Grasping in the pigeon (Columba livid): Stimulus control during conditioned and consummatory responses

Control of beak opening (gape) and peck location was examined in pigeons. Feeding pecks showed accurate guidance that positioned the seed between the beaks. At the moment of contact with the seed, gape was proportional to seed diameter, although pecks with gape less than seed diameter were more frequent following an increase in seed size during a meal. There were no substantial differences between pigeons trained to keypeck with autoshaping and those trained with operant conditioning procedures. With either procedure, water reinforcement produced keypecks with the beak closed; seed reinforcers of different sizes produced means for gape proportional to the seed diameters. Black or white circular stimuli of different sizes projected as conditioning signals had little influence upon gape, but a greater percentage of responses was directed to white stimuli. These results indicate that visual stimuli elicit and orient the peck, whereas the adjustment of gape also involves the somatosensory stimuli provided during previous experience with a particular reinforcer or food type.     

Directed forgetting in monkeys

Based on several recent demonstrations of a directed forgetting effect in pigeons, three experiments were carried out in an attempt to demonstrate directed forgetting in three squirrel monkeys. During initial training with a delayed matching-to-sample procedure, retention tests were always given for sample stimuli followed by remember cues (R-cues) and were always omitted for sample stimuli followed by forget cues (F-cues). Retention of F-cued items was tested on probe trials after initial training. The first two experiments examined the effects of R- and F-cues on memory for slide-projected pictures, with different pictures used on each trial of a session. In Experiment 1, a complex design was used in which one or two sample pictures were presented on each trial; when two pictures were presented, both could be R-cued or F-cued, or one could be R-cued and the other F-cued. A simpler design was used in Experiment 2, with only single pictures presented as sample stimuli and half the trials within a session R-cued and the other half F-cued. In both of these experiments, no differential retention of R- and F-cued stimuli was found, even at a retention interval as long as 16 sec. In Experiment 3, a series of studies was performed to test for directed forgetting when only two sample stimuli were used repeatedly throughout training and testing. With two pictures as sample stimuli, clear evidence of directed forgetting was found in Experiment 3b. It is suggested that the directed forgetting effect may arise only when a small set of sample stimuli is used.     

Attention and salience in associative blocking

The associative learning effect called blocking has previously been found in many cue-competition paradigms where all cues are of equal salience. Previous research by Hall, Mackintosh, Goodall, and dal Martello (1977) found that, in animals, salient cues were less likely to be blocked. Crucially, they also found that when the to-be-blocked cue was highly salient, the blocking cue would lose some control over responding. The present article extends these findings to humans and suggests that shifts in attention can explain the apparent loss of control by the previously learned cue. A connectionist model that implements attentional learning is shown to fit the main trends in the data. Model comparisons suggest that mere forgetting, implemented as weight decay, cannot explain the results.     

Directed forgetting in pigeons

Pigeons performed a version of delayed matching-to-sample in which different postsample cues signaled different trial outcomes. Cues to remember (R cues) signaled the usual comparison stimuli. Cues to forget (F cues) signaled either cancellation of comparison stimuli (comparison-omission) or presentation of a sample-independent discrimination (comparison-substitution). As assessed by occasional probe trials, F cues decreased matching accuracy during comparison-omission more than during comparison-substitution. The loss in accuracy of matching in F-cue probes was directly related to length of delays during comparison-omission but not during comparison-substitution. Because trials generally terminated in reward during comparison-substitution but not during comparison-omission, these findings were interpreted as suggesting the importance of end-of-trial reinforcement for the maintenance of short-term memory.     

Chromatic adaptation in the pigeon

This study presents evidence that adaptation to colored light alters the apparent hue of subsequently presented stimuli in pigeons. During training, right and left keypecks were reinforced following responses to colored and nominally achromatic slides, respectively. During test sessions, subjects continued to observe and report on the two classes of slides while 6-min components alternated, such that the experimental chamber was illuminated with either a green flood lamp or a nominally white bulb. The proportion of right keypecks following achromatic slides was much higher during green components than during white components, indicating that the achromatic slides appeared more like the chromatic slides.     

Imitation and social facilitation in the pigeon

The sight of another pigeon pecking a response key for grain resulted in similar pecking by more pigeons than did the sight of another pigeon eating or the sight of another pigeon (neither pecking nor eating). But more pigeons pecked the response key when they could see another pigeon that was neither pecking nor eating than when no other pigeon was there (whether or not key-light/grain pairings were observable in the adjacent compartment). Finally, observation of another pigeon pecking but not eating produced pecking comparable to observation of both pecking and eating. The presence of both imitation and social facilitation of keypecking were demonstrated. Observation of the consummatory response contributed little to keypecking.     

Stimulus preference and the transitivity of preference

Four pigeons were exposed to multiple schedules with concurrent variable interval (VI) components and then tested for preference transfer. Half of the pigeons were trained on a multiple concurrent VI 20-sec, VI 40-sec/cuncurrent VI 4G-sec5 VI 80-sec schedule. The remaining pigeons were trained on a multiple concurrent VI 80-sec, VI 40-sec/concurrent VI 40-sec, VI 20-sec schedule-After stability criteria for time and response proportions were simultaneously met, four preference transfer tests were conducted with the stimuli associated with the VI 40-sec schedules. During the transfer tests, each pigeon allocated a greater proportion of responses (M=0,79) and time (M=0.82) to the stimulus associated with the VI 40-sec schedule that was paired with the VI 80-sec schedule than lo the VI 40-sec schedule stimulus paired with the VI 20-sec schedule. Absolute reinforcement rates on the two VI 40 sec schedules were approximately equal and unlikely to account for the observed preference. Nor was the preference consistent with the differences in local reinforcement rates associated with the two stimuli. Instead, the results were interpreted in terms of the differential value that stimuli acquire as a function of previous pairings with alternative schedules of reinforcement.     

The development of forgetting and reminiscence

Many theoretical positions on memory development anticipate that forgetting rates should vary substantially with age. The nature of these age variations is also relevant to many applied questions about child development that have major social policy implications, such as the veracity of children's eyewitness testimony and the long-term effectiveness of classroom instruction. Surprisingly, developmental studies of long-term retention have repeatedly produced the puzzling finding that forgetting rates are age invariant. It now seems, however, that these null age trends may have been artifacts of variables such as measurement insensitivity, floor effects, and stages-of-learning confounds. Assuming, as some later studies suggest, that forgetting rates vary with age when these factors are controlled, there are three overriding questions that must be dealt with in the developmental analysis of forgetting: the relative importance of storage failure versus retrieval failure, the relative importance of true forgetting processes versus test-induced processes, and the relative importance of storage-based reminiscence versus retrieval-based reminiscence. We describe a framework (disintegration/redintegation theory) that provides a conceptual environment within which research on these questions can progress. This framework, which evolved from fuzzy-trace theory, reinterprets processes such as storage failure, retrieval failure, restorage, and retrieval relearning in terms of levels of featural integration in traces (i.e., the extent to which contextual information is integrated with core semantic gist to produce a coherent representation). The theory is implemented in a mathematical model (the trace-integrity model) whose parameters deliver measurements of relevant memory processes on a common ratio scale. In a series of experiments, the model was used to study the theory's predictions about the contributions of these memory processes to long-term retention in subjects between the ages of 7 and 70. All the experiments were standard long-term retention designs (an initial acquisition session, followed by a 1-2-week forgetting interval, followed by a series of retention tests).(ABSTRACT TRUNCATED AT 400 WORDS)     

Race salience and essentialist thinking in racial stereotype development

The authors explored the emergence and antecedents of racial stereotyping in 89 children ages 3-10 years. Children completed a number of matching and sorting tasks, including a measure designed to assess their knowledge and application of both positive and negative in-group and out-group stereotypes. Results indicate that children start to apply stereotypes to the out-group starting around 6 years of age. Controlling for a number of factors, 2 predictors contributed significantly toward uniquely explaining the use of these stereotypes: race salience (i.e., seeing and organizing by race) and essentialist thinking (i.e., believing that race cannot change). These results provide insight into how and when real-world interventions aimed at altering the acquisition of racial stereotypes may be implemented.     

Transfer of oddity learning in the pigeon

Two pigeons were trained on a six-key modified oddity-from-sample procedure. The stimuli were olor pictures of birds, butterflies, and human faces. Initially, the third peck on the sample key which presented one of three different bird pictures) lit only one comparison key. Every three dditional pecks on the sample illuminated another comparison key. Fifteen sample pecks produced he maximum of five comparison stimuli. A peck on the comparison key that presented the non-atching bird picture produced grain. Pecks on matching keys turned off all the comparison keys nd repeated the trial. The birds learned to peck each sample until the non-matching comparison timulus was produced, and then to peck that key. After acquisition (70%–90% accuracy), the hree bird stimuli were replaced by a new set of three bird pictures. Subsequent phases provided ew sets of bird, butterfly, and human face stimuli. Both birds showed transfer of oddity learning o the novel samples. The data suggest that the birds may have been engaging in conceptual-type oddity learning, rather than learning discrete five-key discriminations or a series of two component chains.     

Generalization of serial learning in the pigeon

Sequence learning in pigeons was studied in asimultaneous chaining paradigm: all stimuli and the opportunity to respond to each stimulus were available simultaneously. In contrast to the traditionalsuccessive chaining paradigm, a simultaneous chaining paradigm provides no differential feedback following each response (except the last). Subjects were first trained to perform on sequences of two (AB), then three (ABC), and then four colors (ABCD). Performance greatly exceeded that predicted by models of random choice. Generalization to novel arrays of three and four colors was complete. After training with a four-color sequence, the subjects were tested with subsequences consisting of all possible combinations of two and three of the four training colors (e.g., BD, AD, BC, ACD, BCD, etc.). The successful completion of these subsequences showed that the organization of the original sequence did not entail overt pecks to successive elements of that sequence. That subjects can respond accurately on nonadjacent subsets is not readily explained by a chaining theory, or by any theory that assumes that responding to element n provides a cue for responding to element n+1.     

Stimulus modality and short-term memory in rats

Two experimental paradigms are presented aimed at determining the retention of auditory and visual information over brief delay intervals. First, a conditional delayed matching-to-sample procedure was used in which rats were required to symbolically match the modality of the sample stimulus with one of two comparison stimuli. In the second experiment, subjects were trained and tested using a Konorski-type procedure. Despite the conceptual and procedural differences between the two procedures, subjects in both experiments showed steeper forgetting functions for visual events than for auditory events, while performance levels at 0-sec delay intervals were equivalent for both stimuli. These results, when taken together with related research conducted with pigeons, suggest that content of memory may have important influences on the short-term retention abilities of animal subjects.     

Stimulus variation and dimensional contrast

In two experiments, a maintained generalization procedure was employed to examine stimulus control of pigeons’ responses to a visual wavelength continuum. For both experiments, pigeons’ responses were periodically reinforced during wavelength values from one end of a continuum, while responses during other stimulus values were extinguished. In Experiment 1, the set of positive stimulus values remained constant, while the spacing of the set of negative stimuli varied. In Experiment 2, the set of negative stimulus values remained constant, while the spacing of positive stimuli varied. Positive dimensional contrast effects were obtained in both experiments. In general, the results indicated that variation in the spacing of negative stimuli had little effect on positive dimensional contrast. However, variation in the spacing of positive stimuli produced changes in the peak of the dimensional contrast gradient, without apparent change in the magnitude of the effect.     

Differential outcome expectancies and directed forgetting effects in pigeons

Pigeons were trained in a two-choice delayed matching-to-sample task with red and green hues. A brief postsample cue (a vertical or horizontal line) signaled whether the comparison stimuli would be presented or omitted on each trial. Comparison stimuli were always presented following the remember (R) cue, but never following the forget (F) cue or no-cue trials. One group of birds, the differential outcome (DO) group, received reinforcement with a probability of 1.0 for correct responses following one sample stimulus and a probability of 0.2 for correct responses following the other sample stimulus. The nondifferential outcome (NDO) group received reinforcement with a probability of 0.6 for correct responses to either stimulus. The effect of postsample cues was greater for the DO group than for the NDO group. Relative to the NDO group, the DO group displayed higher accuracy on R-cue trials and lower accuracy on F- and no-cue trials. Both tendencies contributed to the enhanced cue effectiveness obtained in the DO group. The results indicate that outcome expectancies are subject to maintenance rehearsal, which comes under the control of postsample R and F cues. They also suggest that maintenance rehearsal may be easier to sustain under DO conditions than under NDO conditions when a memory test is anticipated, but that it may be easier to terminate maintenance rehearsal under DO conditions when a memory test is not anticipated. The results are inconsistent with the assumption that the rehearsal of outcome expectancies is automatic.     

Stimulus change and complexity in exploratory behavior

It has recently been proposed (Fowler, 1967, 1971) that the incentive value of novelty can be defined in terms of stimulus change. An experiment is reported which examines the relationship between changes in complexity and the consequent exploratory behavior. Following extended exposure to a midcomplexity stimulus, rats were allowed to choose between a stimulus change and the now familiar midcomplexity stimulus. For some Ss the change was to a stimulus of higher complexity, and for others the change was to a lower complexity stimulus. The results suggest that physical stimulus changes to a stimulus of greater complexity is a more effective novel stimulus than physical stimulus changes to lesser complexity, although both changes may function as incentives.     

Stimulus competition in the absence of compound conditioning

Most associative theories have assumed that stimulus competition occurs only between conditioned stimuli (CSs) that are trained in compound. The present research investigated the possibility of competition between two CSs that were individually paired to the same unconditioned stimulus (US). We used human subjects in an anticipatory suppression analogue to Pavlovian conditioning. Experiment 1 showed that X+ training followed by A+ training resulted in impaired responding to X. This did not occur when A+ training preceded X+ training. Experiment 2 replicated the basic effect and showed that it did not occur when the Phase 2 training consisted of A? instead of A+ nor when the A+ pairings occurred in a second context. Experiment 3 showed that A+ pairings occurring in a second context could still produce the effect when X was tested in the context in which the A+ pairings had occurred, but not when X was tested in a context different from that used for A+ training. Collectively, these results suggest that individually trained CSs may compete with each other when one of those CSs is more strongly activated by the test context than the other one.     

激励手段在企业管理中的运用

人的需要是多种多样的。一般来说,当人的一系列需要得到满足时,积极性能够得到充分发挥。企业管理应当灵活运用各种激励手段,满足职工的不同需要,促进企业的发展。章阐述了激励手段在企业管理中的作用以及如何运用激励手段激发职工的积极性、主动性和创造性。     

Directed forgetting among third and seventh graders

The present studies examined the effectiveness of explicit and implicit Forget cues for enhancing memory of to-be-remembered items within a directed forgetting paradigm. Such a paradigm may be viewed as a laboratory analogue to a classroom testing situation where students read through an examination before beginning in order to cue themselves as to which information is important to remember. Subjects were third- and seventh-grade children. Evidence was provided that directed forgetting processes were operative at the time of recall so that memory enhancement did not merely reflect differential rehearsal of the to-be-remembered items during study. When easy partitioning of items into Remember and Forget sets was possible, subjects as young as third graders could benefit from postpresentation Forget cues. The data suggest that postpresentation Forget cues permit a selective search during recall and a consequent reduction in interference from to-be-forgotten items. Applications of these findings to a classroom testing situation were discussed.     

Stimulus selection in discriminative taste-aversion learning in the rat

In three experiments, rats were presented compound solutions consisting of a common element, saccharin, mixed with one of two different flavor elements, cinnamon and wintergreen. Rats in the experimental groups consistently received a toxicosis-inducing injection following one compound solution but not following the other compound solution. Rats in the control groups received toxicosis-inducing injections half the time following each of the compound solutions. After training in each experiment, there were tests for conditioning to the saccharin alone. The experimental groups drank significantly more than the control groups, indicating that the aversion to the partially reinforced saccharin in isolation was less when the different flavor cues were more highly correlated with reinforcement. In Experiment III, there was also a test for conditioning to the cinnamon or wintergreen flavor alone. The experimental group drank significantly less of the continuously reinforced flavor than the control group did of the partially reinforced flavor. These results are similar to those reported within more traditional conditioning paradigms.