Effects of stimulus differentiation training upon hypotheses,strategies, and stereotypes in discrimination learning among kindergarten children

Two groups of kindergarten children received stimulus differentiation training either with feedback (experimental Ss) or without (controls), prior to presentation of a series of discrimination-learning problems using blanktrial probes. Results were as follows: Performance of both groups was virtually perfect during differentiation training (less than one error per 1000 trials). In transfer, however, experimental Ss solved more problems, generated more consistent Ss during blank-trial probes, manifested fewer response sets, were more likely to abandon a disconfirmed H, sampled more locally consistent Ss following errors, and retained a confirmed H more frequently than control Ss. Experimental Ss also manifested strategy Sys (hypothesis sampling systems) predominately, while controls generated only stereotypes. Findings were discussed in relation to theoretical perspectives derived from Piagetian theory and developmental learning theory.     

Encoding-imagery specificity in alcohol state-dependent learning.

A free-recall procedure demonstrated state-dependent learning using alcohol. Tests of long-term memory showed that both high- and low-imagery words were less likely to be recalled if stored while intoxicated rather than under sober conditions. However, information encoded and stored while intoxicated was more effectively retrieved when later tests of recall were performed while intoxicated, as compared to recall accomplished in the sober state. This dissociative recall effect was far more robust with low-imagery than with high-imagery words.     

Extinction-induced neuroplasticity attenuates stress-induced cocaine seeking: a state-dependent learning hypothesis

Chronic drug use weakens excitatory neocortical input to the nucleus accumbens (NAc). We previously reported that extinction training, a form of inhibitory learning that progressively reduces cocaine-seeking behaviour when reward is withheld, reverses this deficit by up-regulating GluR1 and GluR2/3 subunits of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) glutamate receptors in the NAc. The level of GluR1 up-regulation is positively associated with a reduction in cocaine seeking, suggesting that extinction-induced up-regulation in AMPA receptors in the NAc opposes motivational influences that maintain cocaine seeking. This hypothesis is supported by the finding that over-expression of GluR1 and GluR2 in the NAc facilitates extinction of cocaine self-administration. Furthermore, a single extinction training session conducted during GluR1 and GluR2 over-expression strongly and selectively attenuates the ability of an environmental stressor to trigger relapse to cocaine seeking long after GluR1 and GluR2 over-expression declines. These results could suggest that excitatory input to the NAc promotes extinction learning, but only when memory is recalled under stressful situations. Recent studies indicate that both environmental stress and the frustrative stress of withholding reward during extinction of drug self-administration induce similar neurochemical events in the NAc. These neurochemical events could impose a "state-dependency" on extinction learning such that subsequent exposure to stress acts as a cue to enhance retrieval of extinction memory. Our results suggest that extinction-induced up-regulation in NAc AMPA receptors acts reciprocally to facilitate state-dependent extinction learning, as stressful situations evoke extinction memories that exert powerful inhibitory control over drug-seeking behaviour. These results may have important therapeutic implications for behaviour-based approaches aimed at treating drug addiction.     

Serial learning in rats: A test of three hypotheses

Findings obtained by providing rats with a single fixed series of events, A-B-C-…, often are equally compatible with three alternative serial learning interpretations: that the signal for items is (A) their position in the series (position view), (B) the prior item of the series (chaining view), and (C) one, two, or more prior items of the series (sequential view). By employing a novel procedure of supplying rats with two different series, rather than a single series, it was possible to choose between the three alternatives. Employing 10 and 0, 0.045 g, Noyes pellets as items, rats in both runway experiments reported here received a three trial series, either a 10-0-10 series or a 0-0-10 series. In Experiment 1, the other series was a single 0 pellet trial (along with 10-0-10) or a single 10 pellet trial (along with 0-0-10). In Experiment 2, the other series was either 0-0 (along with 10-0-10) or 10-0 (along with 0-0-10). Considering both experiments, findings were consistent with the sequential view but not with either the position view or the chaining view. The possibility was suggested that, under some other experimental conditions, particularly those not employing reward events as items, greater control over discriminative responding might be exercised by position cues than by item cues.     

Disagreement and causal learning: Others' hypotheses affect children's evaluations of evidence

When children evaluate evidence and make causal inferences, they are sensitive to the social context in which data are generated. This study investigated whether children learn more from evidence generated by an agent who agrees with them or from one who disagrees with them. Children in two age groups (5- and 6-year-olds and 9- and 10-year-olds) observed the functioning of a machine that lit up and played music in the presence of certain objects. After endorsing one of two plausible causal hypotheses, children observed a puppet either agree or disagree with their own hypotheses. The puppet then generated a further piece of evidence that confirmed, disconfirmed, or was neutral with respect to the children's hypotheses. When they were later asked to make causal inferences about objects they did not directly observe, children in both age groups responded differentially to identical evidence depending on whether the agent agreed or disagreed, and they often drew stronger inferences in response to disagreement. In addition, older children were particularly sensitive to disagreement when the evidence was ambiguous. Our results suggest that children consider the relationship between their own and others' hypotheses when evaluating evidence that others generate. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Amnesic effects of diazepam: "Drug dependence" explained by state-dependent learning

An experimental study on 12 healthy volunteers showed that an amnesic effect of a therapeutic dose of diazepam (10 mg 3 times a day) may be explained by a theory of state-dependent learning. Asymmetric state-dependence was demonstrated by visually as well as verbally learned material, but in the latter case there was also evidence of an anticonsolidating effect upon learning. The findings are related to drug dependence, and it is suggested that therapeutic gains obtained during long-term diazepam treatment may not transfer to the no-drug state.     

Comparisons of stimulus learning and response learning in a punishment situation

These experiments use a procedure in which a rat is trained to make two topographically distinct responses on a single manipulandum, and then one of the responses is punished. Differential suppression of the punished response is taken as evidence of response learning, whereas the common suppression of both responses is attributed to stimulus learning or to general and nonassociative factors. Thus, this procedure begins the experimental separation of animals learning about the consequences of their behavior and animals learning what happens in a particular environment. A further separation is effected by using two such manipulanda; this procedure begins to distinguish between stimulus learning about the manipulandum and the more gereral factors that cause suppression. Some parameters affecting the relative importance of stimulus learning and response learning are examined.     

Discrimination learning during the first year: stimulus and positional cues

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

Note on subjects' hypotheses in multiple-cue probability learning

Subjects' hypotheses in multiple-cue probability learning was studied by trial-by-trial verbal reports in tasks with linear and nonlinear cue-criterion relations. In accordance with earlier findings, the results of the present experiment show that subjects learned linear tasks rapidly, while nonlinear tasks were not learned at all. The subjects' verbal hypotheses show that the subjects were concerned with rules for combining cue values, rather than with cue-criterion functions. This explains why the subjects fail to learn nonlinear multiple-cue tasks. It also shows that, although the subjects seem to learn multiple-cue tasks through a hypothesis testing process of the same kind as in single-cue probability tasks, the hypotheses tested in multiple-cue tasks are different from those tested in single-cue tasks. Finally, the present results suggest that the picture of the subjects' cognitive models of multiple-cue probability learning tasks provided by the customary multiple regression analysis may be fundamentally misleading in that it suggests that the subjects learn the validity of each cue rather than a combination rule.     

Verbal reports of stimulus effects on learning: Introspection revisited

The accuracy of subjects' verbal reports on the respective causal roles of relevant and irrelevant stimulus factors on learning was investigated. In two experiments, university undergraduates learned strings of letters that were either grammatically structured or unstructured (a causal variable) and either color coded or black (a salient but irrelevant variable). Results indicated that subjects reported more causal impact of color than structure on the learnability of lists, despite the fact that the latter variable and not color had an actual effect on learning. It was proposed that verbal reports of stimulus effects on one's own behavior can be regarded as a task in estimates of covariation rather than direct retrieval of memory traces.     

Observation and discrimination learning in the rat: Effects of stimulus substitution

Effects of prior observation of modeling performances upon learning simultaneous visual discriminations were studied in nine groups of rats. Stimulus patterns which had been positive (“Cued”) or negative (“Uncued”) for the model animal and novel stimuli were presented. Observers learned faster if discriminations required approach to, rather than avoidance of, the previously positive stimulus. Approach to the negative stimulus was acquired more rapidly only if the second stimulus was novel. Approaches to a substituted new stimulus combined with either of the previously viewed stimulus patterns required nearly twice the training needed for a similar response attachment when both stimuli were novel. Attentional changes appear to underlie the stimulus control exerted over the observer rat in instrumental learning situations.