Affective states leak into movement execution: Automatic avoidance of threatening stimuli in fear of spider is visible in reach trajectories

Approach-like actions are initiated faster with stimuli of positive valence. Conversely, avoidance-like actions are initiated faster with threatening stimuli of negative valence. We went beyond reaction time measures and investigated whether threatening stimuli also affect the way in which an action is carried out. Participants moved their hand either away from the picture of a spider (avoidance) or they moved their hand toward the picture of a spider (approach). We compared spider-fearful participants to non-anxious participants. When reaching away from the threatening spider picture, spider-fearful participants moved more directly to the target than controls. When reaching toward the threatening spider, spider-fearful participants moved less directly to the target than controls. Some conditions that showed clear differences in movement trajectories between spider-fearful and control participants were devoid of differences in reaction time. The deviation away from threatening stimuli provides evidence for the claim that affective states like fear leak into movement programming and produce deviations away from threatening stimuli in movement execution. Avoidance of threatening stimuli is rapidly integrated into ongoing motor behaviour in order to increase the distance between the participant's body and the threatening stimulus.     

Rapid processing of closure and viewpoint-invariant symmetry: behavioral criteria for feedforward processing

To pin down the processing characteristics of symmetry and closure in contour processing, we investigated their ability to activate rapid motor responses in a primed flanker task. In three experiments, participants selected as quickly and accurately as possible the one of two target contours possessing symmetry or closure. Target pairs were preceded by prime pairs whose spatial arrangement was consistent or inconsistent with respect to the required response. We tested for the efficiency and automaticity of symmetry and closure processing. For both cues, priming effects were present in full magnitude in the fastest motor responses consistent with a simple feedforward model. Priming effects from symmetry cues were independent of skewing and the orientation of their symmetry axis but sometimes failed to increase with increasing prime-target interval. We conclude that closure and (possibly) viewpoint-independent symmetry cues are extracted rapidly during the first feedforward wave of neuronal processing.     

Evidence for an encounter expectancy bias in fear of spiders

Whereas research has demonstrated that phobic or fearful individuals overestimate the likelihood of incurring aversive consequences from an encounter with feared stimuli, it has not yet been systematically investigated whether these individuals also overestimate the likelihood (i.e., the frequency) of such encounters. In the current study, spider-fearful and control participants were presented with background information that allowed them to estimate the overall likelihood that different kinds of animals (spiders, snakes, or birds) would be encountered. Spider-fearful participants systematically overestimated the likelihood of encountering a spider with respect to the likelihood of encountering a snake or a bird. No such expectancy bias was observed in control participants. The results thus strengthen our idea that there indeed exist two different types of expectancy bias in high fear and phobia that can be related to different components of the fear response. A conscientious distinction and examination of these two types of expectancy bias are of potential interest for therapeutic applications.     

When danger lurks in the background: attentional capture by animal fear-relevant distractors is specific and selectively enhanced by animal fear

Across 2 experiments, a new experimental procedure was used to investigate attentional capture by animal fear-relevant stimuli. In Experiment 1 (N=34), unselected participants were slower to detect a neutral target animal in the presence of a spider than a cockroach distractor and in the presence of a snake than a large lizard distractor. This result confirms that phylogenetically fear-relevant animals capture attention specifically and to a larger extent than do non-fear-relevant animals. In Experiment 2 (N=86), detection of a neutral target animal was slowed more in the presence of a feared fear-relevant distractor (e.g., a snake for snake-fearful participants) than in presence of a not-feared fear-relevant distractor (e.g., a spider for snake-fearful participants). These results indicate preferential attentional capture that is specific to phylogenetically fear-relevant stimuli and is selectively enhanced in individuals who fear these animals.     

Qualitative differences between conscious and nonconscious processing? On inverse priming induced by masked arrows

In general, both consciously and unconsciously perceived stimuli facilitate responses to following similar stimuli. However, masked arrows delay responses to following arrows. This inverse priming has been ascribed to inhibition of premature motor activation, more recently even to special processing of nonconsciously perceived material. Here, inverse priming depended on particular masks, was insensitive to contextual requirements for increased inhibition, and was constant across response speeds. Putative signs of motor inhibition in the electroencephalogram may as well reflect activation of the opposite response. Consequently, rather than profiting from inhibition of primed responses, the alternative response is directly primed by perceptual interactions of primes and masks. Thus there is no need to assume separate pathways for nonconscious and conscious processing.     

The effect of very brief exposure on experienced fear after in vivo exposure

Two experiments tested the effect of exposure to masked phobic stimuli at a very brief stimulus onset asynchrony on reducing the subjective experience of fear caused by in vivo exposure to a feared object. In the main experiment, 35 spider-fearful and 35 non-fearful participants were identified with a questionnaire and a Behavioural Avoidance Test (BAT) with a live tarantula. One week later, they were individually administered one of two continuous series of masked images: spiders or flowers. They engaged in the BAT again immediately thereafter. They provided ratings of subjective fear at the end of each BAT (pre- and post-manipulation). Very brief exposure to images of spiders reduced the fearful group's and not the non-fearful group's experience of fear at the end of the BAT. This effect was replicated with another sample of 26 spider-fearful participants from the same population. Theoretical implications are discussed.     

Evidence for an encounter expectancy bias in fear of spiders

Whereas research has demonstrated that phobic or fearful individuals overestimate the likelihood of incurring aversive consequences from an encounter with feared stimuli, it has not yet been systematically investigated whether these individuals also overestimate the likelihood (i.e., the frequency) of such encounters. In the current study, spider-fearful and control participants were presented with background information that allowed them to estimate the overall likelihood that different kinds of animals (spiders, snakes, or birds) would be encountered. Spider-fearful participants systematically overestimated the likelihood of encountering a spider with respect to the likelihood of encountering a snake or a bird. No such expectancy bias was observed in control participants. The results thus strengthen our idea that there indeed exist two different types of expectancy bias in high fear and phobia that can be related to different components of the fear response. A conscientious distinction and examination of these two types of expectancy bias are of potential interest for therapeutic applications.     

Inverse cue priming is not limited to masks with relevant features

Apart from positive priming effects, masked prime stimuli can impair responses to a subsequent target stimulus which shares response-critical features in contrast to a target assigned to the opposite response. This counterintuitive phenomenon is called inverse priming (or negative compatibility effect). Here we examine the generality of this phenomenon beyond priming of motor responses. We used a non-motor cue-priming paradigm to study the underlying mechanism of inverse priming for relevant features masks which include task-relevant stimulus features and for irrelevant masks which omit task-relevant features. We found inverse cue-priming effects with both types of masks. With task-irrelevant masks inverse cue-priming was emphasized in those participants being unable to perceive the prime. The existence of inverse non-motor priming under conditions where simple perceptual interactions between the stimuli are ruled out as the source of inverse priming is at odds with the view that inverse priming reflects motor inhibition. Alternatives are discussed.     

Time course of free-choice priming effects explained by a simple accumulator model

Unconscious visual stimuli can be processed by human observers and modulate their behavior. This has been shown for masked prime stimuli that influence motor responses to subsequent target stimuli. Beyond this, masked stimuli can also affect participants' behavior when they are free to choose one of two response alternatives. This finding demonstrates that an apparently free-choice between alternative behaviors can be subject to influences that are outside of awareness. We report three experiments which exhibit that the temporal dynamic of free-choice priming effects corresponds to that of forced-choice priming effects. Forced-choice priming effects were relatively robust against variations of prime stimuli but sensitive to physical features of target stimuli. Free-choice priming effects, in contrast, depended largely on the stimulus-response compatibility of the prime. A simple accumulator model which accounts for forced-choice response priming can also explain free-choice priming effects by the assumption that unconscious stimuli can initiate motor responses when participants are engaged in a speeded choice-reaction time task. According to our analyses free-choice priming results from a response selection mechanism which integrates conscious and unconscious information from external, stimulus driven sources and also from internal sources.     

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.     

The Influence of Masked Stimuli on Response Selection: Evidence from a Semantic Categorization Task

Unconscious visual stimuli can be processed by human observers and influence their behaviour. A striking example is a phenomenon known as “free-choice priming,” where masked “prime” stimuli—of which participants are unaware—modulate which of two response alternatives they are likely to choose. Recent efforts to uncover the mechanisms underlying this intriguing effect have revealed that free-choice priming can emerge even in the absence of automatized stimulus-response (S-R) associations between masked primes and specific motor responses, indicating that free choices can be influenced by a masked prime’s meaning (Ocampo, 2015). It remains unknown, however, whether masked primes bias response selections because they are implicitly classified according to task instructions, or because spreading activation occurs within the prime's semantic network. To adjudicate between these two possibilities, participants in the present experiment categorised targets as either animals or people and selected which of two response alternatives they wanted to make following presentation of a free-choice target. Crucially, while implicit classifications could proceed during processing of both animal and person masked primes, only animal primes could trigger spreading activation within their semantic network. This manipulation modulated free-choice priming; only masked animal primes influenced response selections to free-choice targets. This result indicates that an automatic spreading activation mechanism might underlie a masked prime’s ability to influence free-choice responses.     

Negative stimulus–response compatibility observed with a briefly displayed image of a hand

Manual responses can be primed by viewing an image of a hand. The left–right identity of the viewed hand reflexively facilitates responses of the hand that corresponds to the identity. Previous research also suggests that when the response activation is triggered by an arrow, which is backward-masked and presented briefly, the activation manifests itself in the negative priming effect. The present study showed that response activation, which is produced by an identity of a briefly presented image of a hand, can be similarly associated with a negative priming effect. However, in contrast to the previously reported negative priming effects, the hand stimuli produced negative priming even when the hand was not backward-masked and did not contain task-relevant information. The study supports the view that the automatic inhibition of motor activation triggered by briefly viewed objects is a general and basic functional principle in exogenous motor control processes.     

Finger posing primes number comprehension

Canonical finger postures, as used in counting, activate number knowledge, but the exact mechanism for this priming effect is unclear. Here we dissociated effects of visual versus motor priming of number concepts. In Experiment 1, participants were exposed either to pictures of canonical finger postures (visual priming) or actively produced the same finger postures (motor priming) and then used foot responses to rapidly classify auditory numbers (targets) as smaller or larger than 5. Classification times revealed that manually adopted but not visually perceived postures primed magnitude classifications. Experiment 2 obtained motor priming of number processing through finger postures also with vocal responses. Priming only occurred through canonical and not through non-canonical finger postures. Together, these results provide clear evidence for motor priming of number knowledge. Relative contributions of vision and action for embodied numerical cognition and the importance of canonicity of postures are discussed.     

Mechanisms of visual threat detection in specific phobia

People with anxiety or stress-related disorders attend differently to threat-relevant compared with non-threat stimuli, yet the temporal mechanisms of differential allocation of attention are not well understood. We investigated two independent mechanisms of temporal processing of visual threat by comparing spider-phobic and non-fearful participants using a rapid serial visual presentation task. Consistent with prior literature, spider phobics, but not non-fearful controls, displayed threat-specific facilitated detection of spider stimuli relative to negative stimuli and neutral stimuli. Further, signal detection analyses revealed that facilitated threat detection in spider-phobic participants was driven by greater sensitivity to threat stimulus features and a trend towards a lower threshold for detecting spider stimuli. However, phobic participants did not display reliably slowed temporal disengagement from threat-relevant stimuli. These findings advance our understanding of threat feature processing that might contribute to the onset and maintenance of symptoms in specific phobia and disorders that involve visual threat information more generally.     

Unintentional processing of motivational valence

Recent motivational affective priming studies (Moors & De Houwer, 2001; Moors, De Houwer, & Eelen, 2004) showed that primes that indicate success on a goal-inducing task facilitate positive target responses whereas primes that indicate failure on that task facilitate negative target responses. In the current studies, we examined whether these priming effects depend on consciously intentional processing of the motivational valence of the primes. In Experiment 1, the outcome of success or failure was presented not only immediately before the target (i.e., the prime) but also a second time after the target response. This should encourage participants to ignore the prime. In Experiment 2, participants were asked to respond to the targets within 600 ms after target onset. As a result, participants had little opportunity to process the motivational prime valence in a consciously intentional way. Nevertheless, strong affective priming effects were found in both studies. These results provide additional support for the claim that motivational valence can be processed without the conscious intention to do so.     

But what about the Empress of Racnoss? The allocation of attention to spiders and Doctor Who in a visual search task is predicted by fear and expertise

If there is a spider in the room, then the spider phobic in your group is most likely to point it out to you. This phenomenon is believed to arise because our attentional systems are hardwired to attend to threat in our environment, and, to a spider phobic, spiders are threatening. However, an alternative explanation is simply that attention is quickly drawn to the stimulus of most personal relevance in the environment. Our research examined whether positive stimuli with no biological or evolutionary relevance could be allocated preferential attention. We compared attention to pictures of spiders with pictures from the TV program Doctor Who, for people who varied in both their love of Doctor Who and their fear of spiders. We found a double dissociation: interference from spider and Doctor-Who-related images in a visual search task was predicted by spider fear and Doctor Who expertise, respectively. As such, allocation of attention reflected the personal relevance of the images rather than their threat content. The attentional system believed to have a causal role in anxiety disorders is therefore likely to be a general system that responds not to threat but to stimulus relevance; hence, nonevolutionary images, such as those from Doctor Who, captured attention as quickly as fear-relevant spider images. Where this leaves the Empress of Racnoss, we are unsure.     

Inference revision processing in adults with and without aphasia

Processing abilities in aphasia, and the nature of processing breakdowns, were the focuses of this investigation. Individuals with either fluent or nonfluent aphasia, plus a control group, participated in a cross-modal lexical priming task designed to elicit priming effects when activation of inference interpretations occurred. Comprehension of inferences was measured by responses to four types of questions that related to the inferences. Results indicated that both the control group, as well as the nonfluent aphasia group, activated the intended meaning of the stimuli whereas the fluent aphasics did not. Comprehension of the inferences was best demonstrated by control participants, nonfluent aphasic participants, and fluent aphasic participants, in that order.     

Negative stimulus-response compatibility observed with a briefly displayed image of a hand

Manual responses can be primed by viewing an image of a hand. The left-right identity of the viewed hand reflexively facilitates responses of the hand that corresponds to the identity. Previous research also suggests that when the response activation is triggered by an arrow, which is backward-masked and presented briefly, the activation manifests itself in the negative priming effect. The present study showed that response activation, which is produced by an identity of a briefly presented image of a hand, can be similarly associated with a negative priming effect. However, in contrast to the previously reported negative priming effects, the hand stimuli produced negative priming even when the hand was not backward-masked and did not contain task-relevant information. The study supports the view that the automatic inhibition of motor activation triggered by briefly viewed objects is a general and basic functional principle in exogenous motor control processes.     

What you cannot see can help you: the effect of exposure to unreportable stimuli on approach behavior

We examined effects of exposure to unreportable images of spiders on approach towards a tarantula. Pretests revealed awareness of the stimuli was at chance. Participants high or low (top and bottom 15%) on fear of spiders were randomly assigned to receive computer-generated exposure to unreportable pictures of spiders or outdoor scenes. They then engaged in a Behavioral Approach Task (BAT) with a live tarantula. Non-fearful participants completed more BAT items than spider-fearful individuals. Additionally, as predicted, a significant interaction (F(1,48)=5.12, p<.03) between fear of spiders and stimulus demonstrated that spider-fearful participants exposed to spiders completed more BAT items than spider-fearful participants exposed to control stimuli (but not as many as non-fearful participants). The findings support the hypothesis that exposure to unreportable feared stimuli promotes approach towards the feared object. Future research and clinical implications were discussed.     

Unconscious integration of pointing relation between two masked arrows

In the present study, by using a briefly masked prime display paradigm, we investigated whether the pointing relation (same or different) between two unconsciously perceived arrows in the prime could be processed. Since only motor response priming can reflect unconscious processing of two arrows’ pointing-direction relation (i.e., a relational integration), we could distinguish the motor response priming from the visual priming in this study which in other studies were not separated. We also manipulated the prime-to-target stimulus onset asynchronies (SOA) by using a 70?ms and a 180?ms SOA. In this experiment, two masked arrow signs pointing in the same or different directions (> > or > <) were simultaneously presented in the prime, followed by two arrow symbols also pointing in the same or different directions in the target. The participants were asked to decide whether the two arrows in the target were pointing in the same or different directions. The results did not show any visual priming effect, but did show that the unconsciously perceived pointing relation in the prime elicited a positive motor response priming effect in RT under the 70?ms SOA condition, and a negative motor response priming effect in accuracy under the 180?ms SOA condition. The results were discussed in terms of self-motor-inhibition (or mask-triggered inhibition) and attention mechanisms. Overall, this study indicated that the pointing relation between the two subliminal arrows in the prime could influence the subsequent responses to the target and suggested that people can integrate unconsciously perceived information.