The psychological difference between temporally predictable and unpredictable stressful events: Evidence for information control theories.

80 18–40 yr old female volunteers participated in an experiment in which temporal information about the onset of an aversive stimulus (shock) was varied to test the hypothesis, implied by information control theories, that predictable aversive events are more beneficial than unpredictable ones. Each S acted as her own control and received 6 predictable and 6 unpredictable shock trials. Findings support information control views. Ss reported to have felt less distress during the interval before the predictable shocks, they perceived the predictable shocks to be less aversive than the unpredictable ones, and autonomic indexes of arousal were lower during the signal for the predictable condition than during the equivalent periods for the unpredictable condition. 64% of the Ss preferred the predictable condition. There were no individual differences in personality or anxiety dimensions, as measured by the Eysenck Personality Questionnaire and the Trait scale of the State-Trait Anxiety Inventory, that could account for these preferences. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Greater sustained anxiety but not phasic fear in women compared to men.

Startle reflex studies in rodents indicate that female are more reactive than rats in experimental models of sustained anxiety but not in models of phasic fear (Toufexis, 2007). This study examined evidence for a similar effect in humans. Participants were exposed to three conditions, (1) predictable aversive shocks signaled by a cue, (2) unpredictable shocks, and (3) no shocks. Acoustic startle stimuli were delivered regularly across conditions. Phasic startle potential to the threat cue in the predictable condition was not affected by sex. In contrast, and consistent with basic research, the sustained increase in startle in the predictable and unpredictable conditions was greater in women compared to men. Animal studies suggest that such an effect may be mediated by the effects of sexual dimorphism in limbic structures, including the bed nucleus of the stria terminalis. However, psychosocial factors may also contribute to this effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choosing between predictable and unpredictable shock conditions: Data and theory.

Reviews the literature on predictability and describes the factors that affect choice. Emphasis is given to the reliability of basic findings, including replications and failures to replicate. Behavioral measures related to choice are reviewed, and some physiological correlates of predictable and unpredictable shock are noted. The data allow several firm conclusions regarding preference, notably that (a) rats (albino, hooded, male, female) prefer predictable shock conditions; (b) they prefer predictable conditions whether shock is avoidable, escapable, or inescapable and whether it is scrambled or unscrambled grid shock; (c) this preference occurs with different procedures, apparatus, and shock delivery systems, such as water electrodes or electrodes attached to the tail, back, ears, or pubis bone; (d) fish and birds also prefer the signaled condition; and (e) although the preference is robust, it is affected by shock intensity, signal duration, intershock intervals, amount of training, and the dependability of shock-free periods. Other factors that may affect preference are also noted. Finally, the theoretical views of conditioned reinforcement, of information, of preparation, and of safety are evaluated, and their strengths and weaknesses are described (4 p ref) (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)     

Alcohol selectively reduces anxiety but not fear: Startle response during unpredictable versus predictable threat.

Recent theory and empirical research have suggested that fear and anxiety are distinct processes with separable neurobiological substrates. Furthermore, a laboratory procedure has been developed to manipulate fear versus anxiety independently via administration of predictable or unpredictable electric shock, respectively. Benzodiazepines appear to selectively reduce anxiety but not fear in this procedure. The primary aim of this experiment was to determine if alcohol produced a similar selective reduction in anxiety. Intoxicated (target blood alcohol concentration of .08%) and nonintoxicated participants viewed a series of colored squares separated by variable intertrial intervals (ITIs) in 3 conditions. In the predictable shock condition, shocks were administered contingently during every square. In the unpredictable shock condition, shocks were administered noncontingently during both squares and ITIs. In the no-shock condition, no shocks were administered at any time. Alcohol significantly reduced startle potentiation during cues signaling unpredictable but not predictable shock, consistent with the thesis that alcohol selectively reduces anxiety but not fear. In addition, alcohol’s effect on startle potentiation during unpredictable shock was mediated by vigilance. This anxiolytic effect may clarify the nature of alcohol’s reinforcing effects in social and problem drinkers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mental illness, predictability, and affective consequences as stimulus factors in person perception.

Before and after attempting to predict the behavior of a stimulus person (SP) in a choice situation, 64 Ss were asked to record their impressions of him on a trait rating scale. By design (a) the SP was presented as normal or mentally ill, (b) his behavior was predictable or unpredictable, and (c) errors of prediction were or were not signaled by a noxious buzzer. As predicted, evaluative judgments of the mentally ill SP did not vary as a function of predictability unless predictive failures were accompanied by unpleasant consequences, and unless the SP himself had control over the delivery of these consequences. Judgments of the normal SP were solely a function of his predictability, regardless of the consequences of predictive failure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ingestion of environmentally contaminated Lake Ontario salmon by laboratory rats increases avoidance of unpredictable aversive nonreward and mild electric shock.

To determine what behavioral changes are caused by consumption of Lake Ontario salmon, a 30% diet of Lake Ontario or control Pacific Ocean salmon was fed to rats for 20 days. In Experiments 1 and 2 (preference-for-predictability E-maze test), rats fed Lake Ontario salmon developed a preference for predictable food rewards more quickly than did the control rats. In Experiments 3 (passive avoidance) and 4 (conditioned suppression), rats fed Lake Ontario salmon suppressed responding to food far more after the introduction of mild electric shocks than did control rats. All results supported the hypothesis that ingestion of Lake Ontario salmon, contaminated with polychlorinated biphenyls, mercury, lead, etc., increases the reactivity of rats to aversive events. The results were successfully simulated by DMOD, a mathematical model of learning, using the assumption that rats fed Lake Ontario salmon find unpredictable nonreward and mild shock more aversive. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for a putative biomarker for substance dependence.

Electrodermal response modulation (ERM) reflects the reduction in skin conductance response to an aversive stimulus that is temporally predictable relative to when it is unpredictable. Poor ERM is associated with substance dependence (SD). It was hypothesized that ERM is a putative biomarker for SD rather than for externalizing disorders generally. Participants included 83 controls (no SD, antisocial personality disorder [PD] or borderline PD), 52 participants with SD only (SD and no PD), 12 with PD only (antisocial and/or borderline PD and no SD), and 35 comorbid (having SD and PD). Diagnoses at definite and probable certainty levels were used and were determined by semistructured clinical interviews. ERM was calculated from skin conductance responses to predictable and unpredictable 2-s 110-dB white noise blasts. As expected, the SD-only and comorbid groups had significantly lower ERM scores than the control group, which did not differ significantly from the PD-only group. Results provide preliminary evidence that ERM is a putative biomarker for SD. Future research should examine cognitive correlates of ERM in an effort to understand why it relates to SD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predictable and unpredictable shock: Behavioral measures of aversion and physiological measures of stress.

Reviews the literature on predictable and unpredictable shock conditions relative to physiological measures of stressfulness and considers the possible role of stress-induced analgesia in both physiological and behavioral effects. Findings suggest that unpredictable conditions are physiologically more stressful than predictable conditions when Ss are exposed to them for one or a few sessions and when parameters of stress are relatively severe. However, predictable conditions may be more stressful than unpredictable conditions when sessions are long and extend over days and when parameters of stress are less severe. The effect of extended stress appears to depend on the physiological measure used. These findings are discussed in terms of the phasic vs chronic nature of predictable vs unpredictable stress and the organism's ability to adapt physiologically to these conditions. Data on stress-induced analgesia are also reviewed. It is concluded that stress-induced analgesia does not significantly contribute to either preference for predictable over unpredictable stress or to their differential physiological effects. (88 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensation Seeking and the Aversive Motivational System.

Sensation seeking (SS) has traditionally been viewed as a phenomenon of the appetitive motivational system. The limited SS research exploring contributions from the aversive motivational system reveals greater anxious reactivity to dangerous activities among low sensation seekers. The present study extends this line of work by comparing levels of fear and anxiety during anticipation of predictable and unpredictable aversive stimuli across high- and low-SS groups. Low sensation seekers displayed greater fear-potentiated startle (FPS) to predictable aversive stimuli, and only those low on SS showed FPS and skin conductance response effects during experimental contexts in which aversive stimuli were delivered unpredictably. Findings implicate enhanced apprehensive anticipation among those low on SS as a potential deterrent for their participation in intense and threatening stimulus events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reported physical symptoms elicited by unpredictable events and the Type A coronary-prone behavior pattern.

Hypothesized that unpredictable aversive events are causally linked to physical symptom reporting and that the Type A coronary-prone behavior pattern affects symptom reporting, such that Type A individuals fail to report symptoms when they expect to continue working on a task as compared to when they believe they have completed it. In the present study, 120 Type A and Type B female undergraduates (classified by scores on the Jenkins Activity Survey for Health Prediction) reported symptoms either at the end or in the middle of listening to unpredictable, predictable, or ambient noise in the laboratory. Unpredictable noise produced more symptom reporting than predictable noise, which in turn produced more symptom reporting than the ambient noise; Type A Ss reported fewer symptoms in the middle of the task than at the end, whereas Type Bs did not. Thus, both hypotheses were confirmed. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired relational equivalence: Implications for the nature of associative structures.

In 2 experiments, rats received discrimination training in which separate presentations of A and B signaled a common pair of relationships or associations (X?→?food and Y?→?no food), whereas presentations of C and D signaled a different pair of relationships (X?→?no food and Y?→?food). To assess the nature of the associative structures acquired during this training, rats then received 2 types of revaluation procedure: In Experiment 1, A was paired with shock and C was not. In Experiment 2, the relationships that A and B had previously signaled (X?→?food and Y?→?no food) were paired with shock, whereas those that C and D had signaled (Y?→?food and X?→?no food) were not. After both types of revaluation treatment, rats showed greater generalized conditioned suppression in the presence of B than D. These results indicate that A, B, C, and D come to evoke memories of the relationships or associations that they have signaled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential gastric ulceration in rats receiving shocks on either fixed-time or variable-time schedules.

Research suggests that predictable electric shocks produce less stress than unpredictable shocks. In this experiment, predictability was manipulated by using fixed-time (FT, predictable) and variable-time (VT, unpredictable) schedules of shock delivery. Rats receiving 3-mA, 1-s electric shocks on a FT 45-s schedule developed less gastric pathology than another group that was administered identical shocks on a VT 45-s schedule. It is argued that this finding represents a more subtle effect of predictability than has been obtained heretofore. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preference for unpredictable food rewards occurs with high proportion of reinforced trials or alcohol if rewards are not delayed.

A recently developed mathematical model (DMOD) also predicts that Ss prefer the unpredictable reward situation under conditions that substantially decrease aversiveness of unpredictable nonreward (Daly & Daly, 1982). Because a high proportion of reinforced trials (lenient schedule) and alcohol decrease aversive conditioning, these variables were tested with rats in 5 E-maze experiments. A choice to 1 side of the maze resulted in a stimulus uncorrelated with reward outcome (unpredictable). A choice to the other side resulted in stimuli correlated with reward and nonreward (predictable). Stimuli were not visible until after the choice was made. A lenient reinforcement schedule resulted in preference for the unpredictable reward situation if rewards were not delayed. Alcohol resulted in preference for the unpredictable reward situation if a medium 5-pellet reward was given. A lenient reinforcement schedule combined with an alcohol injection resulted in faster acquisition of the preference for the unpredictable reward situation than did a lenient schedule combined with a saline control injection. These results pose a major challenge to most theories, yet were predicted by DMOD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress of predictable and unpredictable shock.

Examined the claim that unpredictable shock is more stressful than predictable shock in short-term studies (B. B. Abbott et al; see record 1984-28077-001). The classification of studies as short- or long-term, the conceptualization of predictability studies, and the failure to note contrary evidence are discussed. It is concluded that predictable shock (the presence of a warning signal before shock) makes the situation more stressful both in short- and long-term studies. It is suggested that conflicting results are probably due to the presence of additional and confounding variables in contrary studies. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An aversive treatment for addicted cigarette smokers: Preliminary report.

An aversive stimulus (electric shock) was paired with cigarette smoking in two groups of addicted smokers. In one group (E) the shock was made increasingly painful, in the other group (C) it was subliminal. In both groups shock was terminated when S put out his cigarette. Treatment was given in one session, with an average of 10 smoking-shock pairings per S. On 25% of trials shock was omitted. The treatment greatly reduced smoking in group E (9 Ss) but not in group C (4 Ss), and therefore has promise for the treatment of heavy smokers. Some subsidiary effects of the treatment were also noticed. More than two years after treatment there was evidence of reduced rates in some E group subjects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Morphine promotes autonomic learning.

Morphine (0.01-10 mg/kg) promoted rapid autonomic learning of discriminative, Pavlovian conditioned heart rate decelerations to tone signals in male and female rabbits, and the higher doses (1-10 mg/kg) promoted decelerative heart rate orienting reflexes to novel tones. Morphine does dependently reduced heart rate acceleration to signaled shock but had no effect on heart rate acceleration to unsignaled shock. Morphine did not impair retention of cardiac conditioned reflexes, and its U-shaped dose effect, increasing conditioned heart rate discrimination early in training, reappeared in extinction. The authors propose that morphine promotes autonomic learning of preparatory, compensatory reflexes to signaled stressors that reduce their stressful effects. This action may mimic the normal, adaptive function of an endogenous messenger released by the Pavlovian contingency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immediate shock deficit in fear conditioning: Effects of shock manipulations.

Pavlovian contextual fear conditioning occurs when an aversive unconditional stimulus (US), such as a footshock, is presented to a rat shortly after it is placed in an experimental context. Contextual fear conditioning does not occur when the shock is presented immediately upon placement of the rat in the novel chamber. In the present study, the authors report that increasing either the number of immediate shock sessions (Experiment 1) or the immediate shock duration (Experiment 2) did not reverse this deficit. However, immediate shock seems to sensitize subsequent context conditioning (Experiment 3). These findings suggest that the associative deficit produced by immediate shock is not related to the rat's ability to process the footshock US. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention, unpredictability, and reports of physical symptoms: Eliminating the benefits of predictability.

Conducted 3 experiments with 135 undergraduates to investigate the established finding from the unpredictability literature that exposure to unpredictable noise leads to reports of more severe physical symptoms than does exposure to predictable noise. In Exp I, Ss performed a reaction time (RT) task while they listened to loud bursts of either predictable or unpredictable noise. As expected, RTs were slower when the noise was unpredictable than when it was not. This finding suggests that more attention had been directed to the unpredictable than the predictable noise. In Exp II and III, Ss were exposed to either predictable or unpredictable noise and were instructed to attend to the noise or were given no instructions. In both cases, Ss not instructed to attend to the noise reported more severe symptoms when the noise was unpredictable than when it was not, thus replicating the previous finding. Of greater interest, however, was the fact that equating the amount of attention directed to the unpredictable and predictable noise (by asking Ss to attend to the noise) eliminated the apparent benefits of predictability. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central and basolateral amygdala neurons crash the aversive conditioning party: Theoretical comment on Rorick-Kehn and Steinmetz (2005).

Rorick-Kehn and Steinmetz (2005) (see record 2005-13804-012) report that neurons in the central and basolateral nuclei of the amygdala exhibit learning-related spike firing to conditional stimuli associated with shock in 3 different aversive conditioning paradigms: eyeblink conditioning, fear conditioning, and signaled avoidance conditioning. Central nucleus neurons responded in all 3 tasks, whereas basolateral nucleus neurons were more activated by fear and avoidance conditioning. These results reveal that amygdala neurons are differentially engaged by aversive conditioning, but questions remain concerning the associative basis and functional role for these unit responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)