Thinking about Arabs and Muslims makes Americans shoot faster: Effects of category accessibility on aggressive responses in a shooter paradigm

Is the same person perceived as more dangerous if the perceiver is induced to think about Arab and Muslim categories versus no category? Using the shooter paradigm, this study investigated the effects of the accessibility of ethnic (Arab) versus religious (Muslim) categories versus no category on spontaneous aggressive responses toward a target with an ambiguous appearance. Results demonstrated that shooting reactions toward armed targets were faster than non‐shooting reactions toward unarmed targets, especially if the target was a man. Despite these main effects, participants made faster decisions to shoot an ambiguous armed target if primed with the category Arab or Muslim (versus no category priming). The findings indicate that the mere priming of these social categories is sufficient to facilitate aggressive responses, even if the targets themselves are ambiguous. Copyright © 2012 John Wiley & Sons, Ltd.     

Fear Extinction to an Out-Group Face: The Role of Target Gender

ABSTRACT— Conditioning studies on humans and other primates show that fear responses acquired toward danger-relevant stimuli, such as snakes, resist extinction, whereas responses toward danger-irrelevant stimuli, such as birds, are more readily extinguished. Similar evolved biases may extend to human groups, as recent research demonstrates that a conditioned fear response to faces of persons of a social out-group resists extinction, whereas fear toward a social in-group is more readily extinguished. Here, we provide an important extension to previous work by demonstrating that this fear-extinction bias occurs solely when the exemplars are male. These results underscore the importance of considering how gender of the target stimulus affects psychological and physiological responses to out-group threat.     

Picking Up the Gauntlet: How Individuals Respond to Status Challenges

How do people respond to status challenges? We suggest that responses depend on the relative status and genders of challenger and target. These variables affect appraisals about the status challenge (operationally defined as an act of incivility) and likely outcomes of various responses, and those appraisals proximately determine responses. Studies 1 and 2 show that male gender and high status were associated with more aggressive responses, whereas female gender and low status were associated with more avoidant responses. Study 3 shows that men's and women's responses were not perfectly antithetical: Men showed the greatest resistance toward peers, which may reflect greater sensitivity to status contests among men. Perceived legitimacy of challengers' actions and consequences affect the status–gender–response relationships.     

Effect of telencephalon ablation on the reinforcing and eliciting properties of species-specific events in Betta splendens

In male Betta splendens, aggressive behavior is drastically attenuated following telencephalon ablation. Because instrumental training and Pavlovian conditioning experiments with intact fish have suggested that associative factors may play an important role in the performance of agonistic behaviors, the effect of ablation on instrumental learning and Pavlovian conditioning was studied. In Experiment 1, ablation had no effect on the learning of the instrumental tunnel-swimming response reinforced by mirror presentation (i.e., viewing a conspecific), although the mirror presentations in yoked-control groups elicited fewer responses in ablates than in normal and sham-operated control fish. Yoked controls further established that instrumental responding was maintained by the reinforcement contingency and was not merely the result of increased motor activity. Experiment 2 studied Pavlovian conditioning of the components of the agonistic display. Unconditioned fin erection, gill erection, and tail beating (i.e., unconditioned responses, URs) to the mirror US all were less frequent in ablates than in normals or shams. Of these, only gill cover erection showed evidence of true conditioning (i.e., conditioned responses; CRs) in which responses to the conditioned stimulus (CS) are due to the pairings of CS and US (unconditioned stimulus). However, ablates suffered no impairment of conditioned gill erections. Ablates performed fewer fin erections to the CS; however, fin erection responses were not due to CS-US pairings but were attributable to pseudoconditioning. These results are related to hypotheses postulating the involvement of learning mechanisms in ablation-produced deficits and normal aggressive behavior.     

Mousekilling,intermale fighting,and conditioned emotional response in rats

Several possible relationships between two forms of aggression in rats were studied. First, mouse killing and spontaneous intermale fighting were found to be correlated. Rats which attacked other rats were those most likely to kill mice. To determine whether aggressive and nonaggressive rats were also differentially responsive to other situations involving emotional arousal, but not aggression, mouse-killers and nonkillers were compared in a conditioned emotional response (CER) situation. Mouse-killers showed greater suppression to the conditioned stimulus (CS) and to the situational cues of the apparatus. Therefore, a common arousal mechanism may underlie a number of diverse agonistic responses. Nevertheless, extensive mouse-killing experience did not increase the tendency of rats to fight with either adult males or juvenile males.     

Pavlovian conditioned inhibition of fear during shuttlebox avoidance behavior

Three experiments explored the development and function of conditioned inhibition of fear during the acquisition and maintenance of shuttlebox avoidance behavior. The development of inhibition to an exteroceptive feedback stimulus was found to be a function of the number of successive avoidance responses to which the animal had been trained and of the duration of the intertrial interval, a parameter shown also to affect the rate of acquisition of avoidance learning. Master animals who learned the instrumental avoidance response, and yoked animals who did not, showed equivalent inhibitory fear conditioning in each experiment. The results of one experiment suggest that conditioned inhibition plays no important role in “protecting” fear conditioned to the discrete warning signal during avoidance maintenance. These data indicate that feedback stimuli develop their inhibitory properties by a Pavlovian process and that certain aspects of their function may, therefore, be readily understood within the framework of mediational two-process learning theory.     

Conditioned activity and the interaction of amphetamine experience with morphine's activity effects

This experiment assessed the transfer effect of Pavlovian conditioning with d-amphetamine sulfate (1 mg/kg) on morphine's activity effects. Prior experience with amphetamine resulted in higher levels of activity when challenged with morphine (10 and 20 mg/kg). This interactive effect of amphetamine, however, was present only in those animals who had experienced amphetamine paired with the activity test situation. Animals who had received equivalent doses of amphetamine unpaired with the testing environment did not differ from drug-naive control animals. Analysis of predrug activity levels revealed a conditioned activity response in paired animals compared to the controls. These findings suggest that the response interaction between drug conditioned responses and drug unconditioned responses is an important determinant of cross-drug effects between drugs of different pharmacological classes.     

Emotional catharsis and aggression revisited: heart rate reduction following aggressive responding

The authors tested two components of the catharsis theory of aggression: physiological tension reduction and aggressive drive reduction. On the basis of work in the stress-aggression literature, they also examined the moderating effect of impersonal stress exposure on cathartic reductions in heart rate following aggressive responding. Participants were instructed to administer nonaggressive (correct button) or aggressive (shock button) responses to a frustrating confederate in a laboratory aggression paradigm, and half the participants were exposed to an impersonal stressor (aversive air blasts) during the procedure. Heart rate was recorded before and after the participants administered the aggressive or nonaggressive response. Analyses revealed that participants exhibited reductions in heart rate following aggressive but not nonaggressive responding, but this was the case only for those not exposed to the impersonal stressor. Heart rate reductions during the experimental blocks actually predicted the most intense aggression in a subsequent block of trials. The results are considered in light of different theories of aggression by J. E. Hokanson (1974) and L. Berkowitz (1990) and have implications for interventions with anger-prone individuals.     

Associative morphine tolerance in the rat: examinations of compensatory responding and cross-tolerance with stress-induced analgesia

The results of three experiments designed to examine the processes subserving associative tolerance to morphine's analgesic effects, as assessed by the tail-flick test, are reported. The experiments indicated that associative tolerance in male Holtzman rats was not subserved by conditioned compensatory responses but was cross-tolerant with an apparently nonopioid form of stress-induced analgesia (SIA). Experiment 1 showed that rats tested for morphine analgesia in a distinctive context that had been paired previously with morphine injections (5 mg/kg) were more tolerant than animals that had had this context explicitly unpaired with a series of morphine injections or animals that were drug-naive. There was no evidence of a conditioned compensatory response of hyperalgesia in animals given a saline injection in the presence of environmental stimuli that had been previously paired with morphine, even under test conditions designed to minimize the possibility of floor effects that might have obscured the detection of drug-compensatory hyperalgesia. Experiment 2 demonstrated that the footshock procedures used for stress induction produced an SIA that was not attenuated by naloxone (10 mg/kg). Experiment 3 replicated the associative tolerance phenomenon of Experiment 1 and again failed to find evidence of conditioned compensatory responses. It was found that animals exposed to footshock in the context that had been associated with morphine administration developed significantly less SIA than control animals. The relevance of these findings for associative models of drug tolerance is discussed.     

Goal-tracking behavior in the pond snail, Lymnaea stagnalis

The occurrence of goal-tracking, an unconditioned stimulus (US)-directed autoshaping behavior, was studied in open-field tests with control and classically conditioned pond snails, Lymnaea stagnalis. In an appetitive classical conditioning paradigm with a tactile stimulus as conditioned stimulus (CS) and a localized food stimulus as US a conditioned feeding response built up in the experimental but not in the control animals. In the post-training open-field tests the experimental group alone showed an enhanced attraction toward the source of water current in the environment which previously signalled the arrival of the US but did not act as CS in the classical conditioning procedure. We suggest that this stimulus-directed goal-tracking behavior in Lymnaea is the result of a classical-operant interaction, described so far only in vertebrate animals, and that neurophysiological analysis of this behavior is possible in this snail.     

Autoshaping the pigeon's gape response: acquisition and topography as a function of reinforcer type and magnitude.

The pigeon's key-pecking response is experimentally dissociable into transport (head movement) and gape (jaw movement) components. During conditioning of the key-pecking response, both components come under the control of the conditioned stimulus. To study the acquisition of gape conditioned responses and to clarify the contribution of unconditioned stimulus (reinforcer) variables to the form of the response, gape and key-contact responses were recorded during an autoshaping procedure and reinforcer properties were systematically varied. One group of 8 pigeons was food deprived and subgroups of 2 birds each were exposed to four different pellet sizes as reinforcers, each reinforcer signaled by a keylight conditioned stimulus. A second group was water deprived and received water reinforcers paired with the conditioned stimulus. Water- or food-deprived control groups received appropriate water or food reinforcers that were randomly delivered with respect to the keylight stimulus. Acquisition of the conditioned gape response frequently preceded key-contact responses, and gape conditioned responses were generally elicited at higher rates than were key contacts. The form of the conditioned gape was similar to, but not identical with, the form of the unconditioned gape. The gape component is a critical topographical feature of the conditioned key peck, a sensitive measure of conditioning during autoshaping, and an important source of the observed similarities in the form of conditioned and consummatory responses.     

The expression of c-Fos and colocalisation of c-Fos and glucocorticoid receptors in brain structures of low and high anxiety rats subjected to extinction trials and re-learning of a conditioned fear response

We designed an animal model to examine the mechanisms of differences in individual responses to aversive stimuli. We used the rat freezing response in the context fear test as a discriminating variable: low responders (LR) were defined as rats with a duration of freezing response one standard error or more below the mean value, and high responders (HR) were defined as rats with a duration of freezing response one standard error or more above the mean value. We sought to determine the colocalisation of c-Fos and glucocorticoid receptors-immunoreactivity (GR-ir) in HR and LR rats subjected to conditioned fear training, two extinction sessions and re-learning of a conditioned fear. We found that HR animals showed a marked decrease in conditioned fear in the course of two extinction sessions (16 days) in comparison with the control and LR groups. The LR group exhibited higher activity in the cortical M2 and prelimbic areas (c-Fos) and had an increased number of cells co-expressing c-Fos and GR-ir in the M2 and medial orbital cortex after re-learning a contextual fear. HR rats showed increased expression of c-Fos, GR-ir and c-Fos/GR-ir colocalised neurons in the basolateral amygdala and enhanced c-Fos and GR-ir in the dentate gyrus (DG) in comparison with LR animals. Our data indicate that recovery of a context-related behaviour upon re-learning of contextual fear is accompanied in HR animals by a selective increase in c-Fos expression and GRs-ir in the DG area of the hippocampus.     

An aggression machine: IV. Concurrent and predictive validity over ten years

The subjects (60 boys) were drawn from the sample of a longitudinal study of social development to represent extremely aggressive, anxious, constructive, and submissive patterns of behaviour at the age of 8. A year later they were tested with an aggression machine (PAM). This allows variation of the intensity of both aggressive attack and defence in different stimulus conditions. The intensity of defensive aggression towards different attackers as well as the response style variables, latency, duration, and number of responses were correlated with observed and self-reported data at the ages of 8, 9, 14 and 19. The results showed that the intensity of aggression toward a same-sex peer had the highest validity. Opposite sex and authority figures as attackers called up other associations and motives, such as conflicts with the mother and anxiety. From the response style variables the highest validity was obtained for reaction time. This correlated with constructive behaviour.     

Neuronal unit activity in the abducens nucleus during classical conditioning of the nictitating membrane response in the rabbit (Oryctolagus cuniculus).

Neuronal unit activity was recorded from the abducens (6th nerve) nucleus, the "final common path," during classical conditioning of the nictitating membrane (NM) response in the rabbit, with the use of a tone conditioned stimulus, an air puff unconditioned stimulus (UCS), 250-msec interstimulus interval, and 60-sec intertrial interval. Animals were given 2 days of conditioning training (104 trials in eight blocks per day) and 1 day of extinction. Control animals were given comparable periods of stimulus presentations, explicitly unpaired. Activity of small clusters of units--"multiple unit" recording--was compared with the amplitude-time course of the NM response. Between-blocks comparisons of neural and behavioral responses indicated an essentially perfect correlation during acquisition of the conditioned response (Day 1, r = .99; Day 2, r = .98) and a slightly lower correlation during extinction (r = .93) for the conditioning animals. Within-blocks comparisons indicated a close correspondence between the histograms of unit activity and the amplitude-time course of the NM response for the conditioning animals in all phase of training and for the control animals in the UCS trial blocks.     

Heart rate changes accompanying jaw movement Pavlovian conditioning in rabbits: Concomitant blood pressure adjustments and effects of peripheral autonomic blockade

Two experiments were conducted to ascertain the cardiovascular accompaniments of differential Pavlovian jaw movement (JM) conditioning. The first examined the blood pressure (BP) changes that accompany the tachycardiac conditioned responses (CRs) associated with JM conditioning. The BP response in all instances consisted of a depressor response that was greater to the reinforced CS+ than CS-, although the magnitude of the CR was quite small. The second experiment determined the effects of peripheral autonomic antagonists on the cardiac accelerations associated with JM conditioning. It was found that the peripheral vagal antagonist methyl scopolamine completely abolished responses to both CS+ and CS-, whereas atenolol, a beta adrenergic antagonist, augmented the response, compared to saline control injections. The JM responses were also affected by the autonomic blockades, with minimal responding occurring in the scopolamine group but slightly more JM CRs in the atenolol group, compared to saline control animals. These results suggest that the major cardiovascular response to an appetitive stimulus, which evokes JM conditioning, consists of cardiac accelerations with the BP depressor responses playing a minimal, if any, role. Moreover, these conditioned cardiac increases appear to be due solely to the release of vagal inhibition.     

Excitatory conditioning of individual Drosophila melanogaster

Testing individual animals from a heterogenic population of Drosophila melanogaster, we demonstrate conditioning of the proboscis extension reflex. The presentation of paired (conditioning) stimuli produced (a) an increase in the average number of conditioned responses over trials, (b) measured differences in performance levels among individual subjects, and (c) a sex difference, with more males conditioned than females, and those that did did so more quickly. The presentation of unpaired (control) stimuli produced significantly lower average levels of acquisition responding and a change in the distribution of individual response patterns. Neither central excitatory state nor sensitization induced by the conditioned or unconditioned stimuli directly affected the conditioned response, whereas unconditioned stimulus preexposure adversely affected performance levels. Presenting the unpaired (extinction) stimuli after conditioning produced less of a decline in responding than did an extinction procedure with removal of the unconditioned stimulus. With the ability to identify individual differences in acquisition and extinction patterns, and given the relatively large number of individuals that can be tested simultaneously on the automated stimulation apparatus, it is now possible to make precise behavioral measurements on samples large enough for the behavior-genetic analysis of D. melanogaster with conditioning as the phenotype.     

Wild birds recognize individual humans: experiments on magpies, <Emphasis Type="Italic">Pica pica</Emphasis>

The ability to distinguish among heterospecific individuals has been reported in only a few animal species. Humans can be viewed as a special type of heterospecifics because individuals differ widely in behavior, ranging from non-threatening to very threatening toward animals. In this study, we asked whether wild magpies can recognize individual humans who had accessed their nests. We compared the behavior of breeding pairs toward individual humans before and after the humans climbed up to the birds’ nests, and also toward climbers and non-climbers. We have evidence for (i) aggressive responses of the magpie pairs toward humans who had repeatedly accessed their nests (climbers) and a lack of response to humans who had not accessed the nest (non-climbers); (ii) a total lack of scolding responses toward climbers by magpie pairs whose nests had not been accessed; (iii) a selective aggressive response to the climber when a climber and a non-climber were presented simultaneously. Taken together, these results suggest that wild magpies can distinguish individual humans that pose a threat to their nests from humans that have not behaved in a threatening way. The magpie is only the third avian species, along with crows and mockingbirds, in which recognition of individual humans has been documented in the wild. Here, we propose a new hypothesis (adopted from psychology) that frequent previous exposure to humans in urban habitats contributes to the ability of birds to discriminate among human individuals. This mechanism, along with high cognitive abilities, may predispose some species to learn to discriminate among human individuals. Experimental tests of these two mechanisms are proposed.     

Habituation as a mechanism of reduced aggression between neighboring territorial male bullfrogs (Rana catesbeiana)

Territorial animals often exhibit relatively lower levels of aggression toward familiar territorial neighbors than toward strangers. Habituation to a neighbor or its communication signals has been proposed to account for this reduced aggression between adjacent territorial neighbors. The authors asked whether discrimination between neighbors and strangers by territorial male bullfrogs (Rana catesbeiana) could result from habituation of the aggressive response to repeated presentations of the acoustic communication signals of a simulated new neighbor calling from an adjacent territory. In 3 field playback experiments, the authors found evidence for 5 response characteristics that operationally define habituation. Moreover, aggressive response decrements persisted between nights of chorusing and were specific to an individually distinct property of male advertisement calls. The authors suggest that reduced aggression between neighboring territorial male bullfrogs could result from long-term, stimulus-specific habituation to the advertisement calls of a new neighbor.     

Generalization of aggressive behavior in adolescent delinquent boys

The generalization of conditioned aggressive and nonaggressive responses in a group of six adolescent delinquent boys was investigated. Responses were reinforced in card games where a token reinforcement system with money as a back-up rinforcer was used. Conditioning of responses was rapid. Generalization, measured in terms of frequency of physical contact, was tested in a group game for which no reinforcement was given. Generalization occurred during aggressive contingencies. During nonaggressive contingencies, responses did not return completely to the baseline level.     

Conspecific recognition in the chimpanzee (Pan troglodytes): cardiac responses to significant others

The ability of a chimpanzee (Pan troglodytes) to recognize photographs of conspecifics was evaluated with heart-rate measures. Heart rate was recorded before, during, and after viewing photographs of an aggressive chimpanzee, a friendly companion animal, and an unfamiliar chimpanzee. The subject displayed a differential pattern of heart-rate response to the stimulus animals, without prior experience with the photographs. Responses to the aggressive animal were acceleratory, which suggests a defensive response. Respiratory sinus arrhythmia suggested that this response was associated with sympathetic activation. In contrast, responses to the familiar animal were minimal, whereas cardiac deceleration was observed in response to the strange chimp, which likely reflects an orienting response. Results suggest the chimpanzee is able to recognize photographs of individual conspecifics and that heart-rate change can reflect the nature of established social relationships between chimpanzees.