Some animal specific fears are more specific than others: Evidence from attention and emotion measures

Using a visual search methodology we investigated the effect of feared animal stimuli on attention. Our results confirmed the important role of emotion on attention. All participants detected fear-relevant stimuli (snakes and spiders) faster than neutral (mushrooms) ones against a background of fruits. In addition, spider fearful participants were sensitized specifically to detect their feared stimulus (spiders), compared to their fear-relevant but non-feared (snakes) and neutral stimuli. However, for participants fearful of snakes there was no significant difference in detection latencies between the feared (snakes) and the fear-relevant but non-feared animal stimuli (spiders). The results from the attention task were mirrored in the emotional ratings, which showed that spider fear was highly specific, whereas snake fear was associated with a more generalized enhanced evaluation of all negative stimuli.     

Attentional bias to pictures of fear-relevant animals in a dot probe task

Attentional bias to fear-relevant animals was assessed in 69 participants not preselected on self-reported anxiety with the use of a dot probe task showing pictures of snakes, spiders, mushrooms, and flowers. Probes that replaced the fear-relevant stimuli (snakes and spiders) were found faster than probes that replaced the non-fear-relevant stimuli, indicating an attentional bias in the entire sample. The bias was not correlated with self-reported state or trait anxiety or with general fearfulness. Participants reporting higher levels of spider fear showed an enhanced bias to spiders, but the bias remained significant in low scorers. The bias to snake pictures was not related to snake fear and was significant in high and low scorers. These results indicate preferential processing of fear-relevant stimuli in an unselected sample.     

Snakes and cats in the flower bed: fast detection is not specific to pictures of fear-relevant animals

The observation that snakes and spiders are found faster among flowers and mushrooms than vice versa and that this search advantage is independent of set size supports the notion that fear-relevant stimuli are processed preferentially in a dedicated fear module. Experiment 1 replicated the faster identification of snakes and spiders but also found a set size effect in a blocked, but not in a mixed-trial, sequence. Experiment 2 failed to find faster identification of snake and spider deviants relative to other animals among flowers and mushrooms and provided evidence for a search advantage for pictures of animals, irrespective of their fear relevance. These findings suggest that results from the present visual search task cannot support the notion of preferential processing of fear relevance.     

Reliability and validity of some specific fear questionnaires

Normative psychometric data on a Swedish translation of fear questionnaires concerning snakes, spiders, public speaking, and mutilation given to 223 college students are presented. High internal consistencies were found for all four questionnaires, and low intercorrelations among the four inventories emerged. In a separate study the inventories were administered to a clinical sample of spider and snake phobics. Phobics scored higher on their respective phobic scale than the college group but did not differ from controls on mutilation or public speaking scales. A significant negative correlation emerged between snake and spider scores among the phobics. One year test-retest reliabilities in the phobic sample were high. Finally, snake and spider phobics viewed and rated phobic and nonphobic slides. Snake phobics rated snake slides as more aversive than spider slides, whereas the reverse was true for spider phobics. The correlation between fear ratings and questionnaire scores was significant. Use of these scales in evaluating therapeutic changes is encouraged.     

The relationship between self-reported animal fear and ERP modulation: Evidence for enhanced processing and fear of harmless invertebrates in snake- and spider-fearful individuals

The present study used ERPs to compare processing of fear-relevant (FR) animals (snakes and spiders) and non-fear-relevant (NFR) animals similar in appearance (worms and beetles). EEG was recorded from 18 undergraduate participants (10 females) as they completed two animal-viewing tasks that required simple categorization decisions. Participants were divided on a post hoc basis into low snake/spider fear and high snake/spider fear groups. Overall, FR animals were rated higher on fear and elicited a larger LPC. However, individual differences qualified these effects. Participants in the low fear group showed clear differentiation between FR and NFR animals on subjective ratings of fear and LPC modulation. In contrast, participants in the high fear group did not show such differentiation between FR and NFR animals. These findings suggest that the salience of feared-FR animals may generalize on both a behavioural and electro-cortical level to other animals of similar appearance but of a non-harmful nature.     

Rapid visuomotor processing of phobic images in spider- and snake-fearful participants

This study investigates enhanced visuomotor processing of phobic compared to fear-relevant and neutral stimuli. We used a response priming design to measure rapid, automatic motor activation by natural images (spiders, snakes, mushrooms, and flowers) in spider-fearful, snake-fearful, and control participants. We found strong priming effects in all tasks and conditions; however, results showed marked differences between groups. Most importantly, in the group of spider-fearful individuals, spider pictures had a strong and specific influence on even the fastest motor responses: Phobic primes entailed the largest priming effects, and phobic targets accelerated responses, both effects indicating speeded response activation by phobic images. In snake-fearful participants, this processing enhancement for phobic material was less pronounced and extended to both snake and spider images. We conclude that spider phobia leads to enhanced processing capacity for phobic images. We argue that this is enabled by long-term perceptual learning processes.     

Attention control: Relationships between self-report and behavioural measures,and symptoms of anxiety and depression

Previous research has demonstrated differences in processing between fear-relevant stimuli, such as snakes and spiders, and non-fear-relevant stimuli. The current research examined whether non-fear-relevant animal stimuli, such as dogs, birds and fish, were processed like fear-relevant stimuli following aversive learning. Pictures of a priori fear-relevant animals, snakes and spiders, were evaluated as negative in affective priming and ratings and were preferentially attended to in a visual search task. Pictures of dogs, birds and fish that had been trained as CS+ in an aversive conditioning design were evaluated more negatively and facilitated dot probe detection relative to CS? pictures. The current studies demonstrated that stimuli viewed as positive prior to aversive learning were negative and were preferentially attended to after a brief learning episode. We propose that aversive learning may provide a mechanism for the acquisition of stimulus fear relevance.     

Threat-relevance impairs executive functions: negative impact on working memory and response inhibition

The effects of emotional stimulus content on attention are well-known. In contrast, the impact of emotional information on higher executive control functions is undetermined. To elucidate the role of negative emotion in cognitive control, 56 adult female participants performed a combined working memory and response inhibition task, with threat-relevant (spider and snake) and neutral (flower and mushroom) stimuli. Threat-relevant stimuli impaired performance, by causing prolonged response times to working memory items and increased response inhibition error rate relative to neutral stimuli. The impaired response inhibition was only evident when threat-relevant stimuli co-occurred with working memory matches, in line with a common resource pool view of executive functions and emotion processing. Individual differences in reported fear of spiders were associated with differences of inhibitory control, while fear of snakes was associated with impaired overall accuracy on working memory trials. The results are discussed in relation to the dual-competition framework for interaction between executive functions and emotion (Pessoa, 2009).     

The influence of animal fear on attentional capture by fear-relevant animal stimuli in children

The present study demonstrated that pictures of fear-relevant animals, snakes and spiders, presented among backgrounds of other animal stimuli captured attention and interfered in the detection of a neutral target to the same extent in a large sample of unselected children (N=81). Moreover, detection of a neutral target animal was slowed more in the presence of a feared fear-relevant distracter, e.g., a snake for snake fearful children, than in the presence of a not feared fear-relevant distracter, e.g., a spider for snake fearful children. These results indicate attentional capture by phylogenetically fear-relevant animal stimuli in children and the selective enhancement of this effect by fear of these animals. These findings are consistent with current models of preferential processing of phylogenetically prepared threat stimuli and with cognitive models of anxiety that propose an enhancing effect of fear in the processing of fear-related stimuli.     

Animal phobias versus claustrophobias: Exteroceptive versus interoceptive cues

The overall purpose of this investigation was to examine heterogeneity among specific phobias. In particular, the goals were to compare features of fear responding between individuals fearful of claustrophobic situations and individuals fearful of spiders/snakes, and to compare their response to hyperventilation challenges. By so doing, specific predictions were tested in relation to a conceptual model of exteroceptive and interoceptive fear cues. Using a nonclinical sample, 19 subjects with spider/snake phobias, 18 nonphobies, and 9 subjects with claustrophobias were exposed on two separate occasions to a live tarantula or python, a small closet, and a hyperventilation challenge. Dependent measures included subjective anxiety, panic attacks, physical symptoms, cognitive symptoms (or, fear of symptoms) and heart rate. In addition, subjects completed a standardized self-report scale that measures fear of bodily symptoms of arousal. It was found that subjects with claustrophobia reported more physical symptoms and cognitive symptoms than did subjects with snake/spider phobias, in response to their fear-relevant stimulus. In addition, claustrophobic subjects were more fearful of hyperventilation challenges and reported more fear of bodily symptoms, than did snake/spider phobic subjects. Finally, subjects with claustrophobia were as fearful of hyperventilation as they were of their fear-relevant stimulus. Theoretical and empirical implications of these findings are discussed.     

The time course of resource allocation in spider-fearful participants during fear reactions

The dynamics of resource allocation to pictures of spiders and other animals in spider-fearful participants was investigated. The task of the participants was to respond rapidly and accurately to various probe stimuli superimposed on pictures of different animals. These were arguably fear relevant (spiders, snakes, and wolves) and fear irrelevant (beetles, turtles, and rabbits). The probes were shown with different stimulus onset asynchronies (SOAs) from picture onset to address the dynamics of resource allocation. A larger allocation of resources to spider pictures than to pictures of all other animals, with no difference between the latter regarding resource allocation was found. For the task that demanded more resources the fear-related physiological responses decreased, suggesting that controlled processing modulates fear responses.     

Visual search with animal fear-relevant stimuli: A tale of two procedures

The present study assessed preferential attentional processing of animal fear-relevant stimuli in two procedures, Search and Interference tasks, which have been suggested to reflect on attentional capture due to the fear-relevance of the stimuli presented. In the Search task, participants (N = 154) searched fear-relevant (i.e., snakes and spiders) and non fear-relevant (i.e., fish and birds) backgrounds to determine the presence or absence of a deviant animal from the opposite category. In the Interference task, the same participants searched for the presence or absence of a neutral target (a cat) when either a snake, spider or no distracter were embedded amongst backgrounds of other animal stimuli. Replicating previous findings, preferential attentional processing of animal fear-relevant stimuli was evident in both procedures and participants who specifically feared one animal but not the other showed enhanced preferential processing of their feared fear-relevant animal. However, across the entire sample, there was no relationship between self-reported levels of animal fear and preferential processing which may reflect on the fact that substantial preferential attentional processing of fear-relevant animals was evident in the entire sample. Also, preferential attentional processing as assessed in the two tasks was not related. Delayed disengagement from fear-relevant stimuli appeared to underlie performance in the search task but not in the interference task.     

The role of fear and expectancies in capture of covert attention by spiders

Fear-related stimuli are often prioritized during visual selection but it remains unclear whether capture by salient objects is more likely to occur when individuals fear those objects. In this study, participants with high and low fear of spiders searched for a circle while on some trials a completely irrelevant fear-related (spider) or neutral distractor (butterfly/leaf) was presented simultaneously in the display. Our results show that when you fear spiders and you are not sure whether a spider is going to be present, then any salient distractor (i.e., a butterfly) grabs your attention, suggesting that mere expectation of a spider triggered compulsory monitoring of all irrelevant stimuli. However, neutral stimuli did not grab attention when high spider fearful people knew that a spider could not be present during a block of trials, treating the neutral stimuli just as the low spider fearful people do. Our results show that people that fear spiders inspect potential spider-containing locations in a compulsory fashion even though directing attention to this location is completely irrelevant for the task. Reduction of capture can only be accomplished when people that fear spiders do not expect a spider to be present.     

Visual search with biological threat stimuli: accuracy, reaction times, and heart rate changes

Twenty-four participants were given a visual search task of deciding whether all the pictures in 3 x 3 search arrays contained a target picture from a deviant category, and heart rate was measured. The categories were snakes, spiders, flowers, and mushrooms. Shorter reaction times (RTs) were observed for fear-relevant (snake and spider) targets rather than for fear-irrelevant/neutral (flower and mushroom) targets. This difference was most pronounced for the participants presented with a gray-scale version of the search arrays. The 1st interbeat interval (IBI), after the search array onset, showed an effect of the target, whereas the 2nd IBI also showed an effect of the distractors. The results suggest that controlled processing of the task operates together with automatic processing.     

The effect of visual threat on spatial attention to touch

Viewing a threatening stimulus can bias visual attention toward that location. Such effects have typically been investigated only in the visual modality, despite the fact that many threatening stimuli are most dangerous when close to or in contact with the body. Recent multisensory research indicates that a neutral visual stimulus, such as a light flash, can lead to a tactile attention shift towards a nearby body part. Here, we investigated whether the threat value of a visual stimulus modulates its effect on attention to touch. Participants made speeded discrimination responses about tactile stimuli presented to one or other hand, preceded by a picture cue (snake, spider, flower or mushroom) presented close to the same or the opposite hand. Pictures of snakes led to a significantly greater tactile attentional facilitation effect than did non-threatening pictures of flowers and mushrooms. Furthermore, there was a correlation between self-reported fear of snakes and spiders and the magnitude of early facilitation following cues of that type. These findings demonstrate that the attentional bias towards threat extends to the tactile modality and indicate that perceived threat value can modulate the cross-modal effect that a visual cue has on attention to touch.     

Automatic processing in spider phobia: implicit fear associations over the course of treatment

This study evaluates the cognitive model of anxiety by investigating treatment-related changes in automatic associations to evaluate schematic processing. Spider-phobic participants (n = 31) and healthy controls (n = 30) completed fear-based Implicit Association Tests (IATs), which are reaction-time measures that tap implicit associations without requiring conscious introspection. The specific tasks involved classifying pictures of snakes and spiders along with semantic categorizations (good vs.bad, afraid vs. unafraid, danger vs. safety, and disgusting vs. appealing). Phobic individuals were assessed before and after group-based exposure treatment and 2 months later, controls were assessed at matched time points. Results supported clinical applications for implicit fear associations, including prediction of phobic avoidance, and treatment sensitivity of the fear- and disgust-specific automatic associations.     

From fear to love: individual differences in implicit spider associations

The Implicit Association Test (IAT) was used to investigate automatic fear associations in fear of spiders. Fear associations toward spiders were measured among spider fearful and nonfearful participants (Experiment 1) as well as among nonfearfuls and spider enthusiasts (Experiment 2). It was shown that the IAT is sensitive to personal automatic fear associations and therefore distinguishes between high-fearful, nonfearful, and enthusiastic participants. Moreover, implicit spider associations measured by the IAT predicted avoidance behavior beyond self-reports. The results of Experiment 2 provide additional support for the argument that implicit spider associations are different from general stereotypes or knowledge about spiders.     

The lurking snake in the grass: Interference of snake stimuli in visually taxing conditions

Based on evolutionary considerations, it was hypothesized that humans have been shaped to easily spot snakes in visually cluttered scenes that might otherwise hide camouflaged snakes. This hypothesis was tested in a visual search experiment in which I assessed automatic attention capture to evolutionarily-relevant distractor stimuli (snakes), in comparison with another animal which is also feared but where this fear has a disputed evolutionary origin (spiders), and neutral stimuli (mushrooms). Sixty participants were engaged in a task that involved the detection of a target (a bird) among pictures of fruits. Unexpectedly, on some trials, a snake, a spider, or a mushroom replaced one of the fruits. The question of interest was whether the distracting stimuli slowed the reaction times for finding the target (the bird) to different degrees. Perceptual load of the task was manipulated by increments in the set size (6 or 12 items) on different trials. The findings showed that snake stimuli were processed preferentially, particularly under conditions where attentional resources were depleted, which reinforced the role of this evolutionarily-relevant stimulus in accessing the visual system (Isbell, 2009).     

Of snakes and flowers: does preferential detection of pictures of fear-relevant animals in visual search reflect on fear-relevance?

Previous research in visual search indicates that animal fear-relevant deviants, snakes/spiders, are found faster among non fear-relevant backgrounds, flowers/mushrooms, than vice versa. Moreover, deviant absence was indicated faster among snakes/spiders and detection time for flower/mushroom deviants, but not for snake/spider deviants, increased in larger arrays. The current research indicates that the latter 2 results do not reflect on fear-relevance, but are found only with flower/mushroom controls. These findings may reflect on factors such as background homogeneity, deviant homogeneity, or background-deviant similarity. The current research removes contradictions between previous studies that used animal and social fear-relevant stimuli and indicates that apparent search advantages for fear-relevant deviants seem likely to reflect on delayed attentional disengagement from fear-relevance on control trials.