Selective associations produced solely with appetitive contingencies: the stimulus-reinforcer interaction revisited

In studies reporting stimulus-reinforcer interactions in traditional conditioning paradigms, when a tone-light compound was associated with food the light gained stimulus control, but when the compound was paired with shock avoidance the tone gained control. However, the physical nature of the reinforcer-related events (food vs. shock) presented in the presence of the tone-light compound was always confounded with the conditioned hedonic value of the compound's presence relative to its absence. When the compound was paired with shock, its presence was negative relative to its absence (which was shock-free). In contrast, when the compound was paired with food, its presence was positive relative to its absence (which was food-free). The present experiment dealt with this confounding effect by conditioning a tone-light compound to be positive or negative, relative to its absence, solely with food reinforcement. One group of rats received food for responding in the presence of the tone-light compound and no food in its absence. The other group also responded in the presence of the compound, but received food only in its absence. These rats were trained on a chained schedule in which responding in the presence of the tone-light compound produced a terminal link signaled by the absence of the compound; responding ceased in the terminal link because it delayed food delivery. In a test session to assess stimulus control by the elements of the compound, tone and light were presented separately under extinction conditions. Rats that had been exposed to a positive correlation between food and the compound emitted almost double the responses in the presence of the light as in the presence of the tone. In comparison, rats that had been exposed to a negative correlation emitted only two thirds as many responses in the presence of the light as in the presence of the tone. Because this selective association was produced using only food, it appears that the contingencies under which a reinforcer is presented, rather than (or as well as) its physical properties, can generate the selective associations previously attributed to "stimulus-reinforcer interactions." This could mean that regardless of the class of reinforcer that ultimately maintains responding (appetitive or aversive), the contingency-generated hedonic value of the compound stimulus may influence the dominant modality of stimulus control.     

Communication of affect in "cooperative conditioning" of rhesus monkeys.

"Rhesus monkeys in primate chairs were conditioned to bar press within 6 seconds of presentation of a light in order to avoid electric shock. Following acquisition of this avoidance response two animals were placed facing each other and the bar was removed from the chair of one monkey and the stimulus light from the chair of the other. In order for either monkey to avoid shock a communication was necessary since neither animal had access to all elements of the problem. The results indicated that through nonverbal communication of affect an efficient mutual avoidance was performed. It was concluded that this paradigm is an exceptionally efficient and sensitive method for investigations of nonverbal communication." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Punished behavior: increases in responding after d-amphetamine

Responding maintained in squirrel monkeys under a 10-min fixed-interval schedule of food presentation was suppressed by presenting a shock after every 30th response (punishment). During alternate 10-min periods of the same experimental session, but in the presence of a different discriminative stimulus, responding either had no effect (extinction) or postponed delivery of an electric shock (avoidance). During sessions when the avoidance schedule was not in effect, d-amphetamine sulfate decreased punished responding. When the avoidance schedule was present during alternate 10-min periods, however, d-amphetamine (0.01 minus 0.56 mg/kg, i.m.) markedly increased responding during punishment components. Increases in responding during avoidance components were also evident. The effects of d-amphetamine on punished responding depend on the context in which that responding occurs.     

CS modality transfer of two-way avoidance in rats with central and basolateral amygdala lesions

Post-lesion acquisition of two-way avoidance and subsequent transfer to two warning signals (conditioned stimulus, CS) of different modality were investigated in 60 rats. In Experiment I the animals were originally trained with less salient (darkness) CS, then transferred to more salient compound (darkness and white noise), and finally to white noise CS. The opposite arrangement of the conditioned stimuli (CSi) during the subsequent stages was employed in Experiment II. In control animals, avoidance acquisition was faster and the intertrial responding (ITR) rate lower with the auditory than with the visual CS. Lesioned rats learned avoidance responses more slowly, independently of CS modality. The transfer to other CSi revealed dramatic between-group difference in the level and consistency of avoidance response, shuttle-box latencies and ITR rate. In control animals, transfer to more salient CSi enhanced avoidance performance, whereas change to less salient CS decreased it. Rather small changes in shuttle-box performance and consistency of avoidance response due to CS modality were seen in rats with the basolateral lesions. In contrast, central nucleus injury caused a strong deterioration in the avoidance transfer, especially when the visual CS followed the acoustic one. The results indicate differential involvement of the basolateral and central amygdala nuclei in stimulus-processing mechanisms of instrumental defensive behavior.     

The manipulation of dominance in monkeys with conditioned fear.

"2 group dominance tests were conducted on 10 rhesus monkeys. On the basis of these tests 5 pairs of animals adjacent, or nearly adjacent, in the hierarchy were given an additional 5 dominance determinations. The animal in each pair which received the greater number of raisins in each of the 7 tests between the 2 animals was designated as dominant. This animal in each pair was subjected to avoidance conditioning with this submissive partner as the conditioned stimulus… . The dominance status was found to be significantly reversed following the completion of conditioning. It was suggested that this observation provides behavioral evidence for the presence of fear in avoidance conditioning which is independent of the conditioning situation." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reinforcement versus species-specific defense reactions as determinants of avoidance barpressing.

In three experiments, rats whose escape and avoidance barpresses were reinforced by entering a safe floor in an otherwise shuttle conditioning arrangement (a shuttle barpress task) showed better learning than the rats that did not receive such reinforcement only when the shock intensity was very weak. Barpresses were found to have mostly nonfrontal topography and appeared not to be under the control of escape or avoidance contingency of reinforcement. Preavoidance training in which only frontal barpresses were allowed to terminate shock greatly facilitated avoidance responding and nullified the inverse effect of shock intensity. The findings were interpreted as indicating that innate defensive reactions play a more prominent role in avoidance behavior than reinforcement, but they do not appear to be as fixed and unmodifiable by learning as often suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sidman avoidance performance and response suppression in rats with septal lesions.

Ran 10 male Long-Evans hooded rats with septal lesions on 3 Sidman avoidance schedules which differed only in length of response-shock (RS) interval. Of the 5 septal Ss run on postoperative acquisition, all emitted responses at lower rates than the 5 controls, maintained shock rates equivalent to those of controls, and distributed their responses more efficiently than controls. Successive reductions in length of the RS interval produced suppression of avoidance responding in all Ss. However, for septal Ss, more sessions and a shorter RS interval were required to suppress avoidance responding. Performance of 5 Ss given preoperative experience was not changed by septal ablation. Both the lower response rate and the difficulty in suppressing avoidance responding are interpreted in terms of a deficit related to acquisition of stimulus control by conditioned aversive stimuli. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic correlates of chronic schizophrenia: A reaction time paradigm.

Assessed basal, tonic, and 2 phasic measures of heart rate and skin conductance among 16 drug-free, chronic, process, nonparanoid schizophrenics, and 2 groups of control Ss (hospital staff and prison inmates). Of particular interest were changes in autonomic activity that attended manipulation of "go" signal intensity within a reaction time paradigm. Among control Ss, increased signal intensity produced increases in tonic levels and amplitude of anticipatory responding. Among schizophrenics, however, the reverse occurred: Increased signal intensity resulted in decreased tonic levels and inhibition of anticipatory responding. Schizophrenic responses occurred in the absence of basal level differences between groups. Results are interpreted as indicating the presence of a learned anticipatory set that serves to reduce the impact of stimulus intensity. This inhibitory set would also appear to reduce receptivity to the cue component of stimuli. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Varying temporal contiguity and interference in a human avoidance task.

Temporal contiguity and number of interfering events were manipulated in a human avoidance (Martians) task, which required participants to prevent an “invasion” when a particular visual stimulus (“shield”) appeared by releasing the space bar before the shield was activated. A particular symbol, 1 of up to 6, functioned as a brief warning signal. The signal-offset to shield-onset (S-S) interval varied between groups, as did the number of additional symbols acting as distractors. In Experiments 1 and 2, speed of learning declined as a linear function of both trace interval and number of distractors. Path analysis showed that the effects of the S-S interval depended primarily on the number of distractors during this interval. Experiment 2 further demonstrated that participants who failed to suppress responding were generally unable to identify which symbol was the signal, suggesting that the presence of distractors disrupted detection of the contingency rather than performance. Overall, the results indicated that learning to associate 2 temporally separated events depends mainly on the amount of interference and little on the time interval between them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of exposure to conditioned stimulus and control of its termination in the extinction of avoidance behavior.

Describes 2 experiments in which, following signaled shuttle box avoidance training, a total of 52 female Fischer344 rats were exposed to the conditioned stimulus (CS) during no-shock treatment trials and subsequently tested during extinction trials in which shock was also absent. In Exp I, Ss that could control the termination of the CS during treatment responded significantly more often during extinction than yoked partners that received the same pattern and duration of CS exposure but could not control its termination. Exp II revealed that the probability of responding during extinction was a decreasing function of the duration of CS exposure during treatment. Thus, in the absence of shock, both lack of control over CS termination and increasing CS exposure each independently facilitated the weakening of well-established avoidance responses. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive conditioning in honeybees (Apis mellifera).

In Exps I–III, a shuttlebox was used, with the odor of formic acid as the aversive stimulus. A punishment contingency was found to suppress shuttling more in master animals than in yoked controls, whereas escape and unsignaled avoidance contingencies facilitated shuttling in master animals compared with yoked controls. In Exps III–VI, the Ss were unrestrained foragers flying back and forth between the hive and the sill of an open laboratory window to take sucrose solution from targets constructed so that shock could be delivered while the proboscis was in contact with the solution. A group of Ss trained to discriminate between 2 differently colored targets, one providing sucrose and the other sucrose plus immediate shock, performed as well as a group trained with sucrose and tap water and better than a group trained with sucrose and sucrose plus delayed shock. Ss for which a signal was paired with shock while they were feeding from a single target quickly learned to avoid the shock by flying off the target. The effectiveness of the pairing was demonstrated both by an explicitly unpaired procedure (which retarded acquisition when the signal and shock subsequently were paired) and by differential conditioning. Findings suggest that escape, punishment, and avoidance procedures appear to have the same effects on honeybees as on vertebrates. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: II. Without signal.

Manipulated independently the probabilities of aversive stimulus presentation given the occurrence or the nonocurrence of a leverpress response. 10 naive male rhesus monkeys (Macaca mulatta) were divided into 5 groups, each group receiving a different sequence of the 2 probabilities and thereby a different sequence of electric shock presentation schedules ranging between avoidance and punishment. The schedules provided systematic control both of the amount of response facilitation that occurred when response-produced shocks were first introduced following avoidance training and of the postfacilitation response rate decline. When the probability of shock presentation following a response was less than that for not responding, scalloped response patterns occurred; when the relative shock probabilities were reversed, bipeak response patterns were observed. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for a hierarchical structure underlying avoidance behavior.

In studies on avoidance learning, a warning signal is followed by an aversive unconditioned stimulus unless the participant performs a designated response. The authors examined whether avoidance behavior can be based on hierarchical knowledge, that is, knowledge about the conditions under which certain relations hold. In the present study, a single avoidance response had different effects depending on the nature of the warning signal. Results showed that participants acquired this hierarchical knowledge and used it to avoid negative outcomes. The results are in line with an occasion setting account of avoidance learning and can be explained also by a modified version of Lovibond's (2006) account of avoidance learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some effects of immediate versus randomly delayed shock on an instrumental response and cognitive processes.

"… Ss were required… to guess whether a right or left light would go on, indicating their guesses by pressing a lever below the appropriate light. Trials… [involved] non-shock… . [and] an immediate shock (IS) every time he pressed one lever and a randomly delayed shock (RDS) every time he pressed the other lever, irrespective of whether he guessed correctly or incorrectly." Results: a significant avoidance of the lever leading to RDS, a significantly greater number of Ss judged the RDS as more unpleasant than IS, a marked impairment of Ss' recall of stimulus events and their behavior during the shock trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of shuttle avoidance in young and adult rats.

Investigated stimulus generalization of 2-way active avoidance behavior in young and adult rats. In Exp. I with 12 adult and 12 young male Holtzman albino rats, CS frequency gained marked and comparable control over responding in both age groups; variation of background frequency prior to a no-tone CS, however, failed to exert any substantial control over avoidance behavior in either age group. In Exp. II with 12 Ss, Pavlovian frequency discrimination training was interpolated between acquisition of the shuttle response and generalization testing. Relative to their respective single stimulus control groups, the adult Ss showed a reliable peak shift in modal responding and the young Ss revealed a distortion in the gradient at frequency values on the side of CS+, opposite that of CS-. Although the occurrence of a peak shift was somewhat surprising in light of the fact that CS- here served as a "safety" signal, the data are interpreted as consistent with explanations of discrimination learning based upon the summation of excitatory and inhibitory gradients. In general, both experiments suggest that variations of CS frequency in an active avoidance situation tends to result in similar gradients for both young and adult Ss. The disparity between the present and previous findings are discussed in terms of the response requirements of the test situation. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative electrophysiologic findings between responders and nonresponders to class III antiarrhythmic drugs among patients with ventricular tachyarrhythmia

Rabbits received conditional discrimination training using contextual stimuli to set the occasion for stimulus pairings during eyelid conditioning. Specifically, animals were exposed to either the presence or the absence of an oscillating chamber light throughout the intertrial interval (50 +/- 10 s). For half the animals, this light signaled paired presentations of a discrete tone conditioned stimulus (CS) and air puff unconditioned stimulus (US) while darkness signaled presentations of only the tone CS. The remaining animals experienced the opposite contextual relationship to the conditioning stimuli. These trial types occurred pseudo-randomly across a session, with all transitions between contextual settings (i.e., light or dark) taking place immediately at the CS-US offset. Under these conditions, animals successfully utilized the contextual stimuli as conditional cues for differential responding to the shared CS. Moreover, both light and dark were equally effective as discriminative stimuli. A subset of animals received further training in which the contextual contingency was removed by restricting all conditioning to the CS-alone context. Without the contingency in place, subsequent CS presentations (paired and CS-alone) evoked equivalent conditioned responding across three sessions of training. Following the reinstatement of the contextual contingencies, discriminatory responding was immediately observed and returned to previous levels within three sessions. Finally, animals appeared to use the static representation of the conditional cue, rather than the phasic transition between cues, for discriminatory responding. These findings are discussed in terms of current neurobiological models of eyelid conditioning.     

Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: I. With signal.

Applied 2 independent probabilities of electric shock presentation to 12 naive male rhesus monkeys (Macaca mulatta) as the independent variables defining schedules of aversive control: (a) the probability that a fixed signal period would end with a shock if a specified response were made and (b) the probability that the fixed signal period would end with shock if a specified response were not made. Systematic changes in the probability values generated several familiar schedules of aversive control, as well as several intermittent procedures. Response rate tended to rise during the signal period when the probability values were set so that not responding was more likely to produce a shock than responding; response rate tended to fall during the signal period when the probabilities were set so that responding was more likely to produce shock than not responding. Response patterning in time was also evident during the interval between signals when no consequences were programmed. These characteristics of response patterning reflected the changes in the 2 independent probability variables in ways that simple measures of response rate and shock rate alone did not. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Picture fragment completion: Priming in the pigeon.

It has been suggested that the system behind implicit memory in humans is evolutionarily old and that animals should readily show priming. In Experiment 1, a picture fragment completion test was used to test priming in pigeons. After pecking a warning stimulus, pigeons were shown 2 partially obscured pictures from different categories and were always reinforced for choosing a picture from one of the categories. On control trials, the warning stimulus was a picture of some object (not from the S+ or S– category), on study trials the warning stimulus was a picture to be categorized on the next trial, and on test trials the warning stimulus was a randomly chosen picture and the S+ picture was the warning stimulus seen on the previous trial. Categorization was better on study and test trials than on control trials. Experiment 2 ruled out the possibility that the priming effect was caused by the pigeons' responding to familiarity by using warning stimuli from both S+ and S– categories. Experiment 3 investigated the time course of the priming effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potentiation, overshadowing, and prior exposure to inescapable shock.

Four experiments are reported which explore the possibility that prior exposure to inescapable shock alters the way in which animals process information from responding during subsequent escape training. The stimulus consequences of responding were manipulated in each experiment. Rats received escapable shock, yoked, inescapable shock, or no shock prior to fixed ratio-2 (FR-2) shuttle escape training. A novel change in illumination following each shuttle response had opposite effects on inescapably shocked and control subjects. It dramatically improved the performance of inescapably shocked rats but impaired the performance of restrained subjects. The signal had no effect on escape trained animals. Response-produced auditory cues following each lever press on an FR-3 lever-press escape task were also observed to improve learning in inescapably shocked rats but to impair learning in restrained controls. The relation between lever pressing and the exteroceptive cue was manipulated. The exteroceptive cue enhanced learning in inescapably shocked rats when any two of the three required lever presses produced the cue. In contrast, the performance of restrained animals was impaired whenever the third response of the FR-3 produced the cue. Otherwise performance was unimpaired. The implications of these results are discussed with respect to the phenomena of potentiation and overshadowing, as well as to ways in which prior exposure to inescapable shock might alter information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)