Fear conditioning to subliminal fear relevant and non fear relevant stimuli

A growing body of evidence suggests that conscious visual awareness is not a prerequisite for human fear learning. For instance, humans can learn to be fearful of subliminal fear relevant images--images depicting stimuli thought to have been fear relevant in our evolutionary context, such as snakes, spiders, and angry human faces. Such stimuli could have a privileged status in relation to manipulations used to suppress usually salient images from awareness, possibly due to the existence of a designated sub-cortical 'fear module'. Here we assess this proposition, and find it wanting. We use binocular masking to suppress awareness of images of snakes and wallabies (particularly cute, non-threatening marsupials). We find that subliminal presentations of both classes of image can induce differential fear conditioning. These data show that learning, as indexed by fear conditioning, is neither contingent on conscious visual awareness nor on subliminal conditional stimuli being fear relevant.

A Happy Face Advantage With Male Caucasian Faces

Happy faces are categorized faster as “happy” than angry faces as “angry,” the happy face advantage. Here, we show across three experiments that the size of the happy face advantage for male Caucasian faces varies as a function of the other faces they are presented with. A happy face advantage was present if the male Caucasian faces were presented among male African American faces, but absent if the same faces were presented among female faces, Caucasian or African American. The modulation of the happy face advantage for male Caucasian faces was observed even if the female Caucasian/male African American faces had neutral expressions. This difference in the happy face advantage for a constant set of faces as a function of the other faces presented indicates that it does not reflect on a stimulus-dependent bottom-up process but on the evaluation of the expressive faces within a specific context.

Emotional expressions preferentially elicit implicit evaluations of faces also varying in race or age

Both facial cues of group membership (race, age, and sex) and emotional expressions can elicit implicit evaluations to guide subsequent social behavior. There is, however, little research addressing whether group membership cues or emotional expressions are more influential in the formation of implicit evaluations of faces when both cues are simultaneously present. The current study aimed to determine this. Emotional expressions but not race or age cues elicited implicit evaluations in a series of affective priming tasks with emotional Caucasian and African faces (Experiments 1 and 2) and young and old faces (Experiment 3). Spontaneous evaluations of group membership cues of race and age only occurred when those cues were task relevant, suggesting the preferential influence of emotional expressions in the formation of implicit evaluations of others when cues of race or age are not salient. Implications for implicit prejudice, face perception, and person construal are discussed.

Different faces in the crowd: a happiness superiority effect for schematic faces in heterogeneous backgrounds

Recently, D.V. Becker, Anderson, Mortensen, Neufeld, and Neel (2011) proposed recommendations to avoid methodological confounds in visual search studies using emotional photographic faces. These confounds were argued to cause the frequently observed Anger Superiority Effect (ASE), the faster detection of angry than happy expressions, and conceal a true Happiness Superiority Effect (HSE). In Experiment 1, we applied these recommendations (for the first time) to visual search among schematic faces that previously had consistently yielded a robust ASE. Contrary to the prevailing literature, but consistent with D.V. Becker et al. (2011), we observed a HSE with schematic faces. The HSE with schematic faces was replicated in Experiments 2 and 3 using a similar method in discrimination tasks rather than fixed target searches. Experiment 4 isolated background heterogeneity as the key determinant leading to the HSE.

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.