Transfer across unconditioned stimuli in serial feature discrimination training.

The transfer of conditioned modulation across CS and unconditioned stimulus/stimuli (UCS) was examined in 3 experiments that used Pavlovian appetitive training procedures with rats. In Exp 1, after training in a positive patterning discrimination (X→A+/X-/A-), X increased CR elicited by another trained-then-extinguished CS as long as that CS had been trained with the same UCS as was used in discrimination training. In Exp 2, after training with a feature-negative discrimination (X→A-/A+), X inhibited CR elicited by another trained-then-extinguished CS as long as that CS had been trained with the same UCS. Exps 1 and 2 used a between-groups design, and Exp 3 used a within-groups design. In Exp 3, rats were trained in a feature-positive discrimination (X→A+/A-). In transfer tests, X increased CR elicited by another CS trained then extinguished with the same UCS from training. This increase was greater than the X increased CR elicited by another CS trained then extinguished with a different UCS from training. Results supported the suggestion that features trained in serial discrimination tasks influence behavior indirectly by transiently raising or lowering the threshold for activation of the UCS representations by its target stimuli and by any other stimuli that may be associated with that UCS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retention of response persistence in weanling and adolescent rats.

Two experiments (192 Sprague-Dawley rats) examined parameters affecting retention of continuously reinforced (CRF) and partially reinforced (PRF) runway training in weanling and adolescent Ss. In Exp I, weanling Ss were given CRF or PRF training and 12 hrs, 3 days, or 10 days later were given 8 CRF reacquisition trials followed by extinction. In Exp II, weanling and adolescent Ss were given CRF or PRF runway training and extinguished 10 days later following 0, 8, or 24 CRF reacquisition trials. Results suggest that (a) weanlings characteristically display a partial reinforcement extinction effect (PREE) of unusually large magnitude if extinguished within 12 hrs of training, (b) this large-magnitude PREE dissipates within 3 days of training regardless of the number of CRF reacquisition trials preceding extinction, (c) no PREE of any magnitude is seen in weanlings or adolescents following a 10-day interval unless CRF reacquisition trials precede extinction, and (d) retention of the PREE is poor or nonexistent in Ss trained as adolescents and extinguished 10 days later, even with CRF reacquisition preceding extinction. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterned (single) alternation in infant rats after combined or separate lesions of hippocampus and amygdala.

The role of the developing hippocampus and the amygdala on patterned (single) alternation (PA) in the infant rat was investigated in 4 experiments. In Exps 1 and 2, Ss were given 2 bilateral electrolytic hippocampal lesions or sham surgeries at 10 or 11 days of age and were trained 6 days later in a straight runway. In Exp 1, there were 120 trials in 1 day, with an 8-, a 15-, or a 30-s intertrial interval (ITI). PA learning occurred in lesion and sham Ss at the 8- and 15-s ITIs. In Exp 2, training was extended to 240 trials over 2 days, with a 30- or 60-s ITI. Sham and lesion Ss showed PA at the 30-s ITI, but the emergence of PA was delayed in the lesion pups at the 60-s ITI. In Exp 3, amygdaloid lesions had no effect on PA learning at the 8-s ITI. However, when Ss with hippocampal and amygdaloid lesions were trained at the 8-s ITI, the emergence of PA was delayed, and its size was reduced (Exp 4). Results argue for a role of the hippocampus in PA learning at long ITIs and suggest that, even in 16-day-old Ss exposed to an 8-s ITI, the combined hippocampal and amygdaloid lesion produces a deficit greater than either the hippocampal or the amygdaloid lesion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory discrimination, reversal learning, and stimulus control in rats.

Conducted 3 experiments with a total of 21 Wistar rats. In Exp I Ss were trained to discriminate lights, tones, or odors and then given a series of discrimination reversals. Only Ss trained with odors showed positive transfer on the first reversal and acquisition of a reversal set. Other experiments demonstrated that (a) Ss preferentially attended to odors when presented in compound with lights or tones; (b) odors exerted more discriminative control than tones in tests using compound stimuli of competing sign; and (c) after pretraining on the positive stimulus, acquisition of an odor but not a light discrimination occurred with virtually no errors. These results demonstrate the importance of stimulus modality in the establishment of stimulus control and the need for more careful analysis of stimulus factors in cross-species comparisons of learning ability. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of overtraining on reversal and extradimensional shifts in schizophrenics.

In Exp. I, 50 schizophrenic Ss were trained under 1 of 3 discrimination learning conditions: reversal (R) shift, extradimensional (ED) shift, or control. 1/2 of the Ss in each shift condition received overtraining on the preshift discrimination. Performances of nonovertrained Ss on the R and ED shifts were very similar to performances of schizophrenic Ss tested by J. D. Nolan (see 42:11). Newman-Keuls analyses indicate that overtraining facilitated the R shift relative to the ED shift. The result was a significant overall effect due to shift type. In Exp. II, a replication of Exp. I, 60 undergraduates learned R shifts faster than ED shifts, but overtraining had no discernible effect. Results were compared with those reported by Nolan and were discussed in terms of a 2-stage attention model of discrimination learning. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer of a discrimination by pigeons (Columba livia) between pictured locations and the represented environments.

In Exp 1, pigeons (Columba livia) were trained in a successive slide presentation procedure to discriminate between pictures of 2 ends of a room and then trained to find food in the actual room. A congruent-transfer (CT) group learned the spatial discrimination more quickly than an incongruent-transfer (IT) group. In Exp 2's replication we used a simultaneous slide presentation procedure and added a control group. The IT group required significantly more trials than the CT or control groups. In Exp 3, order of the training conditions was reversed. CT and IT conditions had no effect on the speed of acquisition of the discrimination. This indicates that pigeons acquire a representation of spatial locations from pictures, which can then direct behavior, but the direction of transfer observed was unidirectional. This suggests that a discrimination between spatial locations may not be accurately represented in pictorial form. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relative pitch perception is constrained by absolute pitch in songbirds (Mimus, Molothrus, and Sturnus).

Assessed the ability of starlings (Sturnus vulgaris), cowbirds (Molothrus ater), and a mockingbird (Mimus polyglottos) to maintain a relative pitch discrimination when the absolute frequencies of a serial pattern of tones were changed. In Exp I, 7 Ss learned a relative pitch discrimination between 4-tone sequences that either ascended or descended in frequency within a 1-octave range. Results show that Ss lost the discrimination completely when the frequency range was shifted an octave above or below the initial training range. Recovery of the discrimination in the novel ranges was slow, and considerable relearning was necessary. Starling Ss, however, easily generalized the relative pitch discrimination to new frequencies within the original training range. In Exp II, 4 starlings were trained on the same relative ascending–descending discrimination in 2 noncontiguous frequency ranges. Ss lost the discrimination when transferred into a novel gap of frequencies between the original training ranges. Findings demonstrate that songbirds can learn a relational discrimination between serial pitch patterns but that their ability to generalize the discrimination is constrained markedly by the frequency range in which the sound sequences are learned initially. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-dependent improvement in passive avoidance learning of the young chick: Cholinergic mediation?

Studied cholinergic mediation of the age-dependent improvement in response suppression of the young chick by determining the performance of 144 Vantress?×?Arbor Acre 4-day-old chicks, pretreated with scopolamine (SCO), during passive avoidance (PA) and extinction testing. In Exp I, Ss were trained to keypeck for heat reward (prepunishment training), and then tested for PA learning under immediate, 2-sec-delayed, or no shock condition. Half of the Ss in each condition received saline injections before prepunishment training and .5 mg/kg SCO injections after training. The rest received .5 mg/kg SCO injections both before and after training. For Ss in both SCO groups, delaying shock onset resulted in significantly less response suppression than immediate response-contingent shock. In Exp II, 4-day-old Ss injected with saline or SCO were trained to keypeck for heat reward and then tested for resistance to extinction under response-contingent shock or nonshock conditions. Punishment decreased the number of extinction responses for both saline and SCO groups. Results indicte that the age-dependent improvement in response suppression of the young chick cannot be explained solely by a significant increase in central cholinergic functioning. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task specificity in nonspecific transfer and in extradimensional stimulus generalization in pigeons.

Determined whether discrimination training per se is sufficient to produce positive nonspecific transfer and whether it sharpens extradimensional stimulus-generalization gradients, using domestic pigeons. In Exp I, 8 groups of Ss received true-discrimination (TD) or pseudodiscrimination training between 2 line orientations in either (a) a successive-conditional (SC) discrimination prior to transfer to a true SC or (b) a go/no go (GN) discrimination between 2 colors. Discriminative performance in transfer was facilitated only when the original and transfer discriminations were of the same type. Exp II showed that positive nonspecific transfer was primarily mediated by the transfer of task-specific learning rather than by the transfer of attentiveness. In Exp III, 4 groups were trained as in Stage 1 of Exps I and II and given single-stimulus training with a chromatic stimulus, followed by a wavelength stimulus generalization test. Only TD-GN discrimination training produced sharp gradients, an effect leading to the conclusion that GN discrimination training and stimulus generalization are closely related by task requirements rather than by attention. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Positive transfer from sequence production to sequence discrimination in a nonverbal organism.

Examined the relation between a pigeon's ability to produce and to recognize a particular arbitrary sequence of arbitrary elements, in 3 experiments involving a total of 100 naive male White Carneaux pigeons. In Exp I, 16 Ss were trained to discriminate sequences composed of 3 successively presented colors (A, B, and C). A yes response was rewarded for identifying A?→?B?→?C sequences; a no response for identifying non-A?→?B?→?C sequences. Exp II showed that the acquisition of this discrimination was facilitated by prior training on the production of the sequence A?→?B?→?C. Exp III showed that the facilitation of the discrimination of A?→?B?→?C sequences observed in Exp II could be attributed specifically to knowledge of the order of the elements A, B, and C that was acquired during the production of the sequence A?→?B?→?C. The control conditions of Exp III were (a) a pseudo-production task in which the Ss pecked the colors A, B, and C as presented successively; (b) a nonsequential task that established discriminative performance with respect to A, B, and C; (c) pseudo-production training that was preceded by discrimination training; and (d) training to produce either the sequence C?→?B?→?A or B?→?A?→?C. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overtraining and reversal learning in the rat: Effects of stimulus salience and response strategies.

Observed an overtraining reversal effect (ORE) in Exp I in 16 female hooded rats trained to discriminate horizontal from vertical stripes in the jumping stand. Overtraining was also found to produce a change in Ss' response strategy (the pattern of movements the Ss make before they jump). In Exp II, light and dark grays were the stimuli. Overtraining produced a different response strategy and no ORE was found. Results present a difficulty for the 2-stage attentional analysis of the ORE which predicts that the ORE is less likely to be found with the striped stimuli than with the gray. They provide some support, however, for a 2-stage account in which 1 stage is taken to be an overt observing response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lack of task specificity and absence of posttraining effects of atropine on learning.

Three experiments, with 91 male Lister rats, examined the effect of the cholinergic antagonist atropine on the acquisition of learning tasks known to be sensitive or insensitive to impairment by hippocampal lesions, on the retention of performance acquired in the absence of the drug, and on memory consolidation immediately after daily training trials. In Exp I, intraperitoneal atropine sulfate (10 or 50 mg/kg) injected 30 min prior to training severely impaired learning of both spatial and nonspatial discrimination tasks when compared with saline or atropine methylnitrate (50 mg/kg). In Exp II, atropine sulfate (50 mg/kg) also impaired spatial discrimination accuracy in Ss previously trained to asymptote under drug-free conditions. These deficits were not due to either peripheral drug effects of gross sensorimotor impairments. In Exp III, daily posttraining injections of atropine sulfate (50 mg/kg) failed to influence either learning or subsequent retention of place navigation in Ss trained to find a single hidden escape platform. The data confirm that profound learning deficits occur when training is conducted under atropine but offer no support to the hypotheses that cholinergic neurons play an important role in memory consolidation or other posttraining processes. Results demonstrate dissimilarities between the behavioral impairments induced by cholinergic blockade and hippocampal lesions under appropriate test regimes. (50 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired equivalence and distinctiveness in matching to sample by pigeons: Mediation by reinforcer-specific expectancies.

Assessed the ability of a reinforcer to mediate an association between 2 stimuli that independently predict the occurrence of that reinforcer (acquired equivalence of cues). In Exp I, 12 male White Carneaux pigeons were trained on shape (plus and circle) and color (red and green) matching-to-sample tasks. Correct responses were systematically reinforced with corn on some trials and wheat on others to establish associations between 1 stimulus from each task and a "common" outcome. Following training, Ss were transferred to a symbolic matching-to-sample task wherein a stimulus from one training task was presented as the sample, and the stimuli from the other training task were presented as comparisons. In the 1st session, experimental Ss made significantly more correct responses than controls (i.e., Ss "matched" stimuli previously associated with a common outcome). Exp II with 18 Ss replicated this acquired equivalence effect and controlled for food preference. Delayed matching-to-sample training demonstrated enhanced memory performance for Ss exposed to different reinforcement contingencies, but this effect was confined to the shape task. Results indicate that a reinforcer can serve as the basis for organizing otherwise unpaired predictive cues in memory and that animals will selectively use differential expectancies as cues for solving complex discrimination tasks, depending on the difficulty of the discrimination. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The reward value of light increment under supranormal and subnormal arousal.

2 Experiments, with 80 male Wistar rats each, studied the effects of methamphetamine and pentobarbital, respectively, on the reward value of light increment, alternating training days with test days to separate learning effects from performance effects. During the 1st wk. of Exp. I, if injected on training days with saline solution, Ss trained with light increment performed more responses on test days than Ss trained without light increment but, if injected with methamphetamine, Ss trained with light increment performed fewer responses. During the 2nd wk., training with light increment became relatively more effective for those trained under 2 or 3 mg/kg of methamphetamine but less effective in Ss with 0 or 1 mg/kg. In Exp. II, the difference in number of test-day responses between Ss trained with and without light increment decreased when pentobarbital injections (5, 10, 15, or 20 mg/kg) were administered on training days. In both experiments, more responses were performed on training days by Ss receiving light increments, and the number of responses varied inversely with doses of drugs. Results complement previous findings and indicating that the reward value of an indifferent stimulus depends on an interaction between the arousal value of the stimulus and arousal level of the organism. (French summary) (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of visual interference in delayed matching-to-sample with pigeons.

In 2 experiments, independent groups of pigeons were trained on an identity matching task involving line orientations as sample and comparison stimuli. An overhead houselight was illuminated continuously throughout each training session or was never illuminated during training sessions. During subsequent testing, the lighting conditions during the delay were the same as in training on some trials, but on other trials they were opposite those of training during either the entire delay (Exp 1) or during a portion of the delay (Exp 2). In Ss trained with the houselight off, turning the houselight on during the delay produced a large and enduring disruption in matching accuracy. In Ss trained with the houselight on, turning the houselight off during the delay produced only a moderate and temporary disruption in matching accuracy. In pigeons, as in monkeys, sustained retroactive interference effects obtain only when the level of illumination is increased during the delay interval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative effects of US preexposure: Modulation of conditioned responding by an excitatory training context.

Conducted 2 experiments with 120 naive Sprague-Dawley rats to examine factors that contribute to retarded emergence of conditioned responding to a conditioned stimulus/stimuli (CS) trained in a context in which unsignaled unconditioned stimulus/stimuli (UCS) had previously been administered. In both experiments, water-deprived Ss were used in a conditioned lick suppression task to measure the conditioned response (CR) elicitation potential of the CS and the training context. From Exp I, it was determined that nonreinforced exposure to the excitatory context after UCS preexposure and prior to CS–UCS pairings in that context eliminated the CR deficit observed on a subsequent test of the CS. From Exp II, it was determined that the recovery induced by contextual deflation after CS training was specific to deflation of the context in which the CS was trained as opposed to another excitatory context. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control after extradimensional training in pigeons: A comparison of response contingent and noncontingent training procedures.

In an experiment with a total of 32 White Carneaux pigeons, 2 groups of Ss for which reinforcement was procured by keypecking were given true discrimination (TD) or pseudodiscrimination (PD) training with different colors of the house light before they were taught to peck at a display of 3 vertical lines and tested on the line orientation continuum. 2 other groups were trained in the same way except that no response was required during discrimination training. Of the latter groups, the TD-trained Ss acquired the keypecking response (with autoshaping) more quickly than the PD-trained Ss. Their generalization gradients did not differ. Of the former groups, the TD-trained Ss produced a steeper generalization gradient than the PD-trained Ss. These results suggest that (a) general transfer effects are produced by TD and PD training and (b) differential stimulus control resulting from these procedures is mediated by the operation of response-produced cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of varied reward schedules on generalized persistence of rats.

Gave concurrent acquisition training to 4 groups of male albino rats (N = 70) in 2 parallel runways, such that continuous reward (CR) occurred in 1 alley and varied reward (VR) occurred in the other. The varied reward conditions were partial reward (PR), partial delay (PD), variable magnitude (VM), and constant delay (CD). A CR control group received CR in both alleys. All Ss were extinguished in the alley which had previously been associated with CR. Using resistance to extinction in the CR runway as the index of generalized persistence, the groups were ordered from greatest to least persistence as follows: PR, PD, VM, CD, and CR. This specific ordering is most easily accommodated by an elaboration of stimulus-aftereffects theory. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Young children's (Homo sapiens) understanding of knowledge formation in themselves and others.

Three- and 4-yr-old children were tested for comprehension of knowledge formation. In Exp 1, 34 Ss watched as a surprise was hidden under 1 of 4 obscured cups. The experimenter then pointed to the cup. All children searched under the correct cup, but no 3-yr-olds (in contrast to most 4-yr-olds) could explain how they knew where to look. Ss then discriminated between simultaneous pointing by 2 adults, one who had hidden a surprise and one who had left the room before the surprise was hidden. Most 4-yr-olds (but no 3-yr-olds) showed clear discrimination between the adults. In Exp 2, 16 Ss were tested with procedures designed to make the source of their own knowledge more obvious, but this had no effect on performance. It is concluded that studies using very similar procedures with chimpanzees and rhesus macaques were measuring an ability (or inability) to understand how knowledge states form. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of visual restriction in rats on generalization along the dimension of angular orientation.

Trained 60 light- and 60 dark-reared Long-Evans hooded rats on discriminations involving angular orientation of single rectangles or pairs of rectangles. 102 other Ss were trained on a pattern (N vs. X) discrimination. No significant differences were found between visually experienced and inexperienced Ss either in their acquisition of any of the orientation problems or in their ability to generalize after training along the dimension of angular orientation. A significant difference due to rearing condition was observed for acquisition of the pattern discrimination and generalization following training. Findings are discussed in terms of further specification of the effects of visual deprivation and their implications with regard to models of shape recognition in the rat. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)