Verbal instruction abolishes fear conditioned to racial out-group faces

Previous research has shown resistance to extinction of fear conditioned to racial out-group faces, suggesting that these stimuli may be subject to prepared fear learning. The current study replicated and extended previous research by using a different racial out-group, and testing the prediction that prepared fear learning is unaffected by verbal instructions. Four groups of Caucasian participants were trained with male in-group (Caucasian) or out-group (Chinese) faces as conditional stimuli; one paired with an electro-tactile shock (CS+) and one presented alone (CS−). Before extinction, half the participants were instructed that no more shocks would be presented. Fear conditioning, indexed by larger electrodermal responses to, and blink startle modulation during the CS+, occurred during acquisition in all groups. Resistance to extinction of fear learning was found only in the racial out-group, no instruction condition. Fear conditioned to a racial out-group face was reduced following verbal instructions, contrary to predictions for the nature of prepared fear learning.     

Measuring the role of conditioning and stimulus generalisation in common fears and worries

Common and persistent fears may emerge through learning mechanisms such as fear conditioning and generalisation. Although there have been extensive studies of these learning processes in healthy but also psychiatric samples, many of the tasks used to produce conditioning and assess generalisation either use painful and aversive stimuli as the unconditioned stimuli (UCS), or suffer from poor belongingness between the conditioned stimuli and the UCS. Here, we present novel data from a paradigm designed to examine fear conditioning and generalisation in healthy individuals. Two female faces served as conditioned threat cue (CS+) and conditioned safety cue (CS?) respectively. The CS+ was paired repeatedly with a fearful, screaming face (unconditioned stimulus). Generalisation included intermediate faces which varied in their similarity to the CS+ and CS?. We measured eyeblink startle reflex and self-reported ratings. Acquired fear of the CS+ generalised to intermediate stimuli in proportion to their perceptual similarity to the CS+. Our findings demonstrate how fears of new individuals may develop based on resemblance to others with whom an individual has had negative experiences. The paradigm offers new opportunities for probing the role of generalisation in the emergence of common and persistent fears.     

Goal relevance moderates evaluative conditioning effects

An important process by which preferences emerge is evaluative conditioning, defined as a change in the evaluation of a stimulus by pairing it repeatedly and consistently with an affective stimulus. The current research focuses on the role of motivation in this learning process. Specifically, it was investigated whether a conditioning procedure that is relevant to an individual's current goals is more effective than an irrelevant procedure. To this end, beverages were conditioned with either disgusted faces (relevant) or fearful faces (irrelevant). The results showed that thirsty(rather than non-thirsty) participants’ choice and evaluation of beverages were influenced by pairing beverages with disgust but not with fear. As similar results were obtained under optimal and suboptimal presentation of the conditioned stimuli, it is suggested that goals can affect automatic, associative learning, adding to the emerging body of research demonstrating that goals unconsciously affect evaluative processes.     

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.     

Learning to fear a second-order stimulus following vicarious learning

Vicarious fear learning refers to the acquisition of fear via observation of the fearful responses of others. The present study aims to extend current knowledge by exploring whether second-order vicarious fear learning can be demonstrated in children. That is, whether vicariously learnt fear responses for one stimulus can be elicited in a second stimulus associated with that initial stimulus. Results demonstrated that children's (5–11 years) fear responses for marsupials and caterpillars increased when they were seen with fearful faces compared to no faces. Additionally, the results indicated a second-order effect in which fear-related learning occurred for other animals seen together with the fear-paired animal, even though the animals were never observed with fearful faces themselves. Overall, the findings indicate that for children in this age group vicariously learnt fear-related responses for one stimulus can subsequently be observed for a second stimulus without it being experienced in a fear-related vicarious learning event. These findings may help to explain why some individuals do not recall involvement of a traumatic learning episode in the development of their fear of a specific stimulus.     

Non-specific effect of fear conditioning and specific effect of social defeat on social recognition memory performance in female rats

The so called "emotion learning" literature describes the ability of distressing and aversive unconditioned stimuli to classically condition a learned avoidance response. In order to investigate the impact of experience with noxious stimuli in one conditioning context on learning and memory performance in a separate, non-aversively motivated task, juvenile recognition ability was examined in adult female rats exposed previously to one of two environmental stressors. In particular, experimental adult rats were either socially defeated by exposure to an aggressive conspecific rat or fear conditioned using single or multiple pairings with footshock prior to performance of the social recognition task. Experiment 1 established that repeated exposure to a single juvenile resulted in social memory formation reflected in decreased social investigation from the first to the second exposure. Experiment 2 documented that both single and multiple pairings of an environment with footshock produced robust freezing behavior (90-95% suppression of activity). In addition, fear conditioning produced a non-specific 5-60% increase in social investigation time in both single and multiple-pairing fear conditioned groups which confounded the ability of the social recognition measure to assess effects of fear conditioning on learning and memory performance per se. In contrast, Experiment 3 documented that when social recognition memory performance was impaired to 85% of control levels by imposition of a 2 h delay, exposure to a social defeat stressor reinstated optimal social recognition memory performance. These findings suggest that the after effects of fear conditioning include non-specific alteration of social investigation whereas exposure to conspecific aggression enhances subsequent social recognition memory.     

Excitatory strength of expressive faces: effects of happy and fear expressions and context on the extinction of a conditioned fear response

In a recent study, Orr and Lanzetta (1984) showed that the excitatory properties of fear facial expressions previously described (Lanzetta & Orr, 1981; Orr & Lanzetta, 1980) do not depend on associative mechanisms; even in the absence of reinforcement, fear faces intensify the emotional reaction to a previously conditioned stimulus and disrupt extinction of an acquired fear response. In conjunction with the findings on acquisition, the failure to obtain extinction suggests that fear faces have some of the functional properties of "prepared" (fear-relevant) stimuli. In the present study we compared the magnitude of conditioned fear responses to happy and fear faces when a potent danger signal, the shock electrodes, are attached or unattached. If fear faces are functionally analogous to prepared stimuli, then, even in the absence of veridical support for an expectation of shock, they should retain excitatory strength, whereas happy faces should not. The results are consistent with this view of fear expressions. In the absence of reinforcement, and with shock electrodes removed, conditioned fear responses and basal levels of arousal were of greater magnitude for the fear-face condition than for the happy-face condition.     

Investigating the effectiveness of brief cognitive reappraisal training to reduce fear in adolescents

As adolescent anxiety is common and costly, identifying effective strategies to reduce symptoms is a priority. This study tested whether adolescents could learn to use cognitive reappraisal strategies to attenuate fear during extinction learning. Fifty-seven participants (12–15 years) viewed images of two neutral faces, one which was paired with a fearful expression and shrieking scream (conditioned threat stimulus) and the other that was never paired with the aversive outcome (conditioned safety stimulus) during fear acquisition. Before extinction, participants either received cognitive appraisal training, which explored alternative, benign meanings associated with the scream or a control activity. Self-reported fear ratings in the cognitive reappraisal group were significantly lower to both the conditioned threat and safety stimuli after extinction than the control group. These findings did not characterise fear-potentiated startle data. Potential reasons for the lack of consistency between measures are considered.     

Social fear and expressive reactions to social stimuli

This study explored whether subjects high as compared to low in social fear react with a more negative emotional response, measured as facial electromyographic (EMG) activity, when exposed to social stimuli (pictures of angry and happy facial expressions). It was found that subjects who rated themselves as relatively high in public speaking fear gave larger negative facial EMG responses (Corrugator supercilii muscle activity) to angry faces than did the low fear subjects. Low fear subjects, on the other hand, gave larger positive facial EMG responses (Zygomatic major muscle activity) to happy faces than did the high fear subjects. It was further found that happy stimuli were rated as more hostile and less friendly and happy by the high fear group. Consistent with earlier findings, it was concluded that the facial EMG technique is sensitive to detecting different reactions among subjects relatively high and low in social fear.     

How do social fears in adolescence develop? Fear conditioning shapes attention orienting to social threat cues

Social fears emerging in adolescence can have negative effects on emotional well-being. Yet the mechanisms by which these risks occur are unknown. One possibility is that associative learning results in fears to previously neutral social stimuli. Such conditioned responses may alter subsequent processing of social stimuli. We used a novel conditioning task to examine how associative processes influence social fear and attention orienting in adolescents. Neutral photographs were paired with socially rewarding or aversive stimuli during conditioning; a dot-probe task then assessed biases in attention orienting. The social conditioning task modified subjective ratings of the neutral stimuli. Moreover, for the neutral stimulus that was paired with the aversive stimulus, the strength of conditioning showed a relationship with subsequent attentional vigilance. The findings elucidate mechanisms by which negative peer experiences during adolescence may affect emotional processing.     

Social modulation of learning in rats

It is well known that emotions participate in the regulation of social behaviors and that the emotion displayed by a conspecific influences the behavior of other animals. In its simplest form, empathy can be characterized as the capacity to be affected by and/or share the emotional state of another. However, to date, relatively little is known about the mechanisms by which animals that are not in direct danger share emotions. In the present study, we used a model of between-subject transfer of fear to characterize the social interaction during which fear is transmitted, as well as the behavioral effects of socially transmitted fear. We found that (1) during social interaction with a recently fear-conditioned partner, observers and demonstrators exhibit social exploratory behaviors rather than aggressive behaviors; (2) learning and memory in a shock-motivated shuttle avoidance task are facilitated in rats that underwent a social interaction with a partner that had been fear conditioned; and (3) a brief social interaction with a recently fear-conditioned partner immediately before fear conditioning increases conditioned freezing measured on the next day. The observed effects were not due to a stress-induced increase in pain sensitivity or analgesia. Collectively, these data suggest that a brief social interaction with a cage mate that has undergone an aversive learning experience promotes aversive learning in an otherwise naïve animal. We argue that socially transferred fear is an adaptation that promotes defensive behavior to potentially dangerous situations in the environment.Human empathy can be defined as the ability to experience and share the thoughts and feelings of others (de Waal 2008). Obviously, this is a complex social phenomenon that, until recently, has received much attention from philosophers and psychologists rather than neuroscientists (Decety and Lamm 2006). However, in its simplest form, empathy can be characterized as the capacity to be affected by and/or share the emotional state of another (de Waal 2008). Tuning one''s emotional state to that of another increases the probability of similar behavior, which thereby allows rapid adaptation to environmental challenges (Hatfield et al. 1994). This social adaptation may be particularly important for emotions that signal a potential danger, such as fear. Although one can learn about potentially harmful stimuli by directly experiencing an aversive event, observation or interaction with a conspecific in danger and/or in pain may also provide information about threats in the environment. There is a vast literature on learning about direct danger (Maren 2001) as well as sharing emotions through observation (see, e.g., Church 1959; Langford et al. 2006; Olsson and Phelps 2007). However, relatively little is known about the mechanisms by which animals that are not in a direct danger share emotions.We have recently designed an experimental rat model of between-subject transfer of emotional information (Knapska et al. 2006). In this model, rats are housed in pairs and one member of the pair (the “demonstrator”) is removed and subjected to fear conditioning. After the fear-conditioning episode, the conditioned animal is allowed to interact with its naïve cage mate (the “observer”). We showed that the demonstrator''s fear is socially transferred to the observer, resulting in both rapid increase in exploratory behavior of the observer and a pattern of c-Fos activation in the observer''s amygdala that parallels that of the shocked demonstrators.These results suggest that the social interaction between the demonstrator and observer results in a transfer of information that promotes aversively motivated learning in the observer. However, the nature of the social interaction and how it comes to influence aversively motivated behavior is not known. Therefore, the present study aimed to characterize the behavior of both the demonstrators and observers during their social interaction and further characterize the nature of the influence of socially transmitted fear on aversively motivated learning and memory. We hypothesized that the social interaction between observers and demonstrators would result in a social transfer of fear that would promote learning and memory of both active defensive responses (avoidance) as well as defensive immobility (freezing). To test this hypothesis, we carried out five experiments that examined the nature of the social interaction between shocked demonstrators and observers (Experiment 1), the acquisition and retention of active avoidance (Experiment 2), and conditioned freezing (Experiment 3). Because it is not clear if social transfer effects can be observed among unfamiliar animals and to control for social buffering, we also compared the social transfer of fear in familiar and unfamiliar rats (Experiment 4). To control for the possible influence of different pain sensitivity thresholds in the observers paired with shocked demonstrators, we carried out pain tests (Experiment 5).     

How do social fears in adolescence develop? Fear conditioning shapes attention orienting to social threat cues

Social fears emerging in adolescence can have negative effects on emotional well-being. Yet the mechanisms by which these risks occur are unknown. One possibility is that associative learning results in fears to previously neutral social stimuli. Such conditioned responses may alter subsequent processing of social stimuli. We used a novel conditioning task to examine how associative processes influence social fear and attention orienting in adolescents. Neutral photographs were paired with socially rewarding or aversive stimuli during conditioning; a dot-probe task then assessed biases in attention orienting. The social conditioning task modified subjective ratings of the neutral stimuli. Moreover, for the neutral stimulus that was paired with the aversive stimulus, the strength of conditioning showed a relationship with subsequent attentional vigilance. The findings elucidate mechanisms by which negative peer experiences during adolescence may affect emotional processing.     

Awareness of faces is modulated by their emotional meaning

A central question in perception is how stimuli are selected for access to awareness. This study investigated the impact of emotional meaning on detection of faces using the attention blink paradigm. Experiment 1 showed that fearful faces were detected more frequently than neutral faces, and Experiment 2 revealed preferential detection of fearful faces compared with happy faces. To rule out image artifacts as a cause for these results, Experiment 3 manipulated the emotional meaning of neutral faces through fear conditioning and showed a selective increase in detection of conditioned faces. These results extend previous reports of preferential detection of emotional words or schematic objects and suggest that fear conditioning can modulate detection of formerly neutral stimuli.     

分类和概念对恐惧泛化的影响机制

恐惧泛化与多种焦虑障碍的病理基础密切相关。例如创伤后应激障碍个体往往持续地逃避与创伤事件有关的刺激,遭受着创伤痛苦折磨。本文在厘清知觉辨别与恐惧泛化关系的基础上,着力于高级认知过程(分类与概念相似性、典型性和人工概念)对恐惧泛化的影响,回顾了恐惧泛化的相关神经机制,并揭示恐惧泛化对焦虑障碍患者的临床治疗启示。未来研究应将知觉和高级认知维度的恐惧泛化进行整合研究,同时扩充恐惧习得和泛化的神经回路,以促进人类恐惧泛化更深入的研究。     

Social transmission of Pavlovian fear: fear-conditioning by-proxy in related female rats

Pairing a previously neutral conditioned stimulus (CS; e.g., a tone) to an aversive unconditioned stimulus (US; e.g., a foot-shock) leads to associative learning such that the tone alone will elicit a conditioned response (e.g., freezing). Individuals can also acquire fear from a social context, such as through observing the fear expression of a conspecific. In the current study, we examined the influence of kinship/familiarity on social transmission of fear in female rats. Rats were housed in triads with either sisters or non-related females. One rat from each cage was fear conditioned to a tone CS+ shock US. On day two, the conditioned rat was returned to the chamber accompanied by one of her cage mates. Both rats were allowed to behave freely, while the tone was played in the absence of the foot-shock. The previously untrained rat is referred to as the fear-conditioned by-proxy (FCbP) animal, as she would freeze based on observations of her cage-mate’s response rather than due to direct personal experience with the foot-shock. The third rat served as a cage-mate control. The third day, long-term memory tests to the CS were performed. Consistent with our previous application of this paradigm in male rats (Bruchey et al. in Behav Brain Res 214(1):80–84, 2010), our results revealed that social interactions between the fear conditioned and FCbP rats on day two contribute to freezing displayed by the FCbP rats on day three. In this experiment, prosocial behavior occurring at the termination of the cue on day two was significantly greater between sisters than their non-sister counterparts, and this behavior resulted in increased freezing on day three. Our results suggest that familiarity and/or kinship influences the social transmission of fear in female rats.     

The Effect of Counterconditioning on Evaluative Responses and Harm Expectancy in a Fear Conditioning Paradigm

In fear conditioning, extinction targets harm expectancy as well as the fear response, but it often fails to eradicate the negative affective value that is associated with the conditioned stimulus. In the present study, we examined whether counterconditioning can serve to reduce evaluative responses within fear conditioning. The sample consisted of 70 nonselected students, 12 of whom were men. All participants received acquisition with human face stimuli as the conditioned stimuli and an unpleasant white noise as the unconditioned stimulus. After acquisition, one third of the sample was allocated to an extinction procedure. The other participants received counterconditioning with either a neutral stimulus (neutral tone) or a positive stimulus (baby laugh). Results showed that counterconditioning (with both neutral and positive stimuli), in contrast to extinction, successfully reduced evaluative responses. This effect was found on an indirect measure (affective priming task), but not on self-report. Counterconditioning with a positive stimulus also tended to enhance the reduction of conditioned skin conductance reactivity. The present data suggest that counterconditioning procedures might be a promising approach in diminishing evaluative learning and even expectancy learning in the context of fear conditioning.     

Facial reactions to facial expressions in subjects high and low in public speaking fear

This study investigated whether subjects high and low in public speaking fear react with different facial electromyographic (EMG) activities when exposed to negative and positive social stimuli. A High-fear and Low-fear group were selected by help of a questionnaire and were exposed to slides of angry and happy faces while facial-EMG from the corrugator and zygomatic muscle regions were measured. The subjects also rated the stimuli on different emotional dimensions. Consistent with earlier research it was found that Low fear subjects reacted with increased corrugator activity to angry faces and increased zygomatic activity to happy faces. The High fear group, on the other hand, did not distinguish between angry and happy faces. Rating data indicated that the High fear group perceived angry faces as being emotionally more negative. The present results are consistent with earlier studies, indicating that the facial-EMG technique is sensitive to detect differential responding among clinical interesting groups, such as people suffering from social fears.     

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.     

Fear conditioning and social groups: statistics, not genetics

Humans display more conditioned fear when the conditioned stimulus in a fear conditioning paradigm is a picture of an individual from another race than when it is a picture of an individual from their own race ( Olsson, Ebert, Banaji, & Phelps, 2005 ). These results have been interpreted in terms of a genetic "preparedness" to learn to fear individuals from different social groups ( Ohman, 2005 ; Olsson et al., 2005 ). However, the associability of conditioned stimuli is strongly influenced by prior exposure to those or similar stimuli. Using the Kalman filter, a normative statistical model, this article shows that superior fear conditioning to individuals from other groups is precisely what one would expect if participants perform optimal, Bayesian inference that takes their prior exposures to the different groups into account. There is therefore no need to postulate a genetic preparedness to learn to fear individuals from other races or social groups.     

Reinstatement of fear responses in human aversive conditioning

The treatment of choice for a number of anxiety disorders is exposure therapy. However, successful reduction of fear through exposure is sometimes followed by a (partial) return of symptoms of fear (return of fear, ROF; Clin. Psychol. Rev. 9 (1989) 147). Several possible learning mechanisms have been suggested to explain ROF (e.g. mechanisms related to spontaneous recovery, renewal, reacquisition and reinstatement). The present study focuses on reinstatement, which refers to the observation that mere US-only presentations can 'reinstate' previously extinguished fear responses. Although animal research has repeatedly demonstrated this phenomenon, little is known about fear reinstatement in humans. The present study employed a differential aversive conditioning procedure: after acquisition and a subsequent extinction procedure, a series of four unpredicted US-only trials was scheduled in the reinstatement group. The control group did not receive additional US presentations. A significant reinstatement effect was observed for US-expectancy ratings and fear ratings in the reinstatement group, but not in the control group. No differences were observed in a reaction time measure of resource allocation to the conditioned stimuli. These findings constitute a first demonstration of reinstatement of conditioned fear responses in humans. Implications for exposure treatment and suggestions for future research are discussed.