Interaction of Pavlovian conditioning with a zero operant contingency: Chronic exposure to signaled inescapable shock maintains learned helplessness effects.

Four studies, with 372 male Holtzman rats, examined the effect of Pavlovian contingencies and a zero operant contingency (i.e., uncontrollability) on subsequent shock-escape acquisition in the shuttle box using triads consisting of escapable-shock (ES), yoked inescapable-shock (IS), and no-shock (NS) rats. After exposure to 50 signals and shocks per session for 9 sessions, interference with shuttlebox escape acquisition for IS Ss was a monotonically increasing function of the percentage of signal–shock pairings during training (Exp I), with 50% pairings producing little or no impairment. Without regard to signaling, ES Ss performed as well as NS Ss. Exp II demonstrated that training and test conditions led to substantial and equal impairment in IS Ss preexposed for 1 session to 100 or 50% signal–shock pairings or to unsignaled shocks. In Exp III, chronic exposure to 100% signaled ISs resulted in impairment only if the signal (light) was present during the shuttlebox test. The continuous presence of the signal during the test contrasted with its discrete (5-sec) presentation during training and suggested that an antagonistic physiological reaction rather than a specific competing motor response had been conditioned. Exp IV provided evidence for possible conditioned opioid mediation. Findings suggest that chronic exposure to uncontrollable shocks maintains the impairment produced by acute exposure only if the shocks are adequately signaled. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast effects in escape conditioning of rats.

In Exp I 39 male Holtzman albino rats ran for 20 trials from an alley where they received .2-, .4-, or .8-ma shocks to a goal box where there was no shock. All Ss were then shifted to .4 ma in the alley for 20 trials. Results show that rapid adjustment of running speeds occurred with shifts in amount of escapable shock. More importantly, however, positive and negative contrast occurred. In Exp I an experimental group (n = 10) received .2 ma on half of the trials and .4 ma on the other half, and 2 control groups (n = 10) received either .4 or .2 ma on all trials. Results show that the experimental group escaped faster on .4-ma trials than the .4-ma control group (positive contrast) and escaped more slowly on .2-ma trials than the .2-ma control (negative contrast). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure to learn to escape in rats previously exposed to inescapable shock depends on nature of escape response.

Results of previous studies show that dogs exposed to inescapable shocks in a Pavlov harness subsequently fail to learn to escape shock in a shuttle box. The present 6 experiments attempted to replicate this finding with male Sprague-Dawley rats (N = 182). In agreement with many previous investigations, Exp I found that Ss exposed to inescapable shock did not fail to learn to escape in a shuttle box. Exp II, III, and IV varied the number, intensity, and temporal interval between inescapable shocks and did not find failure to learn in the shuttle box. An analysis of responding in the shuttle box revealed that Ss shuttled rapidly from the very 1st trial, whereas dogs acquire shuttling more gradually. Exp V and VI revealed that Ss exposed to inescapable shock failed to learn to escape when the escape response was one that was acquired more gradually. Exp V utilized a double crossing of the shuttle box as the escape response and Exp VI utilized a wheel-turn response. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intertrial reinstatement of training stimuli on complex maze learning in rats: Evidence that "acquisition" curves reflect more than acquisition.

In Exps I–III (224 male Sprague-Dawley rats), Ss were run in a complex maze to escape weak footshock or to approach an appetitive reinforcer. Extramaze intertrial reinstatement of the same reinforcer as that used in training was found to enhance subsequent maze performance. Exp IV (80 Ss) determined that appetitively and aversively motivated performance benefitted from brief intertrial exposures to the start box of the maze. In Exp V (64 Ss), a facilitatory effect indicated that memory trace activity need not be maintained between training and reinstatement or between reinstatement and subsequent training. Exp VI (80 Ss) examined the effects of reinstatement at the beginning, middle, or end of 5-min intertrial intervals and found enhanced performance in the last 2 conditions. Exp VII (24 Ss) established that 4 successive reinstatement treatments without interpolated training trials were no more beneficial than a single reinstatement. Exp VIII (16 Ss) determined that forgetting had occurred over the standard 5-min interval between training trials. Exp IX (32 Ss) found that reinstatement alleviated forgetting that had already transpired. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Catecholamine depletion in mice upon reexposure to stress: Mediation of the escape deficits produced by inescapable shock.

Reports 9 experiments with 372 male Swiss-Webster mice in which, immediately following exposure to 60 inescapable shocks, Ss had significantly reduced hypothalamic norepinephrine (NE). Within 24 hrs NE levels returned to control values. Reexposure to as few as 10 shocks 24 hrs after initial stress exposure resulted in significant decline of NE. At this interval after shock, escape performance was severely disrupted, with a large proportion of Ss exhibiting numerous failures to escape shock. Increasing brain dopamine (DA) and NE by levodopa treatment prior to shock prevented the escape deficits. Conversely, pairing 5 inescapable shocks with NE depletion by FLA-63, or both DA and NE depletion by alpha-methylparatyrosine, disrupted escape performance 24 hrs later. Residual drug effects, state dependence, or sustained amine turnover could not account for the behavioral changes. Data are discussed in terms of catecholamine mediation of escape performance through variations in response maintenance abilities. It is suggested that long-term effects of inescapable shock may be due to sensitization effects or conditioned amine depletion. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned helplessness in the rat.

4 experiments, using a total of 159 male albino Sprague-Dawley rats, attempted to produce behavior in the rat parallel to the behavior characteristic of learned helplessness in the dog. When Ss received escapable, inescapable, or no shock and were later tested in jump-up escape, both inescapable and no-shock controls failed to escape. When barpressing, rather than jumping up, was used as the tested escape response, fixed ratio (FR) 3 was interfered with by inescapable shock, but not lesser ratios. With FR-3, the no-shock control escaped well. Interference with escape was a function of the inescapability of shock and not shock per se: Ss that were "put through" and learned a prior jump-up escape did not become passive, but their yoked, inescapable partners did. It is concluded that rats, as well as dogs, fail to escape shock as a function of prior inescapability, exhibiting learned helplessness. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Controllability and duration of stress alter central nervous system depressant-induced sleep time in rats.

Rats were exposed to either 80 escapable shocks or yoked inescapable shocks and then injected with several hypnotic doses of sodium pentobarbital, midazolam, or ethanol; their sleep-time duration was compared with that of naive controls. Inescapable shock exposure resulted in a significant increase in ethanol-induced sleep time compared with the escapable shock and naive control groups. Both escape and yoked groups showed an increase in barbiturate-induced sleep time compared with controls, although no difference was observed for midazolam. Acute stress (20 5-sec inescapable shocks) did not alter the depressant-induced sleep time for any of the drugs tested. These results illustrate the importance of psychological aspects of stress and its influence on the potency of certain depressants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arousal of frustration following gradual reductions in reward magnitude in rats.

16 male Holtzman rats were assigned to each of 4 groups; Ss were given a 14-pellet reward for 60 runway acquisition trials. During a subsequent 18-trial shift phase, one group was shifted to a 1-pellet reward on Trial 1, a 2nd was shifted on Trial 13, and a 3rd was given 1 less pellet each trial and then 1 pellet for the last 6 trials. The speeds of all 3 groups decreased to a level below that of a control group given a 1-pellet reward throughout training. All Ss were then given hurdle-jump training to escape from the 1-pellet reward to a neutral box. All 3 shifted groups showed acquisition of the response, whereas the control group did not. Results indicate that both gradual and abrupt reward reductions arouse frustration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to uncontrollable stress alters withdrawal from morphine.

Examined the influence of the controllability/uncontrollability of shock as a stressor on the severity of subsequent morphine withdrawal in 2 experiments with 84 male Holtzman rats. In Exp I (36 Ss), Ss that received 2 daily sessions of 80 yoked-inescapable shocks, in contrast to those given 80 escapable shocks or restrained without shock, showed an enhanced series of correlated withdrawal behaviors (i.e., mouthing, teeth chattering, head/body shakes) 24 hrs later when injected with morphine sulfate (5 mg/kg) followed by a naloxone HCl (5 mg/kg) challenge. In Exp II (48 Ss), this finding was replicated with escape-yoked-restrained Ss given saline injections during the pretreatment phase, but the impact that inescapable shock had on later precipitated withdrawal was completely blocked when Ss were administered naltrexone HCl (14 mg/kg) before each shock session. Findings are discussed in terms of the capability of inescapable shock to activate an endogenous opiate system, thereby leading to a sensitization of release or receptor processes that could protentiate later morphine withdrawal. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned helplessness in the gerbil?

27 male Mongolian gerbils were assigned to escapable, inescapable, and control groups and subjected to 2 consecutive days of jump-up escape followed 24 hrs later by testing in a barpress escape task. Reliable differences occurred between escapable and inescapable Ss and between inescapable and control Ss. Findings provide evidence of learned helplessness in Mongolian gerbils. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Escape/avoidance responding in rats depends on strain and number of inescapable preshocks.

2 experiments examined escape-avoidance responding in a 1-way jump box following exposure to signaled, inescapable shock. In Exp I with 24 female Long-Evans rats, the occurrence of failures to escape and to avoid was an increasing function of the number of preshocks, over a range of 75-275, with a pronounced interference effect occurring after 225 and 275 preshocks. In Exp II with 10 Long-Evans (noninbred) and 10 Fischer (inbred) female rats, there were large differences between strains in failures both to escape and to avoid following 225 preshocks. Long-Evans Ss were severely retarded, whereas Fischer Ss were disrupted only during the initial trials. Findings demonstrate the importance of strain and number of preshocks in controlling the interference effect in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Magnitude and shift of reward in instrumental aversive learning in rats.

Conducted 3 experiments in which 4 groups of female hooded rats (N = 192) were given 35 classical fear-conditioning trials in 1 side of a 2-compartment box. Ss were then allowed to jump a hurdle to the adjacent box and escape the fear-eliciting stimuli. Reward magnitude (fear reduction) during hurdle jumping for 2 groups was either large or small throughout while for 2 groups it was increased or decreased after some training. Manipulated and nonmanipulated reward varied between experiments. Preshift performance was better with large than with small reward. Positive contrast effects were not found, but a negative contrast effect was obtained in Exp. III. The concepts of incentive motivation and frustration, used to account for performance in appetitively motivated learning tasks, are applied to the findings. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeon memory: Same/different concept learning, serial probe recognition acquisition, and probe delay effects on the serial-position function.

In Exp I, 2 White Carneaux pigeons were trained with sets of 70 pairs of color-slide stimuli in a same/different task to perform at least 88% correct; 6 different sets were used in successive acquisitions. Ss transferred same/different performance to novel stimuli with 60% accuracy following their 6 acquisitions; further training and daily changes in the training stimuli revealed 71% transfer to novel stimuli. In Exps II and III, 4 Ss were trained (88% criterion) in a serial-probe-recognition task with 3 list items, and the list length was increased with successive acquisitions to 4, 5, and 6 items. Their serial-position functions changed for different delays between the last list item and the test item revealing a recency effect (last items remembered well) for 0-sec delay, recency and primacy effects (first items remembered well) for 1- and 2-sec delays, and only a primacy effect for a 10-sec delay. Results are discussed in relation to human memory performance and theories of memory processing. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of punishing active avoidance in young and adult rats.

Examined whether age-related differences in suppression occur when a learned response is punished. 8 groups of weanling and adult male Holtzman rats (N = 96) received active-avoidance training and subsequent punishment for that response. Following active avoidance, Ss were assigned to a regular extinction group or to 1 of 3 punishment-delay (0-, 2-, or 10-sec.) groups, which received shock in the goal box. Although weanlings and adults were equivalent in active-avoidance acquisition, under the immediate punishment condition immature Ss required significantly more trials to learn passive avoidance. A delay-of-punishment gradient was obtained in adults but not in weanlings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Glossolalia as learned behavior: An experimental demonstration.

60 18–44 yr old undergraduates listened to a 60-sec sample of glossolalia (defined to them as pseudolanguage) and then attempted to produce glossolalia on a 30-sec baseline trial. Afterward, half of the Ss received 2 training sessions that included audio- and videotaped samples of glossolalia interspersed with opportunities to practice glossolalia. Also, live modeling of glossolalia, direct instruction, and encouragement were provided by an experimenter. Both the trained Ss and untreated controls attempted to produce glossolalia on a 30-sec posttest trial. About 20% of Ss exhibited fluent glossolalia on the baseline trial, and training significantly enhanced fluency. 70% of trained Ss spoke fluent glossolalia on the posttest. Findings are more consistent with social learning than with altered state conceptions of glossolalia. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning and extinction of avoidance and escape behavior in neonatal dogs.

Ran 16 neonatal purebred beagles for 6.5 days in a 1-way shuttle box with cold air as the aversive stimulus. 8 Ss started at 1 day of age and 4 each started at 2 and 3 days of age. 8 Ss received escape conditioning and 8 received avoidance conditioning. Following this training, both groups were given a series of extinction trials. Both escape and avoidance conditioning and extinction were obtained. Findings are comparable to previous avoidance findings in neonatal dogs and superior to findings on neonatal mice and kittens. Results display quantitative properties found in studies of adult rats and especially adult dogs. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal learned helplessness and physiologic response to infant crying.

Exposed 49 mothers of 3–4 mo old infants to varying degrees of control over the termination of a tape of infant crying. Each S received 1 of 3 instrumental pretreatments: (a) escape—4 buttonpresses terminated the infant cry, (b) inescape—buttonpress was unrelated to cry termination, and (c) control—mothers passively listened to the cry. Following pretreatment, each S was given an instrumental shuttlebox task consisting of a solvable task with an alternation response that controlled cry termination. Cardiac responses were monitored throughout the session. Ss pretreated with inescapable infant crying showed debilitated performance on the 2nd task. Failure to escape, number of trials to escape criterion, and latency of response to the cry were all greater for the inescape group. In addition, only Ss with prior experience controlling the cry showed cardiac deceleration, an index of attentional processing, during a 10-sec anticipatory period preceding the cry episode of the solvable instrumental task. These cardiac data provide evidence that the important behavioral differences may in part be attributable to differential processing of cues signaling the onset of crying. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of memory in the neonatal mouse.

Conducted 4 experiments with Swiss-Webster mice (N = 488) to examine the development of memory of an escape response between 3-11 days of age. Ss were given 25 training trials in a straight-alley escape task and then retested at various retention intervals. Results show that 5- and 7-day-old Ss had a retention capacity of less than 6 hr. At 9 days of age, however, retention capacity greatly increased to at least 96 hr., suggesting that a period of maturational development critical to long-term memory processes occurs at 9 days of age in the neonatal mouse. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Weight regulation with palatable food and liquids in rats with lateral hypothalamic lesions.

Maintained 25 female Carworth CFE albino rats with 4- or 7-sec 1-ma bilateral lesions of the lateral hypothalamus (LH) for 87 days on a high-fat diet and a sequence of fluids (water, 6% sucrose, and 1 or .2% saccharin). Lesioned Ss reached a greater weight than 9 sham-lesioned Ss offered the same diet and fluids, and maintained greater weight regardless of the fluid offered. These data do not support the hypothesis that LH lesions lower the set point for weight. Rather, the finickiness of LH Ss results in smaller intake of unpalatable foods and water which, in turn, results in stablization of weight below that of controls. If sufficiently hydrated, LH Ss eat greater quantities of highly palatable foods than do controls, resulting in greater body weight. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is empathic emotion a source of altruistic motivation?

Tested the hypothesis that empathy leads to altruistic rather than egoistic motivation to help. 44 female college students watched another female undergraduate receive electric shocks and were then given a chance to help her by taking the remaining shocks themselves. In each of 2 experiments, Ss' empathic emotion (low vs high) and their ease of escape from continuing to watch the victim suffer if they did not help (easy vs difficult) were manipulated in a 2?×?2 design. It was reasoned that if empathy led to altruistic motivation, Ss feeling a high degree of empathy for the victim should be as ready to help when escape without helping was easy as when it was difficult. But if empathy led to egoistic motivation, Ss feeling empathy should be more ready to help when escape was difficult than when it was easy. Results followed the former pattern when empathy was high and the latter pattern when empathy was low, supporting the hypothesis that empathy leads to altruistic rather than egoistic motivation to help. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)