Positive and negative patterning after CS preexposure in flavor aversion conditioning

Three experiments examined rats’ ability to discriminate a compound conditioned stimulus (CS) from the individual elements of that compound in a flavor aversion conditioning paradigm. In Experiment 1, presentations of a compound of sucrose and saline solutions were followed by lithium chloride injections, but presentations of those elements individually were nonrein-forced (positive patterning). Conversely, in Experiments 2 and 3, presentations of the individual elements were followed by lithium chloride injection, but compound presentations were non-reinforced (negative patterning). The discriminations were acquired in all three experiments. In addition, all three experiments investigated the effects of preexposure of the discriminative stimuli on subsequent acquisition of the patterned discriminations. In positive patterning, preexposure had no measurable effect on the acquisition of responding (suppression) to the reinforced compound stimulus, but slowed the loss of suppression to the nonreinforced elements. In negative patterning, preexposure slowed the acquisition of suppression to the reinforced elements but had little effect on the loss of suppression to the nonreinforced compound.     

Effect of outcome valence on positive and negative patterning in human causal reasoning

The importance of configural cues and whether a situation involves beneficent or maleficent outcomes was investigated in two experiments on human causal reasoning, based on experienced causal information. Participants learned positive and negative patterning discriminations involving either beneficent or maleficent outcomes in a health-reasoning task and in a social-reasoning task. With maleficent outcomes, positive patterning was consistently easier to learn than negative patterning, a positive patterning advantage that is predicted by current associative theories and commonly taken as evidence for configural cues. However, with beneficent outcomes, the two discrimination tasks were not significantly different in ease of learning, a result not predicted by current theories. The reliable positive patterning effect found with maleficent outcomes broadens the range of conditions in which the effect can be shown in causal reasoning. The novel effect of outcome valence poses an interesting theoretical challenge for attempts to account for the relation between learning about individual cues and combinations of those cues.     

Resistance to interference in complex negative patterning

Resistance to interference was examined in rats that received a complex negative patterning discrimination in which XA and XB were followed by food reinforcement and XAB was not. Retention of the discrimination was evident after separate reinforcement of both A and B (Experiment 3), but not after reinforcement of either AB (Experiments 1 and 3) or XAB (Experiments 2 and 3). These data suggest that complex negative patterning discriminations are acquired configurally and that the relative similarity of the original discrimination and subsequent interference trials dictates the final degree of retention observed.     

Representations of single and compound stimuli in negative and positive patterning

In four experiments, rats were trained on different patterning discriminations before being tested with compounds composed of novel combinations of the trained stimuli. In Experiment 1, rats were trained on a negative-patterning schedule (A+ B+ AB-) intermixed with reinforced presentations of a second compound (CD+). On a subsequent test, the rats responded more to two novel compounds, AC and BD, than to A and B, but less than to CD. In Experiment 2, rats were trained on two concurrent negative-patterning discriminations (A+ B+ AB-, C+ D+ CD-). On test, they responded more to AC and BD than to AB and CD, but less than to the single stimuli. In Experiment 3, rats were trained on two concurrent positive-patterning discriminations (A-B- AB+, C- D- CD+). On test, their response rates to AC and BD were not different from the response rates to the trained compounds (AB and CD). Finally, in Experiment 4, rats were trained on a positive- and negative-patterning discrimination concurrently. Once again, on test, response rates to AC and BD were not different from responding on reinforced trials of the trained discriminations (A+, B+, and CD+). We discuss the implications of these findings for elemental and configural models of stimulus representation.     

Temporal discrimination using different feature-target intervals in classical conditioning of the rabbit’s nictitating membrane response

In a typical conditional discrimination, a target stimulus (X) is reinforced during one feature cue (A→X+), but not during another feature cue (B→X−). The present experiments used only a single “feature” cue (a 66-sec tone). On half of the trials, the target stimulus (a 400-msec light) was paired with the reinforcer when the feature-target interval was one duration (e.g., 5 sec). On the remaining trials, the interval was different (e.g., 45 sec), and the target stimulus was presented without the reinforcer. All the animals acquired this temporal discrimination, and subsequent testing with other feature-target intervals yielded generalization-like gradients. These results provide solid evidence that each portion of a feature cue is encoded in a distinctive fashion. Had temporal encoding not occurred, the feature cue would have been just as ambiguous a predictor of the reinforcer as was the target stimulus, and discrimination would not have been possible. The integration of real-time temporal encoding mechanisms into models of conditional discrimination is discussed.     

Generalization of fixed-interval response patterning in pigeons

Three pigeons were trained on a multiple schedule in which keypecking was reinforced on a fixed-interval (FI) schedule in the presence of a vertical line and on a variable-interval (VI) schedule in the presence of a horizontal line. Response rates in the former component were positively accelerated (the “FI scallop”), whereas response rates in the second component were relatively constant. In a subsequent generalization test on the line-tilt continuum, the index of curvature decreased systematically as the line was rotated from vertical to horizontal in 30-deg steps. Frequency distributions of indices of curvature suggested that intermediate average index values for intermediate generalization test stimuli were mainly the result of intermediate response patterns in the individual test stimulus presentation, rather than the averaging of VI-like patterns during some stimulus presentations with FI-like patterns during other stimulus presentations.     

Biological constraints on instrumental and classical conditioning: Retrospect and prospect

The adequacy of traditional approaches to the study of animal learning to account fully for learning phenomena has been seriously questioned during the past decade. Critics of traditional analyses advocated a biological orientation to the interpretation of associative processes and introduced a variety of concepts intended to provide a new framework for the study of animal learning. This promise of a reorientation of the field has not been realized. The concepts of biological constraints, adaptive specializations, and situation specificity of learning have had a less profound influence on the general process approach to instrumental and classical conditioning than anticipated. The present paper makes explicit the conceptual bases of the original biological approaches to learning, identifies reasons why they failed to change fundamentally the study of instrumental and classical conditioning, and proposes an alternative approach to the use of ecological and evolutionary principles in studies of conditioning. We suggest a renewed comparative approach to the study of learning phenomena that avoids many of the difficulties inherent in earlier formulations by providing (1) a strategy for the discovery of adaptive specializations in learning, (2) an ecological framework for the discussion of these adaptive specializations, and (3) a renewed emphasis on the study of species differences in learning.     

Motivational vs. associative role of the US in classical conditioning of the rabbit’s nictitating membrane response

Two experiments tested the motivational role of the US in classical conditioning of the rabbit’s nictitating membrane (NM) response. In Experiment 1, subjects were trained to an intermediate performance level and then given a series of (1) CS-US trials, (2) “backwards” US-CS trials, (3) CS-alone trials, (4) US-alone trials, or (5) no-stimulus presentations. Interpolated presentations of the US, either alone or in a backwards contingency, tended to produce an impairment of subsequent acquisition. In Experiment 2, subjects were trained with strong or weak US intensity on paired or interpolated trials. US intensity on interpolated trials had only a very small effect, whereas the effect of US intensity on paired trials was quite large. Shifts in paired-trial US intensity produced corresponding shifts in performance, but shifts in the intensity of the interpolated US produced no apparent effect. We conclude that the arousal of motivation is not sufficient to maintain performance in classical NM conditioning.     

The effect of US omission in classical aversive and appetitive conditioning of rabbits

Rabbits (Oryctolagus cuniculus) were given either a 100% or a 50% reinforcement schedule in classical conditioning. Two groups received an aversive US (shock) and two groups received an appetitive US (water to the oral cavity). With parameter estimates for the two-phase model serving as the dependent variables, it was possible to define more precisely the effect of US omission with the intermittent reinforcement schedule. For the aversive preparation, the major effect of intermittent reinforcement was to increase the duration of Phase 1, a phase during which response likelihood remains constant at its initial value. Only a small proportion of subjects reflected the effect of US omission during Phase 2, the “learning” phase, this being a low operator limit following trials on which neither the CR nor the US occurred. The major effect of US omission for the appetitive preparation was in Phase 2, primarily a result of a minority of subjects having a low operator limit following trials on which neither the CR nor the US occurred. Many subjects required separate operators for trials on which the CR did or did not occur. The results were interpreted to pose difficulties for strength theories of conditioning, and the limitation implied for successful application of the Rescorla-Wagner theory are discussed. The implications of the data for response-contingent interpretations and for individual differences are also discussed.     

Transfer across CS-US intervals and sensory modalities in classical conditioning of the rabbit

Two experiments investigated transfer of the rabbit’s conditioned nictitating membrane response (NMR) from shorter to longer CS-US intervals in conjunction with a change in CS modality, for example, light to tone. In Experiment 1, three experimental groups received initial training with a 400-msec CS-US interval, which produced substantial CR acquisition, and three control groups received initial training with a 2,800-msec CS-US interval, which produced minimal CR acquisition. Subsequently, the experimental and control groups received training with an 800-, 1,800-, or 2,800-msec CS-US trace interval. At the same time, the modality of the CS was changed from tone to light (or vice versa). Experiment 2 contained three groups that received initial exposure to a 400-msec CS-US interval, a 2,800-msec CS-US interval, or just the experimental chambers. Subsequently, all three groups received training with an 800-msec CS-US interval in a different CS modality. The results of both experiments revealed substantial positive transfer across CS modalities from the 400-msec CS-US interval to the 800-msec CS-US interval. There was also significant transfer to the 1,800-msec but not the 2,800-msec CS-US interval. The transfer did not appear immediately on test presentations of the second CS. Rather, the transfer appeared as an enhancement in the rate of CR acquisition after reinforced training with the second CS had commenced. The results are discussed with respect to mechanisms of transfer and facilitation of trace conditioning.     

Summation and configuration between and within sensory modalities in classical conditioning of the rabbit

Three experiments examined “atomistic” and “configurai” processes in stimulus compounding using the rabbit’s conditioned nictitating membrane response. Two conditioned stimuli (CSs) were trained separately and then tested together in a compound. Animals trained with CSs from different modalities—namely, tone and light—showed summation in both acquisition and extinction. That is, the probability of a response to the compound could be predicted by the statistical sum of responding to the CSs. In contrast, animals trained with CSs from the auditory modality, tone and noise, showed a level of responding to the tone + noise compound that was the same as that of the CSs, well under the level predicted by the statistical sum of responding to the CSs. In conclusion, atomistic processes appear to predominate in cross-modal compounding. Configurai processes may occur during compounding within the auditory modality, but atomistic alternatives—namely, common elements and selective attention hypotheses—may be able to explain the results.     

Positive and negative experiences related to doctoral study conditions

ABSTRACT

During their doctoral studies, students undergo an emotionally and intellectually intensive process involving a wide range of positive and negative experiences. This article analyses PhD students’ perceptions of the most positive and negative experiences related to doctoral study conditions. Previous researchers have primarily focused on analysing experiences that negatively affect doctoral work and have related these experiences to institutional, social and individual variables. However, little is known regarding positive experiences and how both positive and negative experiences are interpreted and related to variables connected with doctoral study, such as discipline, funding, enrolment type, and the stage of the doctoral process. In total, 1173 doctoral students from 56 Spanish universities completed an open-ended online survey. The findings indicate that opportunities for PhD students to communicate their scientific advances, receive expert feedback and interact with other researchers have a high positive influence on their doctoral journey. However, funding difficulties, particularly for students in the social sciences, and relationships with the research community, principally with the supervisor, were perceived as the main negative challenges. Experiences related to research design, data collection and analysis were perceived either negatively – primarily for mid-level students – or positively. These results should be considered in future doctoral programme policies to determine when, how and why to provide specific support during the doctoral process.     

Savings in classical conditioning in the rabbit as a function of extended extinction

In the present experiments, savings phenomena following a limited amount of initial acquisition and extended extinction were examined. Experiments 1 and 2 compared rates of reacquisition following brief acquisition and various amounts of extinction in conditioning of the rabbit’s nictitating membrane and heart rate response, respectively. Experiment 3 compared rates of acquisition to a novel stimulus (e.g., light) following brief acquisition and various amounts of extinction to another stimulus (e.g., tone). In addition, in Experiment 3 recovery of responding to the extinguished stimulus during acquisition to the novel, cross-modal stimulus was examined. Experiments 1, 2, and 3 demonstrated that with a limited number of acquisition trials (1) there was a graded reduction in the rate of reacquisition as a function of the number of extinction trials in both conditioning preparations, (2) there was a graded reduction in the rate of cross-modal acquisition as a function of the number of extinction trials, but (3), in Experiment 3, recovery of responding to the extinguished stimulus during cross-modal training of the novel stimulus appeared uniformly robust even in the face of extended extinction.     

图式理论在英语阅读理解中的作用与缺失

图式理论在英语阅读理解中具有促进作用。语言图武、内容图式和形式图武对英语阅读理解的促进作用,发现图武知识在提高读者阅读能力的同时,其本身的特点及其工作机制还会对英语阅读理解产生障碍,该理论在阅读理解中也存在不足之处。图式干扰、合适图武的选择问题以及图式作用的非决定性,构成了图式理论的主要不足因素。     

图式理论在英语阅读理解中的作用与缺失

图式理论在英语阅读理解中具有促进作用。语言图式、内容图式和形式图式对英语阅读理解的促进作用，发现图式知识在提高读者阅读能力的同时，其本身的特点及其工作机制还会对英语阅读理解产生障碍，该理论在阅读理解中也存在不足之处。图式干扰、合适图式的选择问题以及图式作用的非决定性，构成了图式理论的主要不足因素。     

Solving Pavlov's puzzle: Attentional, associative, and flexible configural mechanisms in classical conditioning

This article introduces a new "real-time" model of classical conditioning that combines attentional, associative, and "flexible" configural mechanisms. In the model, attention to both conditioned (CS) and configural (CN) stimuli are modulated by the novelty detected in the environment. Novelty increases with the unpredicted presence or absence of any CS, unconditioned stimulus (US), or context. Attention regulates the magnitude of the associations CSs and CNs form with other CSs and the US. We incorporate a flexible configural mechanism in which attention to the CN stimuli increases only after the model has unsuccessfully attempted learn input-output combinations with CS-US associations. That is, CSs become associated with the US and other CSs on fewer trials than they do CNs. Because the CSs activate the CNs through unmodifiable connections, a CS can become directly and indirectly (through the CN) associated with the US or other CSs. In order to simulate timing processes, we simply assume that a CS is formed by a temporal spectrum of short-duration CSs that are activated by the nominal CS trace. The model accurately describes 94?% of the basic properties of classical conditioning, using fixed model parameters and simulation values in all simulations.     

A comparison of the Rescorla-Wagner and Pearce models in a negative patterning and a summation problem

In two experiments, we examined two related conditioning problems previously investigated by Red-head and Pearce (1995a) and Pearce, Aydin, and Redhead (1997). Experiment 1 involved an A+, B+, C+, AB+, AC+, BC+, ABC2 discrimination. The Rescorla-Wagner model predicts that response to AB, AC, and BC will be greater than that to A, B, and C at asymptote, whereas the Pearce model makes the opposite prediction. In Experiment 2, we investigated the responding to a novel ABC compound in groups trained with either A+, B+, C+ or AB+, AC+, BC+. The Rescorla-Wagner model predicts greater response to ABC in the group trained with A+, B+, C+ than in the group trained with AB+, AC+, BC+, whereas the Pearce model makes the opposite prediction. In contrast to the findings of Redhead and Pearce (1995a) and Pearce et al. (1997) in pigeon autoshaping, our findings in rabbit eyelid conditioning support the Rescorla-Wagner model.     

Temporal specificity in patterning of the rabbit nictitating membrane response

Rabbits were trained in either positive patterning (AX+, A−, X−) or negative patterning (A+, X+, AX−) using one of four intervals between the onset of A and the onset of X on AX trials. These intervals were 0, 800, 2,400, and 5,600 msec. In each task, all groups acquired an appropriate pattern of discriminative responding. Following acquisition, all rabbits were tested with the four different A-X intervals. All positive patterning groups showed an excitatory gradient, in which the highest level of responding occurred at the interval used in training. Conversely, all but one of the negative patterning groups showed an inhibitory gradient, in which the lowest level of responding occurred at the interval used in training. The one exception was the negative patterning group trained with simultaneous AX stimuli (0 msec), which showed a low, broad gradient, indicating transfer of inhibition across all the intervals. The results are discussed with respect to temporal encoding mechanisms and accounts of conditional discriminations.