Of hissing snakes and angry voices: human infants are differentially responsive to evolutionary fear-relevant sounds

Adult humans demonstrate differential processing of stimuli that were recurrent threats to safety and survival throughout evolutionary history. Recent studies suggest that differential processing of evolutionarily ancient threats occurs in human infants, leading to the proposal of an inborn mechanism for rapid identification of, and response to, evolutionary fear-relevant stimuli. The current study provides novel data in support of this proposal, showing for the first time that human infants differentially process evolutionary threats presented in the auditory modality. Sixty-one 9-month-olds listened to evolutionary fear-relevant, modern fear-relevant, and pleasant sounds, while their heart rate, startle, and visual orienting behaviours were measured. Infants demonstrated significantly enhanced heart rate deceleration, larger eye-blinks, and more visual orienting when listening to evolutionary fear-relevant sounds compared to sounds from the other two categories. These results support the proposal that human infants possess evolved mechanisms for the differential processing of a range of ancient environmental threats.

In search of the emotional face: anger versus happiness superiority in visual search

Previous research has provided inconsistent results regarding visual search for emotional faces, yielding evidence for either anger superiority (i.e., more efficient search for angry faces) or happiness superiority effects (i.e., more efficient search for happy faces), suggesting that these results do not reflect on emotional expression, but on emotion (un-)related low-level perceptual features. The present study investigated possible factors mediating anger/happiness superiority effects; specifically search strategy (fixed vs. variable target search; Experiment 1), stimulus choice (Nimstim database vs. Ekman & Friesen database; Experiments 1 and 2), and emotional intensity (Experiment 3 and 3a). Angry faces were found faster than happy faces regardless of search strategy using faces from the Nimstim database (Experiment 1). By contrast, a happiness superiority effect was evident in Experiment 2 when using faces from the Ekman and Friesen database. Experiment 3 employed angry, happy, and exuberant expressions (Nimstim database) and yielded anger and happiness superiority effects, respectively, highlighting the importance of the choice of stimulus materials. Ratings of the stimulus materials collected in Experiment 3a indicate that differences in perceived emotional intensity, pleasantness, or arousal do not account for differences in search efficiency. Across three studies, the current investigation indicates that prior reports of anger or happiness superiority effects in visual search are likely to reflect on low-level visual features associated with the stimulus materials used, rather than on emotion.

Responses to loud auditory stimuli indicate that movement-related activation builds up in anticipation of action

Previous research using a loud acoustic stimulus (LAS) to investigate motor preparation in reaction time (RT) tasks indicates that responses can be triggered well in advance of the presentation of an imperative stimulus (IS). This is intriguing given that high levels of response preparation cannot be maintained for long periods (≈ 200 ms). In the experiments reported here we sought to assess whether response-related activation increases gradually over time in simple RT tasks. In experiment 1, a LAS was presented at different times just prior to the presentation of the IS to probe the level of activation for the motor response. In experiment 2, the same LAS was presented at different times after the presentation of the IS. The results provide evidence that response-related activation does increase gradually in anticipation of the IS, but it remains stable for a short time after this event. The data display a pattern consistent with the response being triggering by the LAS, rather than a reaction to the IS.

Discrepant integration times for upright and inverted faces

Judgments of upright faces tend to be more rapid than judgments of inverted faces. This is consistent with encoding at different rates via discrepant mechanisms, or via a common mechanism that is more sensitive to upright input. However, to the best of our knowledge no previous study of facial coding speed has tried to equate sensitivity across the characteristics under investigation (eg emotional expression, facial gender, or facial orientation). Consequently we cannot tell whether different decision speeds result from mechanisms that accrue information at different rates, or because facial images can differ in the amount of information they make available. To address this, we examined temporal integration times, the times across which information is accrued toward a perceptual decision. We examined facial gender and emotional expressions. We first identified image pairs that could be differentiated on 80% of trials with protracted presentations (1 s). We then presented these images at a range of brief durations to determine how rapidly performance plateaued, which is indicative of integration time. For upright faces gender was associated with a protracted integration relative to expression judgments. This difference was eliminated by inversion, with both gender and expression judgments associated with a common, rapid, integration time. Overall, our data suggest that upright facial gender and expression are encoded via distinct processes and that inversion does not just result in impaired sensitivity. Rather, inversion caused gender judgments, which had been associated with a protracted integration, to become associated with a more rapid process.

The processing of invariant and variant face cues in the Garner Paradigm

Faces provide a complex source of information via invariant (e.g., race, sex and age) and variant (e.g., emotional expressions) cues. At present, it is not clear whether these different cues are processed separately or whether they interact. Using the Garner Paradigm, Experiment 1 confirmed that race, sex, and age cues affected the categorization of faces according to emotional expression whereas emotional expression had no effect on the categorization of faces by sex, age, or race. Experiment 2 used inverted faces and replicated this pattern of asymmetrical interference for race and age cues, but not for sex cues for which no interference on emotional expression categorization was observed. Experiment 3 confirmed this finding with a more stringently matched set of facial stimuli. Overall, this study shows that invariant cues interfere with the processing of emotional expressions. It indicates that the processing of invariant cues, but not of emotional expressions, is obligatory and that it precedes that of emotional expressions.

Electro-cortical implicit race bias does not vary with participants' race or sex

Earlier research found evidence for electro-cortical race bias towards black target faces in white American participants irrespective of the task relevance of race. The present study investigated whether an implicit race bias generalizes across cultural contexts and racial in- and out-groups. An Australian sample of 56 Chinese and Caucasian males and females completed four oddball tasks that required sex judgements for pictures of male and female Chinese and Caucasian posers. The nature of the background (across task) and of the deviant stimuli (within task) was fully counterbalanced. Event-related potentials (ERPs) to deviant stimuli recorded from three midline sites were quantified in terms of mean amplitude for four components: N1, P2, N2 and a late positive complex (LPC; 350-700 ms). Deviants that differed from the backgrounds in sex or race elicited enhanced LPC activity. These differences were not modulated by participant race or sex. The current results replicate earlier reports of effects of poser race relative to background race on the LPC component of the ERP waveform. In addition, they indicate that an implicit race bias occurs regardless of participant's or poser's race and is not confined to a particular cultural context.

The effects of arousal and valence on facial electromyographic asymmetry during blocked picture viewing

The effect of stimulus valence and arousal on facial electromyographic (EMG) asymmetry was investigated to inform the debate about two contrasting hypotheses of emotion: the right hemisphere dominance hypothesis and the valence hypothesis. EMG was recorded from the left and right corrugator and zygomaticus muscles while participants (N = 21) viewed blocks of negative and positive pictures that were high or low in arousal. Ratings of valence and arousal were taken before and after each of the four emotion blocks. Corrugator muscle activity yielded evidence for left hemi-face dominance during high and low arousal negative picture blocks whereas zygomaticus muscle activity yielded evidence for right hemi-face dominance during high arousal positive picture blocks, especially early during the picture sequence. This pattern of results is consistent with the valence hypothesis.

Competing for consciousness: prolonged mask exposure reduces object substitution masking

In object substitution masking (OSM) a sparse, temporally trailing 4-dot mask impairs target identification, even though it has different contours from, and does not spatially overlap with the target. Here, we demonstrate a previously unknown characteristic of OSM: Observers show reduced masking at prolonged (e.g., 640 ms) relative to intermediate mask durations (e.g., 240 ms). We propose that with prolonged exposure, the mask's visual representation is consolidated, which allows processing of the lingering target icon to be reinitiated, thereby improving performance. Our findings suggest that when the visual system is confronted with 2 temporally contiguous stimuli, although one may initially gain access to consciousness above the other, the "losing" stimulus is not irreversibly lost to awareness.

Delayed Reentrant Processing Impairs Visual Awareness

In object-substitution masking (OSM), a sparse, common-onset mask impairs perception of a target when the mask’s offset is later than the target’s offset and spatial attention is dispersed. OSM is thought to reflect the interaction of feed-forward and reentrant processes in the brain: Upon stimulus presentation, a low-resolution representation of the target and mask progresses from sensory to anterior brain regions, triggering reentrant processing to confirm stimulus identity. It is hypothesized that dispersing spatial attention prolongs the required reentrant iterations, increasing the likelihood that only the lingering mask stimulus will remain physically present and thus substitute for the target in consciousness. However, empirically, it remains unclear whether substitution stems from delayed feed-forward or reentrant processing. Here, we demonstrate that delayed reentrant processing causes OSM, by showing that a task tapping high-level brain regions involved in reentrant processing leads to a spatially attended target being replaced by the mask. Our results confirm a key role for reentrant processing in conscious perception.

Selective attention for masked and unmasked emotionally toned stimuli: effects of trait anxiety, state anxiety, and test order

We investigated selective attention for masked and unmasked, threat, and positively valenced words, in high trait anxious (HTA) and low trait anxious (LTA) individuals using the emotional Stroop colour-naming task. State anxiety was varied within participants through the threat of electric shock. To investigate whether the sequencing of the state anxiety manipulation affected colour-naming latencies, the ordering of the shock threat and shock safe conditions was counterbalanced across participants. The results indicated that the ordering of the state anxiety manipulation moderated masked and unmasked threat bias effects. Specifically, relative to LTA individuals, HTA individuals showed a threat interference effect, but this effect was limited to those who performed under the threat of shock in the later stages of the experiment. Irrespective of exposure mode and state anxiety status, all individuals showed interference for threat in the early stages of the experiment, relative to a threat facilitation effect in the later stages of the experiment. For the unmasked trials alone, the data also revealed a significant threat interference effect for the HTA group relative to the LTA group in the shock threat condition, and this effect was evident irrespective of shock threat order. The results are discussed with respect to the automatic nature of emotional processing in anxiety.

Modality-specific attentional startle modulation during continuous performance tasks: a brief time is sufficient

Attentional startle modulation has been found to be modality specific in continuous performance tasks (CPTs) and modality nonspecific in trial-structured tasks. Experiment 1 investigated whether attentional blink modulation in a CPT would change if a trial structure was imposed. Participants performed a visual CPT either continuously (CONT), or during brief periods of time signaled by a change in screen color with stimuli either presented all the time (MIXED) or only during the trial segments (DISC). Contrary to expectation, evidence for modality-specific attentional startle modulation-smaller acoustic startle during targets than during nontargets-was strongest in Groups MIXED and DISC. Experiment 2 confirmed that this pattern of results was present during the first stimulus of the task period in group DISC. This suggests that the continuous nature of a task is not critical in determining the attentional mechanisms engaged.

Is aversive learning a marker of risk for anxiety disorders in children?

Aversive conditioning and extinction were evaluated in children with anxiety disorders (n=23), at-risk for anxiety disorders (n=15), and controls (n=11). Participants underwent 16 trials of discriminative conditioning of two geometric figures, with (CS+) or without (CS-) an aversive tone (US), followed by 8 extinction trials (4 CS+, 4 CS-), and 8 extinction re-test trials averaging 2 weeks later. Skin conductance responses and verbal ratings of valence and arousal to the CS+/CS- stimuli were measured. Anxiety disordered children showed larger anticipatory and unconditional skin conductance responses across conditioning, and larger orienting and anticipatory skin conductance responses across extinction and extinction re-test, all to the CS+ and CS-, relative to controls. At-risk children showed larger unconditional responses during conditioning, larger orienting responses during the first block of extinction, and larger anticipatory responses during extinction re-test, all to the CS+ and CS-, relative to controls. Also, anxiety disordered children rated the CS+ as more unpleasant than the other groups. Elevated skin conductance responses to signals of threat (CS+) and signals of safety (CS-; CS+ during extinction) are discussed as features of manifestation of and risk for anxiety in children, compared to the specificity of valence judgments to the manifestation of anxiety.

Affect, attention, or anticipatory arousal? Human blink startle modulation in forward and backward affective conditioning

Affect modulates the blink startle reflex in the picture-viewing paradigm, however, the process responsible for reflex modulation during conditional stimuli (CSs) that have acquired valence through affective conditioning remains unclear. In Experiment 1, neutral shapes (CSs) and valenced or neutral pictures (USs) were paired in a forward (CS-->US) manner. Pleasantness ratings supported affective learning of positive and negative valence. Post-acquisition, blink reflexes were larger during the pleasant and unpleasant CSs than during the neutral CS. Rather than affect, attention or anticipatory arousal were suggested as sources of startle modulation. Experiment 2 confirmed that affective learning in the picture-picture paradigm was not affected by whether the CS preceded the US. Pleasantness ratings and affective priming revealed similar extents of affective learning following forward, backward or simultaneous pairings of CSs and USs. Experiment 3 utilized a backward conditioning procedure (US-->CS) to minimize effects of US anticipation. Again, blink reflexes were larger during CSs paired with valenced USs regardless of US valence implicating attention rather than anticipatory arousal or affect as the process modulating startle in this paradigm.

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.

Does emotion modulate the blink reflex in human conditioning? Startle potentiation during pleasant and unpleasant cues in the picture?picture paradigm

Emotional processes modulate the size of the eyeblink startle reflex in a picture-viewing paradigm, but it is unclear whether emotional processes are responsible for blink modulation in human conditioning. Experiment 1 involved an aversive differential conditioning phase followed by an extinction phase in which acoustic startle probes were presented during CS+, CS-, and intertrial intervals. Valence ratings and affective priming showed the CS+ was unpleasant postacquisition. Blink startle magnitude was larger during CS+ than during CS-. Experiment 2 used the same design in two groups trained with pleasant or unpleasant pictorial USs. Ratings and affective priming indicated that the CS+ had become pleasant or unpleasant in the respective group. Regardless of CS valence, blink startle was larger during CS+ than CS- in both groups. Thus, startle was not modulated by CS valence.

Automatic attention does not equal automatic fear: preferential attention without implicit valence

Theories of nonassociative fear acquisition hold that humans have an innate predisposition for some fears, such as fear of snakes and spiders. This predisposition may be mediated by an evolved fear module (Ohman & Mineka, 2001) that responds to basic perceptual features of threat stimuli by directing attention preferentially and generating an automatic fear response. Visual search and affective priming tasks were used to examine attentional processing and implicit evaluation of snake and spider pictures in participants with different explicit attitudes; controls (n = 25) and snake and spider experts (n = 23). Attentional processing and explicit evaluation were found to diverge; snakes and spiders were preferentially attended to by all participants; however, they were negative only for controls. Implicit evaluations of dangerous and nondangerous snakes and spiders, which have similar perceptual features, differed for expert participants, but not for controls. The authors suggest that although snakes and spiders are preferentially attended to, negative evaluations are not automatically elicited during this processing.

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.

Reaction time facilitation by acoustic task-irrelevant stimuli is not related to startle

Previous research has been interpreted to suggest that the startle reflex mediates the RT facilitation observed if intense, accessory acoustic stimuli are presented coinciding with the onset of a visual imperative stimulus in a forewarned simple RT task. The present research replicated this finding as well as the facilitation of startle observed during the imperative stimulus. It failed, however, to find any relationship between the size of the blink startle reflex elicited by the accessory acoustic stimuli, which differed in intensity and rise time, and RT or RT facilitation observed on trials with accessory acoustic stimuli. This finding suggests that the RT facilitation is not mediated by the startle reflex elicited by the accessory acoustic stimuli.

The effects of assessment type on verbal ratings of conditional stimulus valence and contingency judgments: implications for the extinction of evaluative learning

Recent research on causal learning found (a) that causal judgments reflect either the current predictive value of a conditional stimulus (CS) or an integration across the experimental contingencies used in the entire experiment and (b) that postexperimental judgments, rather than the CS's current predictive value, are likely to reflect this integration. In the current study, the authors examined whether verbal valence ratings were subject to similar integration. Assessments of stimulus valence and contingencies responded similarly to variations of reporting requirements, contingency reversal, and extinction, reflecting either current or integrated values. However, affective learning required more trials to reflect a contingency change than did contingency judgments. The integration of valence assessments across training and the fact that affective learning is slow to reflect contingency changes can provide an alternative interpretation for researchers' previous failures to find an effect of extinction training on verbal reports of CS valence.

The feasibility and outcome of clinic plus internet delivery of cognitive-behavior therapy for childhood anxiety

Seventy-two clinically anxious children, aged 7 to 14 years, were randomly allocated to clinic-based, cognitive-behavior therapy, the same treatment partially delivered via the Internet, or a wait-list control (WL). Children in the clinic and clinic-plus-Internet conditions showed significantly greater reductions in anxiety from pre- to posttreatment and were more likely to be free of their anxiety diagnoses, compared with the WL group. Improvements were maintained at 12-month follow-up for both therapy conditions, with minimal difference in outcomes between interventions. The Internet treatment content was highly acceptable to families, with minimal dropout and a high level of therapy compliance.