Immediate and proactive effects of controllability and predictability on plasma cortisol responses to shocks in dogs.

18 adult male dogs were exposed to 3 treatments: habituation to a hammock, stress induction, and a shuttlebox test. At each stage, blood samples were drawn and plasma cortisol was assayed. In the initial stress-induction phase, the controllability and predictability of electric shocks were independently varied. In a subsequent test phase, all groups received identical shocks in a novel situation. Cortisol responses to these test shocks were analyzed as a function of the controllability and predictability of previous induction shocks. Results show that during stress induction, uncontrollable shocks produced significantly greater cortisol elevations than controllable shocks, but predictability had no significant effect on cortisol responses. However, unpredictable shocks during stress induction acted proactively to significantly increase cortisol responses to novel test shocks, whereas prior controllability did not modulate subsequent responsivity to novel shocks. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

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)     

Panic-relevant predictability preferences: A laboratory test.

In the present investigation the authors evaluated the role of verbally instructed safety periods as they relate to predictability preference within a single-session challenge paradigm involving recurrent administrations of 20% carbon dioxide (CO?) enriched air. Participants included 160 nonclinical young adults (91 women, 69 men) between the ages of 18 and 59 (M=21.6 years; SD=7.23). Results indicated that equivalent levels of anxiety were experienced during predictable and unpredictable administrations of 20% CO?, yet participants preferred predictable compared with unpredictable trials, with women showing a stronger predictability preference than men. Lower anxiety was reported during known safety periods (predictable room air trials) but not during predictable compared with unpredictable administrations of 20% CO?. Findings are discussed in relation to theoretical and applied implications for the role of predictability in the nature of anxiety and its disorders. (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)     

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)     

Effects of temporal predictability on the reactions of 1-year-olds to potentially frightening toys.

Three experiments examined the effects of temporal predictability on 227 1-yr-old infants' reactions to potentially frightening, mechanical toys. Ss responded less fearfully to toys that played on predictable as compared to unpredictable schedules. Being able to predict how long the toys would stay off each time they stopped playing, rather than how long they would play once they came on, was the aspect of the predictable schedules that reduced fear. Fixing the duration of these intertrial intervals did not reduce fearful behavior by increasing the predictability of when the toys would start playing. In fact, signaling each activation increased negative reactions. Neither uncertainty-based hypotheses nor preparatory-response hypotheses can account for these data. Data most closely approximate M. Seligman's (1975) safety-signal model. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suppression of licking behavior in rats as a function of predictability of shock and probability of conditioned-stimulus-shock pairings.

In Exp I, the effects of various degrees of predictability of electric shock upon rats' licking behavior were studied using 45 male albino rats. The basal rate of licking became progressively lower as unpredictability of shock increased. It was also found that Ss could utilize "time" as a predictor of safety and danger. In Exp II, using 48 Ss, the relationship between conditioned emotional response (CER) and the probability of conditional stimulus (CS) being paired with shock was studied under the matched basal rate of licking by making all shocks predictable. The CER was an increasing function of the probability of CS-shock pairings. Results are discussed with reference to M. Seligman's (1969) safety-signal hypothesis and R. Rescorla's (1968) probabilistic theory. (19 ref) (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)     

Sex differences in effects of predictable and unpredictable footshock on fentanyl self-administration in rats.

An operant conditioning paradigm was used to examine effects of predictable and unpredictable footshock on oral fentanyl (50 μg/ml) self-administration (SA) in 12 female and 12 male Wistar rats (Rattus norvegicus). Rats were tested for drug SA under a progressive ratio schedule with and without repeated predictable or unpredictable footshock over 8 weeks. Female rats consumed greater amounts of fentanyl than did male rats. Male rats exhibited greater withdrawal behaviors following naloxone challenge. Predictable footshock with repeated exposure (i.e., chronic stress) was accompanied by greater fentanyl SA than was unpredictable footshock, particularly for female rats. Corticosterone levels were positively correlated with fentanyl SA. Predictability of the stressor also had a greater effect on maintenance of fentanyl SA than it did on relapse to fentanyl SA. Results suggest that sex plays an important role in drug-taking behavior by rats. (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)     

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)     

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)     

Possible amotivational effects following marijuana smoking under laboratory conditions.

Human participants earned money by responding on a progressive-ratio (PR) schedule (initial value $50) or received money without responding on a fixed-time (FT) schedule. During the session, participants could terminate the PR schedule and initiate an FT 200-s schedule. In Experiment 1, increases in monetary value produced increased number of responses, time spent, and money earned in the PR component. In Experiment 2, marijuana smoking produced potency-related reductions in the number of responses, time spent, and money earned in the PR component, effects that can be interpreted as amotivational. Increasing the monetary value of the reinforcer diminished the acute marijuana effects on PR responding, suggesting that marijuana exerted an effect primarily on reinforcers of a smaller magnitude. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predictable and unpredictable rewards produce similar changes in dopamine tone.

Unpredicted rewards trigger more vigorous phasic responses in midbrain dopamine (DA) neurons than predicted rewards. However, recent evidence suggests that reward predictability may fail to influence DA signaling over longer scales: In rats passively receiving rewarding electrical brain stimulation, the concentration of DA in dialysate obtained from nucleus accumbens probes was similar regardless of whether reward onset was predictable (G. Hernandez et al., 2006). The present experiment followed up on these findings by requiring the rats to work for the rewarding stimulation, thus confirming whether they indeed learned the timing and predictability of reward delivery. Performance under fixed-interval and variable-interval schedules was compared, and DA levels in the nucleus accumbens were measured by means of in vivo microdialysis. The observed patterns of operant responding indicate that the rats working under the fixed-interval schedule learned to predict the time of reward availability, whereas the rats working under the variable-interval schedule did not. Nonetheless, indistinguishable changes in DA concentration were observed in the 2 groups. Thus, reward predictability had no discernable effect on a measure believed to track the slower components of DA signaling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Specific phosphatidylethanolamine dependence of Serratia marcescens cytotoxin activity

A region of dorsomedial frontal cortex (DMFC) has been implicated in planning and executing saccadic eye movements; hence it has been referred to as a supplementary eye field (SEF). Recently, activity related to executing smooth-pursuit eye movements has been recorded from the DMFC, and microstimulation here has been shown to evoke smooth eye movements. This report documents neuronal activity present in smooth-pursuit tasks where the predictability of target motion was manipulated. The activity of many neurons in the DMFC reached a peak when a predictable change in target motion occurred. Furthermore, the peak activity of some cells was systematically shifted by manipulating the duration of the target event, indicating that the network these neurons were in could learn the temporal characteristics of new target motion. Finally, the activity of most neurons tested was greater when target motion was predictable than when it was unpredictable. The results suggest that the DMFC participates in planning smooth-pursuit eye movements based on past stimulus history.     

Eye movements and word skipping during reading: Effects of word length and predictability.

Eye movements were monitored as subjects read sentences containing high- or low-predictable target words. The extent to which target words were predictable from prior context was varied: Half of the target words were predictable, and the other half were unpredictable. In addition, the length of the target word varied: The target words were short (4–6 letters), medium (7–9 letters), or long (10–12 letters). Length and predictability both yielded strong effects on the probability of skipping the target words and on the amount of time readers fixated the target words (when they were not skipped). However, there was no interaction in any of the measures examined for either skipping or fixation time. The results demonstrate that word predictability (due to contextual constraint) and word length have strong and independent influences on word skipping and fixation durations. Furthermore, because the long words extended beyond the word identification span, the data indicate that skipping can occur on the basis of partial information in relation to word identity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

New developments in the role of cytokines and chemokines in inflammatory myopathies

Humans are readily able to distinguish expected and unexpected sensory events. Whether a single mechanism underlies this ability is unknown. The most common type of expected sensory events are those generated as a consequence of self-generated actions. Using H2 15O PET, we studied brain responses to such predictable sensory events (tones) and to similar unpredictable events and especially how the processing of predictable sensory events is modified by the context of a causative self-generated action. Increases in activity when the tones were unpredictable were seen in the inferior and superior temporal lobe bilaterally, the right parahippocampal gyrus and right parietal cortex. Self-generated actions produced activity in a number of motor and premotor areas, including dorsolateral prefrontal cortex. We observed an interaction between the predictability of stimuli and self-generated actions in several areas, including the medial posterior cingulate cortex, left insula, dorsomedial thalamus, superior colliculus and right inferior temporal cortex. This modulation of activity associated with stimulus predictability in the context of self-generated actions implies that these areas may be involved in self-monitoring processes. Detection of expected stimuli and the detection of the sensory consequences of self-generated actions appear to be functionally distinct processes, and are carried out in different cortical areas. These observations support theoretical approaches to cognition that postulate the existence of a self-monitoring system.     

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)     

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)