Opiate antagonists and long-term analgesic reaction induced by inescapable shock in rats.

Five experiments with 240 male albino rats examined the influence of opiate antagonists (naltrexone; 1–24 mg/kg, ip) on both the short-term analgesic reaction resulting 30 min after exposure to inescapable shock and the long-term analgesic reaction resulting after reexposure to shock 24 hrs after inescapable shock exposure. Exp I showed that the long-term analgesic reaction could be reduced by administration of naltrexone prior to exposure to inescapable tail shock. Exp II showed that the reduction in the long-term analgesic reaction produced by naltrexone was dose-dependent. Exp III showed that the long-term analgesic reaction could also be reduced by administration of naltrexone prior to reexposure to shock. Exp IV showed that the long-term analgesic reaction could be reduced by administration of a large dose of naloxone prior to reexposure to shock. Exp V showed that the short-term analgesic reaction was reduced by naltrexone administered prior to inescapable shock. Implications for the biochemical substrates of both learned helplessness and stress-induced analgesia are discussed. (56 ref) (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)     

Failure to learn to escape by rats previously exposed to inescapable shock is partly produced by associative interference.

2 experiments demonstrated that the effects of prior exposure to inescapable shock on the subsequent acquisition of an escape response in rats is determined by the nature of the contingency that exists between responding and shock termination during the escape learning task, and not by the amount of effort required to make the response or the amount of shock that the S is forced to receive during each trial. Exp I, using 48 male Simonsen rats, showed that inescapably shocked Ss did not learn to escape shock in a shuttle box if 2 crossings of the shuttle box were required (fixed ratio, FR, -2) to terminate shock, but did learn this FR-2 response if a brief interruption of shock occurs after the 1st crossing of the FR-2. Exp II with 72 Ss showed that inescapably shocked Ss learned a single-crossing escape response as rapidly as did controls, but were severely retarded if a brief delay in shock termination was arranged to follow the response. Results are discussed in terms of the learned helplessness hypothesis, which assumes that prior exposure to inescapable shock results in associative interference. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of response restriction during exposure to inescapable shock upon subsequent one-way and shuttle-avoidance performance in rats.

Investigated the effects of signaled inescapable shock on subsequent avoidance performance in 3 experiments with male Holtzman rats (N = 188). Exp I indicated that prior shock exposure (PSE) facilitated 1-way and shuttle avoidance. When Ss were preshocked in a harness so that free mobility was not possible, the facilitative effects of PSE on shuttle, but not 1-way avoidance performance, were largely reduced. Exp II indicated that activity during CS periods following PSE was greater among unrestrained than restrained Ss. Exp III showed that immobilization via injection of succinylcholine chloride did not affect the facilitative effects of PSE relative to that of Ss preshocked in a harness. Results are interpreted in terms of response repertoire changes produced by PSE in conjunction with the response requirement of the avoidance task. (French summary) (17 ref) (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)     

Effects of naltrexone and signaling inescapable electric shock on nociception and gastric lesions in rats.

Two experiments, with 144 male Long-Evans hooded rats, examined the antinociceptive effects of signaled shock and its physiological underpinnings. In Exp I, Ss were exposed to 1 of 3 shock conditions: no shock, unsignaled shock, and signaled (by a 10-sec, 1,000-Hz tone) shock. In each condition, Ss were tested hourly in the absence of tones for nociception, with vocalization to shock used as the behavioral measure. Ss receiving signaled shocks had stomach ulcer scores intermediate between those of no-shock and unsignaled shock Ss. Signaled-shock Ss also displayed a pronounced vocalization antinociception effect. This suggested that signaled shock may be less aversive. Exp II investigated a possible role of endogenous opiate peptides in these effects. Ss received hourly injections of either the opiate antagonist naltrexone (7 mg/kg, ip) or saline. There were no significant effects of naltrexone on either stomach pathology or nociception scores. The same effects of signaled shock were obtained as in Exp I. It is concluded that the role of endogenous opiates in the effects of signaled shock seen here is minimal. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in vulnerability to drug self-administration.

Recent evidence from both human and animal studies indicates that there are sex differences in all phases of the addiction process, including initiation and acquisition of use, patterns and levels of use, the progression to addiction, and relapse. This brief review summarizes a series of studies on sex differences in drug self-administration in rats on which the Wyeth Young Psychopharmacologist Award was based and relates these findings to human clinical data. Briefly, preclinical findings show that female rats acquire drug self-administration at a faster rate, work harder to obtain drug infusions, "binge" for longer initial periods of time and show a more diurnally dysregulated pattern of self-administration under extended-access conditions, and respond at higher levels under reinstatement testing conditions compared with male rats. Similar results have been reported in humans, suggesting a biological basis of sex differences in vulnerability to drug abuse. A number of biological mechanisms have been explored, and the results show that ovarian hormones play a critical role in modulating the reinforcing effects of drugs of abuse in females. Preclinical studies, in conjunction with human studies, should further inform a sex-specific model for differences in drug abuse, and such a model may be useful for developing prevention and treatment strategies for drug abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in preferences to photographs.

Individual differences in preferences to photographs were explored based on an alternative framework. This framework predicts that the primary difference between individuals in this respect is their ability to process photographic information, which in turn influences their preferences. Chiefly, people with well-developed schemes in photography (e.g., photo professionals) should have a higher ability to process photographic information than people with less developed schemes (e.g., psychology students). Consequently, people with well-developed schemes in photography should prefer photographs that are relatively more demanding to process. Ten psychology students and 5 photo professionals assessed 32 photographs on six general concepts: Preference, Hedonic Tone, Expressiveness, Familiarity, Uncertainty, and Dynamics. As predicted, photo professionals had a higher ability to process photographic information and preferred photographs that were relatively uncertain and unfamiliar. These results are in concordance with previous research and give strong support to the utility of the present framework in experimental aesthetics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-motivational effects of inescapable shock are associative in nature.

An appetitive choice discrimination test was used to assess the relative contribution of activity and associative effects of inescapable shock (IS) in a cross-motivational paradigm. A 2-response nosepoke test was used following IS treatment. In Exp I, male Holtzman rats demonstrated separate associative and activity effects of IS. Ss exposed to IS made more incorrect responses than controls and were lower in activity. Exp II demonstrated that these effects resulted from the uncontrollability of the shock, not from shock exposure per se. In Exp III, residual effects of IS were investigated by exposing Ss to discrimination reversals. On these tests, shocked Ss showed performance inferior to nonshocked controls, a result indicating that the effects of IS were not completely reversed by experience with contingent reward in the discrimination task. Results suggest that associative factors play a more important role than activity reduction in mediating the effects of IS, at least when these are measured in an appetitive context. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ventromedial septal lesions in rats reduce the effects of inescapable shock on escape performance and analgesia.

In 2 experiments with 104 male Sprague-Dawley rats, lesions of the ventromedial septum (VMS) reduced or eliminated several effects of exposure to inescapable shock, but lesions of the dorsolateral septum did not. Exp I demonstrated that VMS lesions reduced the loss in body weight produced by inescapable shock and eliminated the subsequent (24 hrs later) interference with escape performance (learned helplessness). Exp II demonstrated that VMS lesions reduced the analgesia that occurs immediately following inescapable shock and the analgesia reinstated by exposure to escapable shock 24 hrs later. Findings indicate that VMS lesions reduce several responses to inescapable shock and suggest the possibility that all of these effects may reflect a unitary deficit. It is hypothesized that VMS lesions reduce these effects of exposure to inescapable shock either by reducing the ability of the rats to learn that their responses and shocks were uncorrelated or by reducing the emotional impact of this lack of correlation. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in susceptibility to inattentional blindness.

Inattentional blindness refers to the finding that people do not always see what appears in their gaze. Though inattentional blindness affects large percentages of people, it is unclear if there are individual differences in susceptibility. The present study addressed whether individual differences in attentional control, as reflected by variability in working memory capacity, modulate susceptibility to inattentional blindness. Participants watched a classic inattentional blindness video (Simons & Chabris, 1999) and were instructed to count passes among basketball players, wherein 58% noticed the unexpected: a person wearing a gorilla suit. When participants were accurate with their pass counts, individuals with higher working memory capacity were more likely to report seeing the gorilla (67%) than those with lesser working memory capacity (36%). These results suggest that variability in attentional control is a potential mechanism underlying the apparent modulation of inattentional blindness across individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Individual differences in reaction to failure-induced stress.

"The McKinney Reporting Test and the MMPI were administered to samples of aviation cadets, aircraft commanders, copilots, and ROTC student officers. Two criterion groups representing the extremes in adjustment were selected within each of the military samples… . There was an overall-significant tendency among the low adjustment cases for those who shifted toward more accurate performance on the McKinney stress period to answer on the Hy scale… like Janet's psychasthenic type, and for those who became more inaccurate to answer like the hysteric. This tendency did not hold for high adjustment cases." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences and cues to deception.

In an extension of previous studies on deception and deception detection, the present study investigated the relations among individual differences, behavioral cues displayed when deceiving and telling the truth, and the perceptions of naive observers. 63 undergraduates were measured on the Self-Monitoring Scale, the Affective Communication Test, the Personality Research Form, the Eysenck Personality Inventory, their acting ability, and their overall appearance. They were then videotaped while deceiving and while telling the truth, and their verbal and nonverbal cues were rated and coded. Their success at creating an honest appearance was assessed by showing edited videotapes of their faces or their bodies to naive judges (176 undergraduates), with and without sound. Behavioral cues validly discriminated truthfulness from deception, but these valid cues were not necessarily used or were incorrectly used by the judges. Comparison of the facial and body conditions suggested explanations for the relative inaccuracy of face-viewing judges. Individual differences were related to the overall display of behavioral cues, to variance in the display of cues from deceptive to truthful conditions, to overall perceptions of truthfulness, and to successful deception. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress and adenosine: II. Adenosine analogs mimic the effect of inescapable shock on shuttle-escape performance in rats.

Examined, in 3 experiments involving 208 male rats, the role of adenosine regulation in escape deficits produced by earlier exposure to inescapable shock in rats (learned helplessness). Adenosine analogs injected before escape testing mimicked the effect of earlier inescapable shock, with the magnitude of the deficit varying with dose and drug specificity for A? adenosine receptors. Agonist-induced and stress-induced escape deficits were eliminated by pretest treatment with the centrally acting adenosine receptor antagonist theophylline but not the peripheral antagonist 8-[p-sulfophenyl]-theophylline. Finally, preexposure to an ineffective number of inescapable shocks interacted in synergy with an ineffective pretest injection of adenosine agonist to maximize deficits in escape performance. These data implicate energy regulation and a central compensatory action by adenosine in the aspects of helplessness related to onservation–withdrawal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to inescapable stress persistently facilitates associative and nonassociative learning in rats.

The present study examined the proactive effects of inescapable stress on aversive Pavlovian conditioning. Stressed rats were restrained and exposed to 90 1-mA tailshocks. Twenty-four hours later, all rats were exposed to 10 conditioned stimuli (CS; 350 ms of white noise at 85 dB). Rats then received either paired training in which the CS coterminated with a 100-ms, 0.7-mA periorbital shock or the same stimuli presented in an explicitly unpaired fashion. After the unpaired exposures, these rats were also exposed to paired training. Previously stressed rats exhibited persistent sensitization to the white-noise stimulus. Stressed rats exposed to unpaired stimuli, and no longer exhibiting a sensitized response, acquired the eyeblink conditioned response at a facilitated rate when these stimuli were presented in a paired fashion. These results also demonstrate that the effect of stress on classical conditioning is long-lasting, in excess of 48 hr. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences and reactions to job characteristics.

Evaluated 3 different methods of measuring individual differences as moderators of employee reactions to job characteristics. The 3 methods are urban vs rural background, strong vs weak belief in the Protestant work ethic, and high vs low strength for "higher order" needs. Each of these 3 methods was used as a moderator of the relationships between job characteristics on the one hand, and specific job facet satisfaction, overall job satisfaction, and job behavior on the other hand. Data were obtained from 80 newly hired female telephone operators. Based on the job satisfaction results, higher order need strength was the most useful way to measure this type of individual difference, followed by the Protestant work ethic, and lastly by urban vs rural background of the worker. There were no differences among the 3 individual differences as moderators of the job characteristics and job behavior relationship. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in student cheating.

The incidence and causes of cheating were investigated using a questionnaire, consisting of 21 cheating behaviors, which was distributed to students at an English university. Respondents were asked to indicate, confidentially, which of the behaviors they had engaged in. Reported cheating was widespread and some types of cheating (e.g., on coursework) were more common than others. Reported cheating was more common in men than women; more common with less able students than more able ones; more common in younger students than mature ones; and more common in science and technology students than those in other disciplines. It is suggested that students' motivation, in particular whether they are studying to learn rather than simply to obtain good grades, is a major factor in explaining these differences. The results also indicate that cheating consists of a number of different types of behavior rather than being a unitary concept. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in cognitive processes.

Studied the effects of verbal ability and sex on performance in a simultaneous matching task. The 537 undergraduates who participated were administered the verbal battery of the Lorge-Thorndike Intelligence Test. Ss with high-verbal ability (high verbals) were much faster than Ss with low-verbal ability (low verbals) in making taxonomic category identity matches and homophone identity matches. Results suggest that verbal ability is related to the speed of retrieval from long-term memory. In addition, high verbals were faster in making physical identity word matches, suggesting that either lexicographically coded information stored in long-term memory is used in such a task or that verbal ability is also related to the speed of retrieval from short-term memory. As expected, males did not differ from females in the time they required to perform any of the matching tasks, although males made slightly more errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in causal uncertainty.

Presents a scale that measures chronic individual differences in people's uncertainty about their ability to understand and detect cause-and-effect relationships in the social world: the Causal Uncertainty Scale (CUS). The results of Study 1 indicated that the scale has good internal and adequate test–retest reliability. Additionally, the results of a factor analysis suggested that the scale appears to be tapping a single construct. Study 2 examined the convergent and discriminant validity of the scale, and Studies 3 and 4 examined the predictive and incremental validity of the scale. The importance of the CUS to work on depressives' social information processing and for basic research and theory on human social judgment processes is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in dream recall.

Ss who typically fail to remember dreams at home (nonreporters) and Ss who frequently remember dreams (reporters) slept in the laboratory for 4 nights each. Gradual or abrupt awakenings were made at each EEG Stage-I REM (dream) period. Although nonreporters and reporters did not differ in REM-period frequency or EEG patterns during sleep, nonreporters did report dreaming less frequently following REM-period awakenings. Ss showed self-consistency in frequency of dream reporting and in type of failure to report. Some nonreporters typically failed to remember any content; others typically said they were awake and thinking. Comparisons among reporters and sub-groups of nonreporters for eye-movement frequency, arousal threshold, and dreamlike-report content indicate that it may be useful to distinguish different kinds of nonreporters. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)