Conditioned inhibition and tonic immobility: Stimulus control of an innate fear response in the chicken.

Investigated the role of Pavlovian contingencies in modifying the tonic immobility reaction (IR) of Production Red chickens (N = 62) in 2 experiments. In Exp. I, Ss which received a stimulus associated with shock onset (CS1) showed facilitated duration of and increased susceptibility to IR compared with Ss which received a cue paired with shock offset (CS2). However, the lack of difference between Ss receiving CS1 and Ss receiving no stimulation, and the relatively low duration of IR, implied that CS2 training could mask the effects of conditioned fear. Exp. II provided an independent assessment of the relative strengths of CS1 and CS2. The former stimulus was shown to potentiate and the latter to actively inhibit IR. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intertrial interval effects in classically conditioned fear to a discrete conditioned stimulus and to situational cues.

In Exp I fear was classically conditioned in a total of 240 female hooded and Sprague-Dawley rats with a discrete conditioned stimulus (CS) at intertrial intervals (ITIs) of 15, 45, 75, 105, 165, or 225 sec and in Exp II, with an additional 144 Ss, with or without a discrete CS at ITIs of 165, 225, or 285 sec. The amount of fear conditioned to situational cues and to the discrete CS plus situational cues was then measured by the learning of a hurdle-jumping response which allowed escape from the fear-eliciting stimuli. Results suggest that as ITI was lengthened fear conditioned to situational cues alone and to the discrete CS increased. However, following conditioning with a discrete CS, fear elicited by situational cues increased with ITI but then decreased, presumably because a discrimination had been formed between the situational cues and the compound of CS plus situational cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tonic immobility in the blue crab (Callinectes sapidus, Rathbun): Its relation to threat of predation.

Investigated the tonic immobility response in the blue crab in a series of 7 experiments, using a total of 209 blue crabs. Although reported to be a powerful variable in other species, preinduction electric shock produced inconsistent increases in the duration of tonic immobility with the Ss. Manipulations that were more directly relevant to the fear of predation had considerably greater effects than shock. Physical damage to the chelipeds, mirror image stimulation, and immobilization beneath artificial glass eyes all produced significant prolongation of the immobility episode. Ss immobilized on a bed of sand rather than on a hard surface showed shorter immobility durations, suggesting that opportunity for escape is an important variable affecting the immobility reaction. Results support the contention that threat of predation is the organizing principle behind tonic immobility. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Latent inhibition experiments with goldfish (Carassius auratus).

Examined evidence of latent inhibition in a series of experiments with goldfish. In Exp I, 12 Ss were given nonreinforced preexposure to a color that subsequently predicted shock in an activity conditioning situation; their performance did not differ from that of 12 control Ss preexposed to a markedly different color. In Exp II, 12 Ss given nonreinforced preexposure to a tone and an unstimulated control group of 12 Ss were trained in an appetitive situation, with the tone serving either as a conditioned excitor or as a conditioned inhibitor. Preexposure had significant effect in the conditioned excitation training, but it reduced the level of responding both to the positive stimulus and to the negative compound in the conditioned inhibition training. In Exps III and IV, classical aversive conditioning was studied in the shuttle box. In Exp III, excitatory conditioning to a color was found to be impaired (relative to the performance of nonpreexposed control Ss) as much by nonreinforced preexposure to the training color as by nonreinforced preexposure to a markedly different color; substantial variation in amount of preexposure was without significant effect. In the conditioned inhibition training of Exp IV, 12 Ss with nonreinforced preexposure responded less than did 12 unstimulated control Ss, both to the positive stimulus and to the negative compound. Results demonstrate that the effect of preexposure on goldfish is their reduction of general responsiveness or level of arousal. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence of fear-reducing behavior: Relevance for the conditioning theory of neurosis.

Provided experimental support for O. H. Mowrer's (1939) conditioning theory of neurosis. 16 female naive hooded rats were given conditioned stimulus/stimuli (CS) shock trials (fear conditioning) in one side of a 2-compartment apparatus. Then, in the absence of shock, Ss were allowed to escape fear by jumping a hurdle to a safe compartment. The hurdle-jumping response was considered to be analogous to anxiety-based symptomatic behavior indicative of psychopathology in that the performance of the response was unrelated to the receipt of further shock. All Ss learned the hurdle-jumping response, and then performance gradually declined until an extinction criterion was reached. Thus, a response instrumental in reducing fear was learned and was maintained over many trials. A subsequent single fear-conditioning trial led immediately to a high level of performance followed by gradual extinction. Findings imply that, when fear is extinguished, instrumental responding can cease even though some response strength remains; the importance for therapy of focusing on the extinction of both instrumental (symptomatic) behavior and fear is suggested. Evidence for the spontaneous recovery of fear is also provided. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear conditioned with escapable and inescapable shock: Effects of a feedback stimulus.

Four experiments, with 140 male Fischer rats, compared the level of fear conditioned with escapable and inescapable shock. In Exps I and II, master Ss that had received 50 unsignaled escapable shocks were less afraid of the situation where the shock had occurred than were yoked Ss that had received inescapable shocks. Comparable results were found in Exps III and IV, which used freezing as an index of fear of a discrete CS that had been paired with shock. Control per se was not necessary to produce the low level of fear seen in the master Ss. Yoked groups receiving a feedback signal at the time the master made an escape response showed a low level of fear that was comparable to that of the masters and significantly less than that seen in the yoked Ss without feedback. In addition, there were strong suggestions that control and feedback exert their effects through the same or highly similar mechanisms. Possible explanations for how control and the exteroceptive feedback signal produce this effect are discussed. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus selection as a function of CS1-CS2 interval in compound classical conditioning of cats.

Investigated stimulus selection as a function of the time between the onsets of the longer and shorter elements of a compound stimulus (tone and light). The paw flexions and galvanic skin responses of 48 male and spayed female cats to shock were classically conditioned. With modality counterbalanced, each of 3 groups of Ss experienced a different CS1-CS2 interval: 2,000, 500, and 150 msec. The CS2 always preceded shock by 500 msec; all stimuli terminated together. After 8 wks of conditioning, Ss were tested to either the long or the short stimulus alone. Response strengths of the elements were clearly functions of the CS1-CS2 intervals, the shorter stimulus being more effective at the 2,000 and 150 msec intervals, the longer stimulus at the 500. Redundancy interpretation cannot account for all results. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear conditioning, meaning, and belongingness: A selective association analysis.

23 Ss rated the belongingness of pairs of conditionable (photographic slides) and unconditioned (e.g., shock, tone, human scream) stimuli. 40 new Ss were then classically conditioned, using rating-defined high (angry face/scream) and low (landscape/scream) belongingness pairs. Finger-pulse responses to the high-belongingness pairs showed superior acquisition and resistance to extinction. Another 40 Ss were conditioned to compound stimuli: a slide (either landscape or angry face) that was the same over trials, and a yellow or blue background that was the discriminant cue for the unconditioned stimulus (scream). When the angry face (the high-belongingness slide) was the invariant part of the compound, relatively poorer differential pulse-volume and skin-conductance conditioning was observed. Thus, depending on the task, a priori belongingness rendered stimuli selectively conditionable, either enhancing or inhibiting visceral response associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal-difference prediction errors and Pavlovian fear conditioning: Role of NMDA and opioid receptors.

Three experiments studied temporal-difference (TD) prediction errors during Pavlovian fear conditioning. In Stage I, rats received conditioned stimulus A (CSA) paired with shock. In Stage II, they received pairings of CSA and CSB with shock that blocked learning to CSB. In Stage III, a serial overlapping compound, CSB 3 CSA, was followed by shock. The change in intratrial durations supported fear learning to CSB but reduced fear of CSA, revealing the operation of TD prediction errors. N-methyl- D-aspartate (NMDA) receptor antagonism prior to Stage III prevented learning, whereas opioid receptor antagonism selectively affected predictive learning. These findings support a role for TD prediction errors in fear conditioning. They suggest that NMDA receptors contribute to fear learning by acting on the product of predictive error, whereas opioid receptors contribute to predictive error. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous configuring in conditioned flavor aversion.

Four experiments with 202 rats investigated spontaneous configuring, using the conditioned flavor-aversion paradigm. In Exp I, extended training of a 2-flavor compound stimulus did not produce spontaneous differentiation of conditioned responding to that compound and its elements. In Exp II, it was found that extended nonreinforced exposure to a compound stimulus generated spontaneous element–compound differentiation when the elements were later conditioned. Ss that received extended preexposure to the compound showed less conditioned responding to the compound than to either of its elements. However, Ss that had not received preexposure to the compound showed greater conditioned responding to the compound than to either of its elements (summation). In Exp III, nonreinforced preexposure to a compound stimulus prior to minimal reinforced compound training produced spontaneous compound–element differentiation, but extended reinforced compound training eliminated that differentiation. In Exp IV, extended partial reinforcement training with a compound produced differentiation of the compound from its elements. Implications of these data for the mechanisms responsible for spontaneous configuring, and for the summation assumptions common to most learning theories, are discussed. (38 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effect of administration of adrenalin on immobility reaction in domestic fowl.

Results of 2 experiments with White Leghorn chicks (N = 49) lend support to the hypothesis that tonic immobility is mediated by fear. In Exp. I, Ss injected subcutaneously with adrenalin remained immobile for a significantly greater duration than Ss injected subcutaneously with physiological saline. In Exp. II, it was found that a subcutaneous injection of adrenalin both facilitated the onset and maintained the duration of the immobility reaction in nonsusceptible Ss which previously showed no immobility. An injection of physiological saline neither facilitated nor maintained the immobility reaction in a control group of nonsusceptible Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus selection in eyelid conditioning in the rabbit (Oryctolagus cuniculus).

Conducted 2 experiments, using a total of 24 female New Zealand white rabbits, in which a "visual" stimulus (V), either flashes or electrical stimulation of the optic chiasma, was reinforced in compound with a differentially reinforced (CS+) or nonreinforced (CS–) nonvisual stimulus. Visual stimulus control of conditioned eyeblink activity was acquired if V was reinforced in compound with CS– but was "blocked" when reinforced in compound with CS+. Both effects were demonstrable within Ss and were independent of the method of visual stimulation. Extinction and backward conditioning of chiasmic stimulation preceded retraining of 6 Ss. The establishment and blocking of visual stimulus control were again evident within Ss. The data are interpretable in terms of either attentional or associative theory. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Pavlovian conditioned stimulus-unconditioned stimulus pairings during avoidance response-prevention trials in rats.

Response prevention (blocking) has been shown to hasten extinction of an instrumental avoidance response. One interpretation suggests that the facilitation effect is mediated by Pavlovian fear reduction during conditioned stimulus exposure on blocked trials. To test the fear-reduction hypothesis 30 male Holtzman albino rats received either a typical blocking treatment, blocking with shock, or extinction alone. Results indicate that blocking with the UCS was as effective as regular blocking in facilitating extinction of avoidance. An ancillary part of the experiment to assess the effectiveness of response prevention in 30 immature Ss showed that blocking did not facilitate extinction with the weanlings. Findings suggest that facilitated extinction is not solely attributable to Pavlovian fear reduction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian second-order conditioned analgesia.

Three experiments, with 118 Sprague-Dawley rats, assessed conditioned analgesia in a Pavlovian 2nd-order conditioning procedure by using inhibition of responding to thermal stimulation as an index of pain sensitivity. In Exp I, Ss receiving 2nd-order conditioning showed longer response latencies during a test of pain sensitivity in the presence of the 2nd-order conditioned stimulus (CS) than Ss receiving appropriate control procedures. Exp II found that extinction of the 1st-order CS had no effect on established 2nd-order conditioned analgesia. Exp III evaluated the effects of post 2nd-order conditioning pairings of subcutaneous morphine sulfate (10–20 mg/kg) and the shock unconditioned stimulus/stimuli (UCS). Ss receiving paired morphine–shock presentations showed significantly shorter response latencies during a hot-plate test of pain sensitivity in the presence of the 2nd-order CS than did Ss receiving various control procedures; 2nd-order analgesia was attenuated. Data extend the associative account of conditioned analgesia to 2nd-order conditioning situations and are discussed in terms of the mediation of both 1st- and 2nd-order analgesia by an association between the CS and a representation or expectancy of the UCS, which may directly activate endogenous pain inhibition systems. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shock-induced hyperalgesia: IV. Generality.

Brief-moderate shock (3, 0.75 s, 1.0 mA) has opposite effects on different measures of pain, inducing antinociception on the tail-flick test while lowering vocalization thresholds to shock and heat (hyperalgesia) and enhancing fear conditioned by a gridshock unconditioned stimulus (US). This study examined the generality of shock-induced hyperalgesia under a range of conditions and explored parallels to sensitized startle. Reduced vocalization thresholds to shock and antinociception emerged at a similar shock intensity. Severe shocks (3, 25 s, 1.0 mA or 3, 2 s, 3.0 mA) lowered vocalization threshold to shock but increased vocalization and motor thresholds to heat and undermined fear conditioned by a gridshock or a startling tone US. All shock schedules facilitated startle, but only brief-moderate shock inflated fear conditioning. The findings suggest that brief-moderate shock enhances the affective impact of aversive stimuli, whereas severe shocks attenuate pain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the automatic nature of phobic fear: Conditioned electrodermal responses to masked fear-relevant stimuli.

Normal Ss (n?=?64) were exposed either to pictures of snakes and spiders or to pictures of flowers and mushrooms in a differential conditioning paradigm in which one of the pictures signaled an electric shock. In a subsequent extinction series, these stimuli were presented backwardly masked by another stimulus for half of the Ss, whereas the other half received nonmasked extinction. In support of a hypothesis that suggests that nonconscious information-processing mechanisms are sufficient to activate responses to fear-relevant stimuli, differential skin conductance response to masked conditioning and control stimuli was obvious only for Ss conditioned to fear-relevant stimuli. These results were replicated in a 2nd experiment (n?=?32), which also demonstrated that the effect was unaffected by which visual half-field was used for stimulus presentation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of facial expressions on the classical conditioning of fear.

Previous research has demonstrated that particular facial expressions more readily acquire excitatory strength when paired with a congruent unconditioned stimulus than when paired with an incongruent outcome. The present study with a total of 36 undergraduates extends these findings on the excitatory inhibitory role of facial expressions by demonstrating that particular facial expressions (fear and happy), when paired with a neutral cue (tone), can influence conditioning to the neutral conditioned stimulus (CS). Ss who had a fear expression paired with the neutral CS responded more to the fear expression than to the neutral CS, whereas Ss who had a happy expression paired with the neutral CS responded more to the neutral cue than to the happy expression. These findings strongly support predictions from "overshadowing" or "blocking" models of classical conditioning. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned fear and postshock emotionality in vicious circle behavior of rats.

Gave 64 female hooded Long-Evans rats 15 shock-escape trials in a runway (1 trial/day), followed by 30 extinction trials. Half of the Ss received regular extinction treatment, while the others received a punishing shock if they ran. The Ss' level of activity (or freezing) before the trial was used as an index of conditioned fear. In acquisition, these shocked Ss were less active before the trial than 56 additional Ss receiving identical treatment, but without shock. During extinction, punished Ss both ran longer and showed less pretrial activity. This directly supports the vicious circle hypothesis that punishment for running maintains the fear motivating the running. When postshock emotionality was induced before a trial, it tended to suppress vicious circle behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Additional exposures to a compound of two preexposed stimuli deepen latent inhibition.

The present experiments studied the role of error correction mechanisms in the latent inhibition of conditioned fear responses by conditioned stimulus (CS) preexposure. They demonstrated that a preexposed CS subjected to additional exposures in compound with either another preexposed stimulus or a novel stimulus was more latently inhibited than a preexposed CS which received additional exposures in isolation. They also showed that a preexposed CS subjected to additional exposures in compound with another preexposed stimulus was more latently inhibited than a preexposed CS given additional exposures in compound with a novel stimulus. These results were discussed in terms of the Hall–Rodriguez (2010) model of latent inhibition. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Reinstatement of Conditioned Fear in Humans Is Context Dependent and Impaired in Amnesia.

A contextual reinstatement procedure was developed to assess the contributions of environmental cues and hippocampal function in the recovery of conditioned fear following extinction in humans. Experiment 1 showed context specificity in the recovery of extinguished skin conductance responses after presentations of an auditory unconditioned stimulus. Experiment 2 demonstrated that fear recovery did not generalize to an explicitly unpaired conditioned stimulus. Experiment 3 replicated the context dependency of fear recovery with a shock as an unconditioned stimulus. Two amnesic patients failed to recover fear responses following reinstatement in the same context, despite showing initial fear acquisition. These results extend the known functions of the human hippocampus and highlight the importance of environmental contexts in regulating the expression of latent fear associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)