T-maze. Choice of one stimulus was always followed by a food reward, but choice of the other stimulus was not rewarded. Different colored sleeves fitted around the arms of the T-maze were used in Experiments 1 (green and purple) and 2 (red and blue). The stimuli used in Experiment 3 were white sleeves lined with horizontal or vertical black stripes. In all three experiments, zebrafish acquired a significant preference for the stimulus that led to a food reward. Experiments 1 and 2 also showed that zebrafish could learn a reversal of the discrimination. Finally, the effect of discontinuing food rewards was examined after reversal training in Experiment 2 and after initial discrimination training in Experiments 1 and 3. Non-reinforcement led to a decrease in correct responding in Experiments 2 and 3 independent of stimulus identity, but to an asymmetrical pattern of responding in Experiment 1. The median latency to make a choice response decreased over the course of acquisition in all three experiments; during extinction, median response times did not change at all in Experiment 1 and increased only very slightly in Experiment 2, but showed a substantial increase in Experiment 3. The implications of these results for the zebrafish as a model system for genetic studies of learning and memory are discussed.

Reinforcer Rate and Stimulus Control in Discrimination Reversal Learning

Nine subjects with mental retardation were trained with a fading procedure to perform two-choice simple-discrimination tasks. Immediately after meeting a learning criterion, discrimination reversals were trained within the same sessions, also with the fading procedure. Two 10- or 16-reversal conditions were compared within subjects: High, in which all correct responses for the initial discrimination were followed by reinforcers, and Low, in which the initial discrimination was trained with an intermittent reinforcement schedule and a lower obtained reinforcer rate. In both conditions, reinforcers followed all correct responses during reversal training. Reversal learning error rates were higher in the High condition for 8 subjects. Thus, the rate of reinforcement during the initial discrimination training was related to the persistence of stimulus control, as shown by more selections of the initially positive stimulus during reversal training in the High condition. The results are consistent with behavioral momentum theory. The results indicate that (a) behavioral momentum may describe stimulus control in discrete-trial procedures, and (b) teaching procedures may sometimes benefit from tactical reductions in local reinforcement density to encourage changes or transfers of stimulus control.

Whole Reversal Versus Partial Reversal Advantage Effect on Same-Different Discriminations in Rats

The present experiment has examined a whole reversal versus partial reversal advantage effect on same-different discrimination using a whole-partial reversal procedure in rats. This experiment was a limited parameter study of the reinforcer density variable from Phase 1 training to Phase 2 reversal. Rats were trained to criterion on 12 same-different tasks (6 same and 6 different tasks) and then given reversal training on either a whole reversal condition (W), in which all of the 12 tasks were reversed, a partial reversal-10-condition (P-10), in which 5 same and 5 different tasks were reversed, a partial reversal-6-condition (P-6), in which 3 same and 3 different tasks were reversed, or a partial reversal-2-condition (P-2), in which one same and one different task were reversed. Group W reversed faster than the other three partial groups. Group P-2 reversed faster than Group P-6, which in turn reversed faster than Group P-10. These results provided evidence that rats formed functional stimulus classes during initial same-different discrimination training.

Emergence of Conditional Stimulus Relations and Transfer of Respondent Eliciting Functions Among Compound Stimuli

Previous research has demonstrated that conditioned elicitation functions can transfer via stimulus equivalence classes. However, thus far investigations in this area have been limited to stimulus equivalence classes involving single element stimuli. This study attempted to demonstrate the transfer of eliciting functions via emergent relations involving compound stimuli. Eight college students participated in this study. Six of these participated in all experimental procedures, while the remaining two served as controls and did not receive some phases of the experiment. The experimental participants were first taught nine conditional relations of compound stimuli and unitary stimuli (AC-B & BC-A) using match-to-sample training. They were then tested for the emergence of untrained relations involving different combinations of the previously learne9 compound-single element relations and compound-compound relations (AC-AC or AB-AB or BC-BC). A classical conditioning procedure was then performed in which one compound stimulus from one class was paired with mild electric shock (1.0-2.0 mA) while two other compounds from two different classes were presented in the absence of shock. Participants were then presented with other compounds from the appropriate classes to assess whether the eliciting function had transferred to stimuli which were members of the same class as the originally conditioned stimulus. The control participants received the same procedures except for the initial conditional discrimination training of the compound-single relations and the testing for the emergence of compound-single relations. Four of thoe six experimental participants demonstrated transfer of the eliciting function. An analysis of the performance of both of the individuals who failed to demonstrate the transfer revealed that they may have failed to ° maintain the classes throughout the experiment. One participant discontinued the experiment before further procedures

Behavioral skills training to remediate deviant social behavior of an adolescent in residential treatment

This case conference paper describes a treatment plan for Mike, an intellectually limited 13-year-old boy with social-skill deficits and social behavior problems who resides in a family-style residential treatment program. Treatment would involve initial training with videotape vignettes for Mike to learn to identify appropriate and inappropriate social behaviors across a variety of typical social situations with peers. Following initial discrimination training, behavioral skills training procedures involving instructions, modeling, rehearsal, praise, and feedback would be implemented with peers in simulated social interactions. Training would include multiple exemplars and would continue until Mike had learned appropriate social behaviors for a wide range of social situations and had exhibited those behaviors in the residential and school settings. Behavioral contingencies would also be implemented by staff for Mike's appropriate and inappropriate social behaviors in the residential and school settings to promote generalization.

Cross-modal transfer as a function of similarities between training tasks in classical conditioning of the rabbit

The present experiments examined transfer of training from visual to auditory sensory modalities in classical conditioning of the rabbit’s nictitating membrane response. Experiment 1 examined transfer from initial training with a single visual CS to subsequent auditory discrimination training, and Experiment 2 examined transfer from visual discrimination training to auditory discrimination training. The major findings were that (1) initial conditioning of a visual CS facilitated the overall rate of CR acquisition to the auditory CSs separate from the requirements for discrimination learning (Experiments 1 and 2), and (2) initial visual discrimination training facilitated auditory discrimination learning (Experiment 2). Thus, the animals appeared to encode separately both contiguous CS-US relations and CS+ versus CS− relations during initial visual training. The results are discussed with respect to theories of extradimensional transfer.

Noncontingent and contingent no-choice intervals and concurrent performance

Pigeons responded to changeover-key concurrent variable-interval variable-interval reinforcement schedules while there were intervals during which the changeover key was inoperative (no-choice intervals). In Experiment 1, a multiple schedule on the changeover key signaled choice and no-choice intervals. All subjects showed near-perfect discrimination during initial discrimination training and rapid reacquisition of discrimination following contingency reversals. In Experiment 2, the onset of no-choice intervals was unsignaled and contingent on interchangeover time. The temporal distribution of changeover-key responses conformed to the temporal distribution of choice intervals. The results of both experiments suggest that changeover responding is modifiable as a function of its immediate consequences. The results of Experiment 2, in particular, suggest that time or some correlate of time since the last changeover response can determine subsequent changeover behavior.

Discrimination of the number of sequential events by rats

Ten rats were trained to press a right lever following two successive sounds and to press a left lever following four successive sounds. Three sound sequences were used in initial discrimination training, such that reliable classification could not be based on the duration of each sound, the interval between sounds, or the total duration of the sound sequence. Classification of seven novel sound sequences suggested that the animals were either using number or the sum of sound durations in a sequence as the relevant cue. When this total sound duration was put in conflict with number, rats classified by number. The conclusion was that rats can discriminate number, even when temporal cues are controlled.

Short-term retention of "surprising" events by pigeons.

Terry and Wagner (1975) have suggested that the short-term retention of information about an event is enhanced if the occurrence of the event is made unexpected or surprising. Three experiments tested this idea using delayed conditional position (Experiment I) and colour discriminations (Experiments II and III). The subjects were pigeons and the presentation of food was the target event to be remembered. Choice of one of two simultaneously presented stimuli was reinforced if the retention interval had been initiated by presentation of target food. Contrary to Terry and Wagner's claim, retention was superior on probe test trials in Experiments I and II if the presentation of the target food was preceded by a previously established signal for food (CS+) rather than by a stimulus which had not been paired with food (CS-). Experiment III systematically manipulated the signalling conditions used during initial discrimination training. Retention was better following a CS+ presentation if the target food had been signalled during initial discrimination training but worse if the food presentation had been unsignalled. These results do not favour the idea that retention of an event is directly affected by whether or not the target event is surprising.

Figure-background color differences and transfer of discrimination from objects to line drawings with pigeons

The effect of varying the color of the background behind two solid object discriminanda on transfer to line drawings was tested with pigeons. In Experiment 1, objects were placed in front of either a white or gray background for initial discrimination training, then, in transfer tests in extinction, the display background colors were either the same or switched, or the display was a line drawing of the objects. The switch from gray to white disrupted performance about as much as the switch to the line drawing. The switch from white to gray did not disrupt performance as much, but, again, no transfer to the line drawing was seen. In Experiment 2, the background color behind the objects was changed every day, the intention being to make background color irrelevant. No transfer to line drawings following this training was seen.

Overtraining and extradimensional shift learning by cats

Twenty-four cats were trained with stimuli that presented uncorrelated differences in size and brightness, on discrimination and extradimensional shift (EDS) problems in a Grice box. The cue relevant in EDS training was present and irrelevant in initial discrimination training, and the cue relevant in discrimination training was present and irrelevant in EDS training. Cats overtrained for 144 trials in discrimination training learned the EDS as quickly as animals switched to EDS without overtraining. This result is hard to reconcile with Sutherland and Mackintosh’ s attention theory of discrimination learning by animals.