Inhibitory effect of a steroidal antiestrogen (EM-170) on estrone-stimulated growth of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinoma in the rat

Rats were trained on a successive delayed conditional discrimination task measuring memory for magnitude of reinforcement. In the study phase of the task, the rats were given one of two cereals. One cereal contained 25% sugar; the other 50% sugar. One of the two cereals was always designated the positive stimulus and the other the negative stimulus. This study phase was followed by the test phase in which the rat was shown an object which covered a food well. If the rat was given the negative stimulus in the study phase of the trial, no food reward was placed beneath the object. Whenever the positive stimulus was presented a food reward was available beneath the object. Performance was measured as the latency to uncover the food well. After reaching criterion level, the rats were given amygdala, hippocampal, or control lesions. Amygdala-lesioned rats showed significant deficits in performance, whereas no long-term deficits were observed for the hippocampal-lesioned groups even at longer retention delays. In additional experiments, it was shown that amygdala-lesioned, like normal, rats had similar taste preferences. Finally, normal and hippocampal-, but not amygdala-, lesioned rats transferred readily to different cereals containing 25% or 50% sugar. Thus, it appears that the amygdala, but not the hippocampus, plays a significant role in explicit data-based or working memory for affect information based on magnitude of reinforcement.     

Effect of classical conditioning on an internal clock.

Six experiments with 53 male Charles River rats used a psychophysical choice procedure to study the internal clock used to discriminate duration and to investigate whether this clock is sensitive to the signal value (associative strength) of a stimulus. The experiments involved 2 types of trials: On choice trials, a stimulus lasted a short (e.g., 3-sec) or long (e.g., 12-sec) duration; Ss then chose between 2 levers. The rewarded choice depended on the duration of the stimulus. On conditioning trials, the stimulus used on choice trials was presented, but it ended without food (extinction trials) or with food (pairing trials) regardless of what the S did. The main measure of performance was short bias, defined as accuracy with the short stimulus without a corresponding accuracy with the long stimulus. Exp I showed that extinction trials increased short bias relative to training without conditioning trials or to training with pairing trials. Exps II–VI tested explanations of these results. The same results were found when extinction trials were the same duration as the short stimulus (Exp II), when extinction trials were a random duration (Exp V), and when the signal value of the CS was changed in another way (Exp VI). The effect of conditioning trials was modality specific (Exps III and IV). It is concluded that, of the explanations considered, the most valid is that changing the signal value of a stimulus changes how the clock times the stimulus. Reducing signal value reduces the measured duration. (54 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Intermittency of reinforcement during NA trials and performance on the ambiguous-cue problem.

In 2 experiments a total of 16 White Carneaux and 6 Autosexer female pigeons were trained on the ambiguous-cue problem which is a 2-choice discrimination task involving 3 stimuli: positive (P), ambiguous (A), and negative (N). The 2 types of trials--PA (during which P and A are simultaneously present and the correct choice is P) and NA (during which N and A are simultaneously present and the correct choice is A)--were presented in mixed order; each trial terminated after 1 response. As the intermittency of reinforcement for choosing A on NA trials was increased, performance on (and acquisition of) the PA trials improved greatly and eventually equalled (and in some instances surpassed) that on the NA trials. Performance on NA trials was only slightly affected, if at all. (French summary) (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Marking in pigeons: The role of memory in delayed reinforcement.

A previous study by the 1st author and colleagues (see record 1980-27237-001) showed that if reinforcement is delayed, rats find it difficult to learn the correct path through a maze, but learning improves dramatically if a brief tone or light is presented after every choice response. The marking hypothesis suggests that the unexpected stimulus directs attention to the preceding response, thereby marking it in memory. To explore the generality of this phenomenon, in the present 4 experiments 102 pigeons were reinforced after a delay for pecking half of a split key. A change in key color following a choice response produced significantly greater learning than did no marker or one following a response during the intertrial interval (Exp I), though an immediate marker was only slightly more effective than one delayed 3 sec (Exp II). In Exps III and IV, the marker followed either a correct or an incorrect response on food trials, and whichever response was marked increased substantially. Marking thus appears to be a robust and powerful phenomenon, capable of substantially modifying behavior in a variety of species and settings. Reasons why markers may sometimes interfere with learning rather than enhance it are suggested. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The negative suggestion effect: Pondering incorrect alternatives may be hazardous to your knowledge.

This article examines the negative suggestion effect, or the impact of exposure to incorrect alternatives on memory for correct information. All experiments used the following design: (a) cued-recall test of general facts (e.g., "second smallest planet") with immediate correct feedback, (b) interpolated exposure to incorrect information related to Test 1 items, and (c) a second test over the same items as Test 1. Test 2 was either multiple choice or cued recall and was given either immediately or 1 week after interpolation. Three experiments confirmed the existence of negative suggestion: Exposure to misinformation hindered subsequent performance on those items, relative to noninterpolated control items. The magnitude of this decrement is unrelated to retention interval, type of second test, number of incorrect alternatives exposed, and number of repetitions of incorrect alternatives. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Directed forgetting and intratrial interference in pigeon delayed matching.

In 3 experiments, 4 Silver King pigeons were tested in an intratrial interference preparation in which 2 stimuli (red and green fields) were presented successively as samples and then simultaneously as comparison stimuli. Choice of the comparison matching the 2nd sample was designated correct and was reinforced. On different trials, either the 1st or 2nd sample was followed by a cue to forget (horizontal line), and the alternate sample was followed by a cue to remember (vertical line). Relative to baseline trials in which both samples were followed by a cue to remember, accuracy was enhanced on trials in which the forget cue was presented immediately following the 1st sample and was reduced on trials in which the cue was presented following the 2nd sample. It is concluded that the context-retrieval interpretation of directed forgetting does not account for this pattern of findings; the rehearsal interpretation of directed forgetting provides a ready account of the data, an account tested and supported in the 3rd experiment. (French abstract) (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proactive interference effects on short-term memory in rats: I. Basic parameters and drug effects.

An operant delayed-matching task was used to assess the role of proactive interference (PI) effects on short-term memory capacity of rats. Task performance was analyzed in terms of the influence of the sample positions and response choices on previous trials. PI was predominantly attributable to the influence of the immediately previous trial but not preceding trials and was abolished by increasing the intertrial intervals from 5 to 15 sec. Nicotine induced a decline in choice accuracy only on trials in which the previous response had been to the side opposite the current sample and correct response, suggesting an increased susceptibility to PI. Physostigmine induced a mild, relatively nonspecific decline in response accuracy. Clonidine induced delay-dependent impairments irrespective of responses on previous trials. None of these drugs enhanced choice accuracy at any dose tested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do pigeons (Columba livia) study for a test?

In 4 experiments, the authors asked whether pigeons (Columba livia) would show metamemory by choosing to study a sample stimulus before taking a memory test. In Experiments 1a–1c, pigeons chose between cues that led either to exposure to a sample stimulus or directly to the comparison test stimuli without seeing the sample in a delayed matching-to-sample task. The same choice was used in Experiment 2 to see whether pigeons would take a reminder when memory of the sample was weak. In Experiments 3 and 4, pigeons’ responses led to either a choice between red and green side keys with a sample present to guide the choice or a choice with no sample present. The findings of all of these experiments suggest the absence of metamemory in pigeons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forced-choice: Are forensic interviewers asking the right questions?

In spite of exhortations to the contrary, forensic interviewers typically ask forced-choice questions, especially yes/ no and multiple-choice. In this study, older (4.8–5.1 yrs) and younger (3.2–4.4 yrs) preschoolers' responses to yes/ no and multiple choice questions were compared. For yes/no questions, half were correctly answered by "yes" and half by 'no." For 2-option multiple-choice questions, the first option was correct for a third of them, the second option was correct for another third, and neither option was correct for the remainder. Both older and younger preschoolers demonstrated a response bias toward saying "yes" to yes/no questions; they did not exhibit response biases for multiple-choice questions, choosing the two given options equivalently often. When neither option was correct, they more frequently said "I don't know", especially younger preschoolers. "I don't know" was almost never given in response to yes/ no questions. Furthermore, instructions allowing "I don't know" had no effect. These results have implications for forensic interviews; they suggest that responses to yes/ no questions are more unreliable and information from them more suspect than responses to multiple-choice questions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A postsample cue to forget does initiate an active forgetting process in pigeons.

Remember (R)- and forget (F)-cued training trials differed in whether the sample stimulus was or was not relevant to predicting trial outcome. Delayed matching-to-sample (DMTS) accuracy was lower on trials in which the F, rather than the R, cue followed sample presentation (F-cue effect). Because both types of training trials involved the same probability of end-of-trial reinforcement and pattern of discriminated test responding, the F-cue effect could not result from the F cue triggering negative affect, indiscriminate responding, failure to attend to test stimuli, or a pattern of responding incompatible with accurate DMTS performance. Results also revealed that the F-cue effect was not solely caused by presentation of an unexpected test stimulus. It was concluded that reduced accuracy on F-cued DMTS trials reflected the operation of an active forgetting process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing models of delayed sequence discrimination in pigeons: The advance key procedure.

In 2-event delayed sequence discrimination (DSD) training, one arrangement (temporal order) of 2 sample stimuli is the positive sequence and the remaining are the negative sequences for keypecking during a subsequent test stimulus. Three models of the DSD task were tested in 2 experiments with 8 White Carneaux pigeons. In Exp I Ss were allowed to terminate a trial by pecking the "advance key" during the sample stimuli or to let the test stimulus progress to the next trial. In the absence of a peck to the advance key, the trial continued to the completion of the test stimulus. In Exp II, Ss were forced to choose actively between advancing to the next trial and continuing through the current trial. Choice between the advance and continue keys was required with the occurrence of each of the successive sample stimuli and the test stimulus. Although the addition of forced choice resulted in more uniform effects, Ss were able to identify negative sample sequences with the occurrence of the 1st negative sample event in both experiments. Results support the prospective memory model but not the retrospective and hybrid models of temporal sequence recognition in the 2-event DSD task. (French abstract) (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Finding comfort in a joke: Consolatory effects of humor through cognitive distraction.

This study aimed to demonstrate that the cognitive demands involved in humor processing can attenuate negative emotions. A primary aspect of humor is that it poses cognitive demands needed for incongruency resolution. On the basis of findings that cognitive distraction prevents mood-congruent processing, the authors hypothesized that humorous stimuli attenuate negative emotions to a greater extent than do equally positive nonhumorous stimuli. To test this idea, the authors used a modified version of the picture-viewing paradigm of L. F. Van Dillen and S. L. Koole (2007). Participants viewed neutral, mildly negative, and strongly negative pictures, followed by either a humorous or an equally positive nonhumorous stimulus, and then rated their feelings. Participants reported less negative feelings in both mildly and strongly negative trials with humorous positive stimuli than with nonhumorous positive stimuli. Humor did not differentially affect emotions in the neutral trials. Stimuli that posed greater cognitive demands were more effective in regulating negative emotions than less demanding stimuli. These findings fully support Van Dillen and Koole’s working memory model of distraction from negative mood and suggest that humor may attenuate negative emotions as a result of cognitive distraction. (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)     

Treatment of coccidioidal spinal infection: experience in 16 cases

A model of frontal inhibition in hypnosis was elucidated by examining with cortical evoked potentials error negativity and positivity in 23 low versus medium/high hypnotisables during a perceptual task which included trials with conflicting stimulus information. In susceptible subjects the number of correct responses was found to be smaller for trials with incongruent stimulus information with hypnosis when compared with baseline. While the early negative wave to incorrect responses tended to be higher in susceptible subjects, this wave was no longer followed by a late positivity, posited to reflect a failure to process further the error-related information. The results with hypnosis are interpreted as a failure of context updating without a global deficit in supervisory attention.     

Rate of forgetting in H.M.: 6-month recognition.

Picture-recognition performance of H.M. and 6 controls was evaluated 6 mo after initial learning, using materials from an earlier study in which the S received additional study time in order to equate his yes–no and delayed-match-to-sample (DMS) performance 10 min after learning to that of control Ss. In the present study, 6-mo recognition performance was assessed with no intervening exposure to target items. The S performed at chance levels when tested using the standard yes–no recognition procedure. When the yes–no procedure was modified so that distractor stimuli required positive responses, performance was comparable with that of controls. In addition, the S's DMS and delayed-nonmatch-to-sample performance were comparable with that of controls 6 mo after learning. Conclusions regarding the S's 6-mo recognition performance are thus dependent on the procedures used to assess memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oddity learning in the pigeon as a function of the number of incorrect alternatives

Pigeons' rate of learning a two-color oddity task increased as a function of the number of incorrect alternatives from 2 to 24 in Experiments 1, 2, and 3. In general, pigeons that were transferred from many-incorrect-alternative to two-incorrect-alternative oddity performed better than controls, but considerably below baseline (Experiments 2 and 3). In Experiment 4, pigeons showed no unconditioned tendency to peck the odd stimulus among 24 incorect alternatives, when pecks were nondifferentially reinforced, and in Experiment 5, when this procedure was preceded by oddity training, a progressive drop in odd-stimulus pecking was found. In Experiment 6, pigeons exposed to a nine-stimulus array in which the odd stimulus appeared (a) in the center or (b) separate from the array learned faster than when the odd stimulus was at the edge. This outcome suggests ththe figure-ground relation between the odd stimulus and the incorrect alternatives plays a role in the facilitation produced by increasing the number of incorrect alternatives but that poor performance on the standard, three-alternative oddity task appears to be due to center-odd trials which provide a difficult size or number discrimination.     

Control of Matching by Differential Outcome Expectancies in the Absence of Differential Sample-Outcome Associations: A serial compound view.

In this study, pigeons learned 2 separate one-to-many conditional discriminations in which they matched form samples to line and hue comparisons. Correct choices within each comparison dimension yielded differential (food vs. no-food) outcomes that were not predictable from the samples alone. At asymptote, latency to make a correct choice was shorter when food was the contingent outcome than when no food was the outcome. More important, when the samples from each task were subsequently exchanged, comparison choice varied systematically as a function of the sample and the set of new comparison alternatives that followed them. Together, these results indicate that choices were cued by differential outcome expectancies arising from serial compounds consisting of each sample and the dimensional characteristics of the comparisons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the role of differential sample behaviors in matching-to-sample.

In 3 experiments, 8 White Carneaux pigeons were trained on matching-to-sample (MTS) with differential sample-response requirements (SRRs) that were identical with respect to 2 pairs of sample stimuli but either correlated or uncorrelated with correct choice. Ss in the uncorrelated condition were slower to reach criterion levels of accuracy than Ss in the correlated condition in spite of their equivalent sample discriminations. However, correlated Ss were more disrupted in their matching performances than the uncorrelated Ss when subsequently switched to nondifferential SRRs. Differential sample behaviors (DSBs) also generated higher levels of accuracy on delayed MTS when correlated with choice, and accuracy in this condition did not differ as a function of whether the samples were hues or lines. However, sample dimension did affect memory performance in the uncorrelated condition. Reversing differential SRRs for 1 pair of samples substantially reduced matching accuracy in the correlated group but had almost no effect in the uncorrelated group. Findings demonstrate that DSBs directly control pigeons' matching performances and also overshadow conditional stimulus control by the samples when these behaviors are predictive of correct choice. The facilitation in matching produced by DSBs apparently arises from the additional cue these behaviors provide. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term object recognition memory in the rat: Nonmatching with trial-unique junk stimuli.

A delayed nonmatching-to-sample (DNMS) task with trial-unique stimuli, similar to that used to test object recognition memory in primates, was adapted for use with rats. For each trial of the DNMS task, two stimuli were randomly selected from a pool of 250 small "junk" objects; one member of the pair was designated as the sample. On the first part of a trial, the rat traversed an elevated runway and displaced the sample for food reward. After a 10-s delay, the rat again traversed the runway to choose between the previously presented sample and the second member of the pair. Reward on the choice trial followed selection of the new object. Scores on the first day of DNMS were significantly above chance, and animals could consistently perform at approximately 75% accuracy. Extending the delay to 30 or 120 s lowered choice accuracy, but performance was still above chance. The DNMS task for rats, unlike most other memory tests for rodents, does not require memory for spatial location. The similarity to tests used with primates should allow for more direct comparison of results of memory research across species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Word recognition cues in children: The relative use of graphemic cues, orthographic cues, and grapheme-phoneme correspondence rules.

Pre-readers and children with varying amounts of reading experience were shown a stimulus word (or nonword) followed by four response alternatives that varied in similarity to the target stimulus. The response alternatives varied in terms of graphemic similarity to the target, the extent to which they conformed to English orthography, and the extent to which they sounded like the target stimulus. Initially, children were asked to choose the response alternative that was "most like" the target stimulus. On subsequent trials, they were asked to choose the alternative that "sounded like" or "looked like" the target. Pre-readers and beginning readers were very inflexible in their choices and chose response alternatives that looked like the target quite independently of the instructions. Children with 3 years of reading experience also chose alternatives that looked like the stimulus in the initial ambiguous task, but were able to choose the alternative sounding like the target when instructed to do so. Children with 5 years of reading experience initially chose alternatives that sounded like the target stimulus, but when instructed to do so, chose alternatives that looked like the target. (PsycINFO Database Record (c) 2010 APA, all rights reserved)