Prolonged duration of the “novelty effect” following prolonged exposure to a single discriminandum

Rats were exposed for approximately 1 month to a single stimulus mounted on the home cage wall. During discrimination training, half of the Ss had the exposed figure as the positive stimulus and half the exposed figure as the negative stimulus. Control Ss had no pattern mounted on the wall. The results indicate that when the exposed figure was the positive stimulus, the Ss made significantly more errors than the control Ss. but when the exposed figure was the negative stimulus, the Ss made significantly fewer errors. These results are consistent with the exploratory literature, which suggests that exposure to a stimulus will reduce the invitational properties of that stimulus relative to a more novel stimulus and thereby will affect the probability of selecting one stimulus over another, at least for a period of time, in a discrimination task.     

Acquired equivalence and generalized suppression in a virtual reality environment

Acquired equivalence was investigated using a virtual reality conditioned suppression task administered in a first-person-shooter game. Two visual cues, A1 and B1, were followed by a tone (O1), and another two cues, A2 and B2, were followed by another tone (O2). During differential Pavlovian conditioning, A1 was paired with an instructed unconditioned stimulus (US) consisting of a flashing white screen, whereas A2 was not. All cues and outcomes were then presented at test, in the absence of the US, and suppression ratios were calculated for multiple response topographies (shots, hits, and breaks). Clear evidence of the suppression of shots was seen for A1 and B1, with no suppression being seen for either A2 or B2. Presentations of O1 and O2 resulted in significant suppression of shots and hits, whereas only O1 led to the suppression of breaks. The US expectancy ratings were consistent with these behavioral results. The findings are discussed in the light of differing accounts of acquired equivalence.     

Second-order conditioning of the conditioned emotional response: Some methodological considerations

Employing rats in a CER procedure, the present study sought to determine the extent to which the second-order conditioning effects reported by Rizley and Rescorla (1972) represented first-rather than second-order conditioning. Subjects receiving first-order pairings of flashing light (CS₁) and shock followed by second-order pairings of noise (CS₂) and CS₁ displayed greater suppression to CS₂ than did control subjects receiving second-order pairings in the absence of first-order conditioning. This was true whether or not control subjects had experienced unsignaled shock or habituation to CS₁ prior to CS₂CS₁ pairings. Simple stimulus pairings did produce some suppression to CS₂, however. The procedure developed by Rizley and Rescorla (1972) appears to be a reliable means for producing and studying second-order aversive conditioning.     

Failure to block control by a relevant stimulus

Pigeons were trained to depress a treadle in the presence of a discriminative stimulus, either a tone or illumination of red houselights, in order to obtain access to grain or avoid electric shock. In avoidance training, the auditory discriminative stimulus yielded faster acquisition than did the visual one. In appetitive training, the visual discriminative stimulus yielded faster acquisition than the auditory one. Experiments 2 and 3 used these stimuli in Kamin’s (1969) blocking design. In Experiment 2, when the pigeons were trained to depress a treadle in the presence of tone to obtain grain and then red light was added as the redundant stimulus, the light acquired stimulus control over treadlepressing; blocking was not observed. In Experiment 3, when the pigeons were trained to depress a treadle in the presence of red light to avoid electric shock and then tone was added as the redundant stimulus, the tone acquired stimulus control over treadle-pressing. Again, blocking was not observed. The implications of these results for several models of stimulus control are discussed.     

Covariation in conditioned response strength between stimuli trained in compound

Conditioned lick suppression by water-deprived rats was used to elaborate on recent evidence that the attenuated conditioned response elicited by an overshadowed stimulus may be enhanced by extinction of the overshadowing stimulus with which it had been trained in simultaneous compound. Using a modified serial stimulus arrangement in which a light coexisted with the last half of a tone that terminated with footshock, it was found in Experiment 1 that the tone overshadowed the light. Extinction of the tone-shock association resulted in a virtually complete recovery of the response to the overshadowed light. Using this serial overshadowing procedure, the possibility that the strength of a conditioned response to an element trained in compound covaries as a function of the strength of the response to the other element was tested in Experiment 2. Following overshadowing training similar to that of Experiment 1, independent reinforcement of the overshadowed light, that is, associative inflation, was found to have no deleterious effect on the response to the overshadowing tone. This suggests that the effects of postconditioning extinction and inflation of one element do not have symmetrical effects upon responding to the other element. The results of Experiment 2 were replicated in Experiment 3 using a simultaneous compound stimulus as opposed to the serial compound of the previous studies. These results are discussed in terms of various associative and cognitive models of learning and performance.     

Conditioning of simultaneous and serial feature-positive discriminations

Three experiments with rat subjects examined the development of simultaneous and serial feature-positive discriminations in appetitive conditioning. In Experiment 1, reinforced presentations of a simultaneous light-tone compound were intermixed with nonreinforced presentations of either the light or the tone. The compound stimulus acquired conditioned behaviors of a form characteristic of the predictive feature alone; the element common to reinforced and nonreinforced trials did not evoke conditioned behavior. In Experiment 2, reinforced presentations of a serial light-trace-tone compound were intermixed with nonreinforced tone-alone presentations. The light feature stimulus acquired conditioned behaviors characteristic of visual CSs. The tone stimulus, common to reinforced and nonreinforced trials, evoked conditioned behaviors characteristic of auditory CSs, but only when preceded by the light. In Experiment 3, variations in the interval between the light and tone on reinforced trials had little effect on responding to the light CS but substantially altered the pattern of responding to the tone CS. These results suggested that simultaneous and serial feature-positive discriminations may be solved differently. Performance in simultaneous feature-positive discriminations may be determined solely by associations between the feature stimulus and the reinforcer, but performance in serial discriminations may also involve the acquisition of a conditional cue function to the feature.     

Extinction of enhanced latent inhibition

Hungry rats were used in a classical conditioning procedure in which visual stimuli were paired with food. Conditions in which nonreinforced exposure to a nontarget stimulus was followed by exposure to a simultaneous compound nontarget/target stimulus (a blocking procedure) resulted in enhanced latent inhibition to the target relative to exposure to the nontarget, followed by exposure to the target stimulus alone. A third phase of nonreinforced exposure training, in which the target was exposed alone following the compound, reduced levels of latent inhibition relative to results obtained with the blocking procedure. Experiments also suggested that this was not the result of restoration of associability by the omission of an expected presentation of the nontarget stimulus in the final preexposure phase. These results suggest that enhanced latent inhibition is due to summation of a direct-target-no-event association and a second-order association of these elements via target-nontarget and nontarget-no-event association. Exposure to the target after compound exposure extinguished the target-nontarget association and reduced the sources of no-event learning for the target.     

Modification of acoustic and nociceptive reflexes in the rat by visual stimulation

Three experiments demonstrated in the rat that the flexor reaction to a nociceptive cutaneous stimulus (a .5-msec, .5-mA electric shock to the feet) was inhibited by a preceding light flash. In the first, the optimal lead time was at 50 or 100 msec compared to separations of 5 or 400 msec. In the second, the inhibitory effect was shown in ambient noise approximating threshold, indicating that the response decrement was not caused because the light may have blocked a facilitating effect of a moderate background noise level. In the third experiment, the light flash inhibited both the flexor reaction to the cutaneous stimulus and to an acoustic startle stimulus with which it was randomly intermixed. These findings reveal that inhibition is not specific to a particular modality of eliciting stimulus input, though it may be restricted to a particular class of motor events, that is, to flexor reactions.     

道路交叉口信号控制系统取消黄灯的分析与思考

阐述了黄灯的产生与作用,指出黄灯使用中存在的系列问题,对取消黄灯的可行性和科学性进行了分析,提出了取消黄灯,实施绿灯3秒闪烁措施,可有效减少道路交叉路口事故隐患,保证路人及行车安全的建议.     

Conditions of preexposure and passive avoidance behavior in rats

In the first experiment, rats given a 5-min period of preexposure (simple exploration) to a two-compartment box showed poorer passive avoidance of the compartment where they were subsequently shocked than a control group which was not preexposed to the apparatus. The second experiment involved preexposure to sugared milk (SM), flashing light and loud noise (LN), or simply the apparatus (EC). One group received no exposure to the apparatus (NC). Following one shock trial, the groups were ordered LN > NC > EC > SM from most to least passive avoidance. The results were discussed in the context of latent inhibition and an averaging model of positive and negative events.     

Contextual effects in latent inhibition with an appetitive conditioning procedure

In three experiments, rats received presentations of a diffuse 30-sec stimulus (a light) and of food, and their tendency to enter the food tray was monitored. Experiment 1 showed that when the light was made to signal the delivery of food, the response of entering the food tray increased in frequency during the stimulus. The acquisition of this conditioned response to the light was retarded in subjects that had received preexposure to the stimulus. In Experiments 2 and 3, subjects received preexposure to the stimulus, some in the same context as that subsequently used for stimulus-food pairings and some in a different context. Those experiencing the change of context acquired the response more readily. It is argued that these results demonstrate a latent inhibition effect that is attenuated by contextual change.     

The Role of Visual Indicators in Dual Sensory Mode Instruction

Advances in our knowledge of the structure of working memory suggest that under some circumstances, effectively more processing capacity is available to learners if instructional materials use multiple information modes (e.g. auditory and visual) instead of equivalent single mode formats. This paper examined this modality effect from a cognitive load perspective in three experiments using geometry instruction. In accordance with cognitive load theory, it was predicted that the additional processing capacity provided in an audio/visual format would only enhance learning if mental resources were not devoted to extensive visual based search in order to coordinate auditory and visual information. Using two different areas of geometry, Experiments 1 and 2 found that if visual search was clearly high, then audio‐visual instruction was only beneficial if visual indicators in the form of electronic flashing were incorporated into the instructional format. Under high search conditions, a standard audio/visual format without the aid of flashing proved no better than visual only instruction. Experiment 3 attempted to clarify earlier results by using instructional materials trivially low in visual search. Data indicated that a standard, audio‐visual format resulted in superior learning to a visual only format. There was no beneficial effect of electronic flashing in Experiment 3, suggesting that visual indicators were not necessary in areas of low visual search. It was concluded that cognitive load as determined by visual search established the effectiveness of visual indicators.     

Fear-potentiated startle using three conditioned stimulus modalities

The capacities of three different conditioned stimulus modalities (light, noise, and airflow produced by a fan) to produce fear-potentiated startle were evaluated. Previous experiments have shown that following either light-shock or noise-shock pairings, both the light and noise conditioned stimuli acquire the ability to potentiate the acoustically elicited startle response in rats (the so-calledfear-potentiated startle effect). In Experiment 1, the ability of airflow produced by a fan to act as a conditioned stimulus was investigated. Rats were given either paired or impaired fan-shock training followed by a test for fear-potentiated startle. The fan conditioned stimulus potentiated startle only in the group given explicit fan-shock pairings. In Experiment 2, we evaluated the discriminability of the three conditioned stimulus modalities. Rats were given light, noise, or fan-shock pairings and were subsequently tested for fear-potentiated startle with the trained conditioned stimulus as well as the two remaining novel conditioned stimuli. Only the trained conditioned stimulus potentiated startle. These results show that fear-potentiated startle can be produced with three discriminable conditioned stimulus modalities, allowing the future use of fear-potentiated startle in the investigation of higher order conditioning phenomena.     

Stimulus intensity affects pigeons’ timing behavior: Implications for an internal clock model

Five pigeons were trained to discriminate between 2- and 10-sec illuminations of a white light; choice of a red pecking key was correct and rewarded after presentation of the short stimulus, whereas choice of a green key was correct and rewarded after presentation of the long stimulus. On half the trials, the light was bright; on the others, it was dim. Durations of 4, 6, and 8 sec of both dim and bright light were also presented; choices on these trials were not rewarded. The probability of the pigeons’ choosing the short alternative decreased in a graded manner as duration of both bright and dim light increased from 2, to 4, to 6, to 8, and to 10 sec. However, the pigeons were more likely to choose the short alternative with longer durations of the dim light than the bright light, a result that implies that the perceived duration of a dim light was shorter than that of a bright light of equal length. One interpretation of this effect is that stimulus intensity affects the rate of the pacemaker in an internal clock mechanism subserving timing of event duration.     

The nature and determinants of spatial retreat in the pigeon between periodic grain presentations

Pigeons were exposed to fixed-time and fixed-interval schedules that ranged from 30 to 960 sec. The probability of a subject’s location in the rear of the chamber (away from the reinforcer dispenser) peaked during the postreinforcer period, and was referenced to proportional time between reinforcers. Increasing the interreinforcer interval generally increased time in the rear. In some sessions (Experiment 1), location in the rear produced an explicit stimulus change (altered the color and intensity of lights, i.e., time-out); this change increased time spent in the rear without affecting its temporal locus or its relation to the interreinforcer interval. During Experiment 2, a keypeck (near the reinforcer site) produced the explicit stimulus change used in Experiment 1. The characteristics of keypeck time-out resembled those of movement to the rear of the chamber (with and without an explicit stimulus change), suggesting that movement away from the reinforcer site is functionally homologous to keypeck time-out.     

Cross-modal transfer of stimulus control in the albino rat: A stimulus delay procedure

The present experiment demonstrated in a simultaneous discrete trial discrimination that the stimulus control of a rat’s leverpress response can be errorlessly transferred across stimulus modalities, i.e., from light to click location and from click to light location. Subsequent to acquisition of the original discrimination, the original and new discriminative stimuli were simultaneously presented for several sessions. Then the new discriminative stimulus was presented 3 sec prior to the onset of the original discriminative stimulus. Within the direction of transfer, e.g., from light to click location, the delay group emitted fewer trial and intertriai errors than the control group. As the new discriminative stimuli acquired control over responding, the response latency distributions were differentially affected. The results suggest that the transfer of control from the original to the new discriminative stimuli is mediated by the temporal aspects of the delay interval.     

Attraction to mobile and immobile conspecifics

Male and female laboratory rats invariably investigate a novel conspecific placed in their home cages. In Experiment 1, mature male rats were exposed in their home cages to active and inactive juvenile males. Inactive juveniles were pretreated with haloperidol to induce behavioral stasis in a normally upright, quadrupedal stance. In repeated daily observations, males exposed to active juveniles displayed significantly longer intervals of investigation than did males exposed to inactive juveniles. In Experiment 2, mature males and females were repeatedly exposed to active and inactive castrate females. Males investigated significantly longer than did females, active female castrates were investigated significantly longer than were inactive female castrates, and sex of subject interacted significantly with activity-nonactivity of the social stimulus animal. In Experiment 3, mature males and females were repeatedly exposed to active and inactive castrate males. Males investigated significantly longer than did females, active male castrates were investigated significantly longer than were inactive male castrates, and sex of subject interacted significantly with activity-nonactivity of the social stimulus animal. The results demonstrate that sexual dimorphism in persistence of social investigation may be interpreted as a sex difference in response to normal movement cues of a stimulus complex characterizing a conspecific.     

Stimulus control of immunization against chronic learned helplessness

Two experiments investigated the effectiveness of multiple (five) sessions of signaled eseapable-shock pretraining in preventing (immunizing against) the shack-escape impairment produced by an equal number of sessions of signaled inescapable shock. In Experiment 1, rats were exposed to 50 pairings per session of a white-noise stimulus with escapable shock during the immunization phase. Subsequently, they were exposed to 50 pairings per session of a different (houselight) stimulus with inescapable shock. Shock-escape performance in a shuttlebox test with constant illumination revealed no evidence of immunization relative to the performance of rats given five prior sessions of light-signaled inescapable shock only. Experiment 2 was identical in all respects to Experiment 1, except that both the escapable- and the inescapable-shock phases for animals in the immunization treatment group involved the same stimulus (houseüght) as a shock signal. Under these circumstances, the prior escapable-shock training significantly reduced the shuttle-box escape deficit engendered by chronic exposure to signaled inescapable shock; performance in the shuttle-box was not reliably different from that of rats exposed to signaled escapable shock alone. These findings suggest that, under chronic conditions, the development of stimulus control using Pavlovian conditioning procedures may serve to modulate the normally prophylactic influence on later shock-escape acquisition of serial exposure to escapable and inescapable shocks.     

Recovery from blocking achieved by extinguishing the blocking CS

Extinction-induced attenuation of single-phase and two-phase blocking was examined with rats in a conditioned lick-suppression task. In Experiment 1, which compared the effectiveness of single- and two-phase blocking, it was found that single-phase blocking was facilitated by the initiation of training with an A-US trial rather than an AX-US trial. Single-phase (but not two-phase) blocking was attenuated as a result of 200 extinction trials with the blocking stimulus (Experiment 2). Experiment 3 revealed recovery from two-phase blocking after 800 extinction trials with the blocking stimulus. Recovery from both types of blocking was specific to the blocked CS trained in compound with the extinguished stimulus (Experiment 4). This is the first article to report that the blocking deficit can be reversed by extinguishing the blocking stimulus. These results are discussed in light of acquisition models (i.e., retrospective revaluation) and expression models (i.e., the comparator hypothesis).     

Stimulus specificity of concurrent recovery in the rabbit nictitating membrane response

Three experiments demonstrated that, following the extinction of an established conditioned stimulus (CS; e.g., tone), the pairing of an orthogonal stimulus from another modality (e.g., light) with the unconditioned stimulus (US) results in strong recovery of responding to the extinguished CS. This recovery occurred to about an equal degree regardless of whether or not initial training contained unambiguous stimulus—reinforcer relationships—that is, consistent CS—US pairings—or some degree of ambiguity, including intramodal discrimination training, partial reinforcement, or even cross-modal discrimination training (tone vs. light). Experiments 1 and 2 demonstrated that this recovery of responding was largely specific to the extinguished CS, but moderate generalization to other stimuli from the same modality did appear. The results are discussed with reference to alternative mechanisms applicable to learning-dependent generalization between otherwise distinct CSs. These models assume that such generalization is mediated by either a shared response, shared reinforcer, shared context, or shared hidden units within a layered neural network. A specific layered network is proposed to explain the present results as well as other types of savings seen previously in conditioning of the rabbit nictitating membrane response.