A tale of two negatives: Differential memory modulation by threat-related facial expressions.

Facial expressions serve as cues that encourage viewers to learn about their immediate environment. In studies assessing the influence of emotional cues on behavior, fearful and angry faces are often combined into one category, such as “threat-related,” because they share similar emotional valence and arousal properties. However, these expressions convey different information to the viewer. Fearful faces indicate the increased probability of a threat, whereas angry expressions embody a certain and direct threat. This conceptualization predicts that a fearful face should facilitate processing of the environment to gather information to disambiguate the threat. Here, we tested whether fearful faces facilitated processing of neutral information presented in close temporal proximity to the faces. In Experiment 1, we demonstrated that, compared with neutral faces, fearful faces enhanced memory for neutral words presented in the experimental context, whereas angry faces did not. In Experiment 2, we directly compared the effects of fearful and angry faces on subsequent memory for emotional faces versus neutral words. We replicated the findings of Experiment 1 and extended them by showing that participants remembered more faces from the angry face condition relative to the fear condition, consistent with the notion that anger differs from fear in that it directs attention toward the angry individual. Because these effects cannot be attributed to differences in arousal or valence processing, we suggest they are best understood in terms of differences in the predictive information conveyed by fearful and angry facial expressions. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Visual Awareness and the Detection of Fearful Faces.

A commonly held view is that emotional stimuli are processed independently of awareness. Here, the authors parametrically varied the duration of a fearful face target stimulus that was backward masked by a neutral face. The authors evaluated awareness by characterizing behavioral performance using receiver operating characteristic curves from signal detection theory. Their main finding was that no universal objective awareness threshold exists for fear perception. Although several subjects displayed a behavioral pattern consistent with previous reports (i.e., targets masked at 33 ms), a considerable percentage of their subjects (64%) were capable of reliably detecting 33-ms targets. Their findings suggest that considerable information is available even in briefly presented stimuli (possibly as short as 17 ms) to support masked fear detection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masked fearful faces modulate the orienting of covert spatial attention.

Dot probe studies indicate that masked fearful faces modulate spatial attention. However, without a baseline to compare congruent and incongruent reaction times, it is unclear which aspect(s) of attention (orienting or disengagement) is affected. Additionally, backward masking studies commonly use a neutral face as the mask stimulus. This method results in greater perceptual inconsistencies for fearful as opposed to neutral faces. Therefore, it is currently unclear whether the effects of backward masked fearful faces are due to the fearful nature of the face or perceptual inconsistencies. Equally unclear, is whether this spatial attention effect is due to orienting or disengagement. Two modified dot probe experiments with neutral (closed mouth in Experiment 1) and smiling (open mouth in Experiment 2) masks were used to determine the role of perceptual inconsistencies in mediating the spatial attention effects elicited by masked fearful faces. The results indicate that masked fearful faces modulate the orienting of spatial attention, and it appears that this effect is due to the fearful nature of the face rather than perceptual inconsistencies between the initial faces and masks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fearful faces but not fearful eyes alone delay attention disengagement in 7-month-old infants.

Adult-like attentional biases toward fearful faces can be observed in 7-month-old infants. It is possible, however, that infants merely allocate attention to simple features such as enlarged fearful eyes. In the present study, 7-month-old infants (n = 15) were first shown individual emotional faces to determine their visual scanning patterns of the expressions. Second, an overlap task was used to examine the latency of attention disengagement from centrally presented faces. In both tasks, the stimuli were fearful, happy, and neutral facial expressions, and a neutral face with fearful eyes. Eye-tracking data from the first task showed that infants scanned the eyes more than other regions of the face; however, there were no differences in scanning patterns across expressions. In the overlap task, infants were slower in disengaging attention from fearful as compared to happy and neutral faces and also to neutral faces with fearful eyes. Together, these results provide evidence that threat-related stimuli tend to hold attention preferentially in 7-month-old infants and that the effect does not reflect a simple response to differentially salient eyes in fearful faces. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Unconscious anxiety": Phobic responses to masked stimuli.

Tested the hypothesis that an unconscious preattentive perceptual analysis of phobic stimuli is sufficient to elicit human fear responses. Selected snake- and spider-fearful Ss, as well as normal controls, were exposed to pictures of snakes, spiders, flowers, and mushrooms. A separate forced-choice recognition experiment established backward masking conditions that effectively precluded recognition of experimental stimuli both for fearful and nonfearful Ss. In the main experiment, these conditions were used to compare skin conductance responses (SCRs) to masked and nonmasked phobic and control pictures among fearful and nonfearful Ss. In support of the hypotheses, snake- and spider-fearful Ss showed elevated SCRs to snake and spider pictures as compared with neutral pictures and with responses of the nonfearful Ss under both masking conditions. Ratings of valence, arousal, and dominance indicated that the fearful Ss felt more negative, more aroused, and less dominant in relation to both masked and nonmasked phobic stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Affective learning increases sensitivity to graded emotional faces.

How does the affective significance of emotional faces affect perceptual decisions? We manipulated affective significance by pairing 100% fearful faces with aversive electrical stimulation and hypothesized that increasing the significance of a stimulus via its prior history would lead to enhanced processing. After fear conditioning, participants viewed graded emotional faces that ranged from neutral to fearful. Faces were shown either in a color that was previously paired with shock or a color not paired with shock during conditioning. Increases in the frequency of "fearful" responses for faces shown in the shock-paired color were most robust for faces at intermediate intensity levels (40-60% fearful). Psychometric fits to the data revealed significant increased sensitivity for shock-paired relative to unpaired faces. Thus, despite identical physical features for shock-paired and unpaired stimuli (aside from the color, which was counterbalanced), more frequent (and faster) "fearful" responses were made when participants viewed affectively significant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical brain regions engaged by masked emotional faces in adolescents and adults: An fMRI study.

Face-emotion processing has shown signs of developmental change during adolescence. Functional magnetic resonance imaging (fMRI) was used on 10 adolescents and 10 adults to contrast brain regions engaged by a masked emotional-face task (viewing a fixation cross and a series of masked happy and masked fearful faces), while blood oxygen level dependent signal was monitored by a 1.5-T MRI scanner. Brain regions differentially engaged in the 2 age groups were mapped by using statistical parametric mapping. Summed across groups, the contrast of masked face versus fixation-cross viewing generated activations in occipital-temporal regions previously activated in passive face-viewing tasks. Adolescents showed higher maxima for activations in posterior association cortex for 3 of the 4 statistical contrasts. Adolescents and adults differed in the degree to which posterior hemisphere brain areas were engaged by viewing masked facial displays of emotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric perception of emotional valence from facial expressions.

The authors previously reported that normal subjects are better at discriminating happy from neutral faces when the happy face is located to the viewer's right of the neutral face; conversely, discrimination of sad from neutral faces is better when the sad face is shown to the left, supporting a role for the left hemisphere in processing positive valence and for the right hemisphere in processing negative valence. Here, the authors extend this same task to subjects with unilateral cerebral damage (31 right, 28 left). Subjects with right damage performed worse when discriminating sad faces shown on the left, consistent with the prior findings. However, subjects with either left or right damage actually performed superior to normal controls when discriminating happy faces shown on the left. The authors suggest that perception of negative valence relies preferentially on the right hemisphere, whereas perception of positive valence relies on both left and right hemispheres. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual marking and facial affect: Can an emotional face be ignored?

Previewing a set of distractors allows them to be ignored in a subsequent visual search task (Watson & Humphreys, 1997). Seven experiments investigated whether this preview benefit can be obtained with emotional faces, and whether negative and positive facial expressions differ in the extent to which they can be ignored. Experiments 1–5 examined the preview benefit with neutral, negative, and positive previewed faces. These results showed that a partial preview benefit occurs with face stimuli, but that the valence of the previewed faces has little impact. Experiments 6 and 7 examined the time course of the preview benefit with valenced faces. These showed that negative faces were more difficult to ignore than positive faces, but only at short preview durations. Furthermore, a full preview benefit was not obtained with face stimuli even when the preview duration was extended up to 3 s. The findings are discussed in terms of the processes underlying the preview benefit, their ecological sensitivity, and the role of emotional valence in attentional capture and guidance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

MerMade: an oligodeoxyribonucleotide synthesizer for high throughput oligonucleotide production in dual 96-well plates

This study was conducted to examine the relationship between baseline salivary cortisol (CORT) levels and selective attention for displays of angry faces. Selective attention was investigated using a pictorial emotional Stroop task, comparing colournaming-speed of angry and neutral faces. The task was assessed in supraliminal (unmasked) and subliminal (masked) conditions to 28 non-clinical subjects (14 male and 14 female). Repeated measures analysis of variance revealed a significant interaction between median split CORT levels (low vs. high) and masked face valence (angry vs. neutral). The latter effect was mainly due to significant facilitation in the high CORT subject-group; these subjects seemed to allocate their attention away from the masked angry face. A relation between baseline CORT levels and fast withdrawal behavior is suggested.     

No effect of inversion on attentional and affective processing of facial expressions.

The decrease in recognition performance after face inversion has been taken to suggest that faces are processed holistically. Three experiments, 1 with schematic and 2 with photographic faces, were conducted to assess whether face inversion also affected visual search for and implicit evaluation of facial expressions of emotion. The 3 visual search experiments yielded the same differences in detection speed between different facial expressions of emotion for upright and inverted faces. Threat superiority effects, faster detection of angry than of happy faces among neutral background faces, were evident in 2 experiments. Face inversion did not affect explicit or implicit evaluation of face stimuli as assessed with verbal ratings and affective priming. Happy faces were evaluated as more positive than angry, sad, or fearful/scheming ones regardless of orientation. Taken together these results seem to suggest that the processing of facial expressions of emotion is not impaired if holistic processing is disrupted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conscious and unconscious emotional learning in the human amygdala

If subjects are shown an angry face as a target visual stimulus for less than forty milliseconds and are then immediately shown an expressionless mask, these subjects report seeing the mask but not the target. However, an aversively conditioned masked target can elicit an emotional response from subjects without being consciously perceived. Here we study the mechanism of this unconsciously mediated emotional learning. We measured neural activity in volunteer subjects who were presented with two angry faces, one of which, through previous classical conditioning, was associated with a burst of white noise. In half of the trials, the subjects' awareness of the angry faces was prevented by backward masking with a neutral face. A significant neural response was elicited in the right, but not left, amygdala to masked presentations of the conditioned angry face. Unmasked presentations of the same face produced enhanced neural activity in the left, but not right, amygdala. Our results indicate that, first, the human amygdala can discriminate between stimuli solely on the basis of their acquired behavioural significance, and second, this response is lateralized according to the subjects' level of awareness of the stimuli.     

A differential neural response in the human amygdala to fearful and happy facial expressions

The amygdala is thought to play a crucial role in emotional and social behaviour. Animal studies implicate the amygdala in both fear conditioning and face perception. In humans, lesions of the amygdala can lead to selective deficits in the recognition of fearful facial expressions and impaired fear conditioning, and direct electrical stimulation evokes fearful emotional responses. Here we report direct in vivo evidence of a differential neural response in the human amygdala to facial expressions of fear and happiness. Positron-emission tomography (PET) measures of neural activity were acquired while subjects viewed photographs of fearful or happy faces, varying systematically in emotional intensity. The neuronal response in the left amygdala was significantly greater to fearful as opposed to happy expressions. Furthermore, this response showed a significant interaction with the intensity of emotion (increasing with increasing fearfulness, decreasing with increasing happiness). The findings provide direct evidence that the human amygdala is engaged in processing the emotional salience of faces, with a specificity of response to fearful facial expressions.     

The effect of age on memory for emotional faces.

Prior studies of emotion suggest that young adults should have enhanced memory for negative faces and that this enhancement should be reduced in older adults. Several studies have not shown these effects but were conducted with procedures different from those used with other emotional stimuli. In this study, researchers examined age differences in recognition of faces with emotional or neutral expressions, using trial-unique stimuli, as is typically done with other types of emotional stimuli. They also assessed the influence of personality traits and mood on memory. Enhanced recognition for negative faces was found in young adults but not in older adults. Recognition of faces was not influenced by mood or personality traits in young adults, but lower levels of extraversion and better emotional sensitivity predicted better negative face memory in older adults. These results suggest that negative expressions enhance memory for faces in young adults, as negative valence enhances memory for words and scenes. This enhancement is absent in older adults, but memory for emotional faces is modulated in older adults by personality traits that are relevant to emotional processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anxiety and sensitivity to gaze direction in emotionally expressive faces.

This study investigated the role of neutral, happy, fearful, and angry facial expressions in enhancing orienting to the direction of eye gaze. Photographs of faces with either direct or averted gaze were presented. A target letter (T or L) appeared unpredictably to the left or the right of the face, either 300 ms or 700 ms after gaze direction changed. Response times were faster in congruent conditions (i.e., when the eyes gazed toward the target) relative to incongruent conditions (when the eyes gazed away from the target letter). Facial expression did influence reaction times, but these effects were qualified by individual differences in self-reported anxiety. High trait-anxious participants showed an enhanced orienting to the eye gaze of faces with fearful expressions relative to all other expressions. In contrast, when the eyes stared straight ahead, trait anxiety was associated with slower responding when the facial expressions depicted anger. Thus, in anxiety-prone people attention is more likely to be held by an expression of anger, whereas attention is guided more potently by fearful facial expressions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A subcortical pathway to the right amygdala mediating "unseen" fear

Neuroimaging studies have shown differential amygdala responses to masked ("unseen") emotional stimuli. How visual signals related to such unseen stimuli access the amygdala is unknown. A possible pathway, involving the superior colliculus and pulvinar, is suggested by observations of patients with striate cortex lesions who show preserved abilities to localize and discriminate visual stimuli that are not consciously perceived ("blindsight"). We used measures of right amygdala neural activity acquired from volunteer subjects viewing masked fear-conditioned faces to determine whether a colliculo-pulvinar pathway was engaged during processing of these unseen target stimuli. Increased connectivity between right amygdala, pulvinar, and superior colliculus was evident when fear-conditioned faces were unseen rather than seen. Right amygdala connectivity with fusiform and orbitofrontal cortices decreased in the same condition. By contrast, the left amygdala, whose activity did not discriminate seen and unseen fear-conditioned targets, showed no masking-dependent changes in connectivity with superior colliculus or pulvinar. These results suggest that a subcortical pathway to the right amygdala, via midbrain and thalamus, provides a route for processing behaviorally relevant unseen visual events in parallel to a cortical route necessary for conscious identification.     

Fearful expressions gain preferential access to awareness during continuous flash suppression.

Rapid evaluation of ecologically relevant stimuli may lead to their preferential access to awareness. Continuous flash suppression allows assessment of affective processing under conditions in which stimuli have been rendered invisible due to the strongly suppressive nature of dynamic noise relative to static images. The authors investigated whether fearful expressions emerge from suppression into awareness more quickly than images of neutral or happy expressions. Fearful faces were consistently detected faster than neutral or happy faces. Responses to inverted faces were slower than those to upright faces but showed the same effect of emotional expression, suggesting that some key feature or features in the inverted faces remained salient. When using stimuli solely representing the eyes, a similar bias for detecting fear emerged, implicating the importance of information from the eyes in the preconscious processing of fear expressions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Positive and negative emotion enhances the processing of famous faces in a semantic judgment task.

Previous work has consistently reported a facilitatory influence of positive emotion in face recognition (e.g., D’Argembeau, Van der Linden, Comblain, & Etienne, 2003). However, these reports asked participants to make recognition judgments in response to faces, and it is unknown whether emotional valence may influence other stages of processing, such as at the level of semantics. Furthermore, other evidence suggests that negative rather than positive emotion facilitates higher level judgments when processing nonfacial stimuli (e.g., Mickley & Kensinger, 2008), and it is possible that negative emotion also influences latter stages of face processing. The present study addressed this issue, examining the influence of emotional valence while participants made semantic judgments in response to a set of famous faces. Eye movements were monitored while participants performed this task, and analyses revealed a reduction in information extraction for the faces of liked and disliked celebrities compared with those of emotionally neutral celebrities. Thus, in contrast to work using familiarity judgments, both positive and negative emotion facilitated processing in this semantic-based task. This pattern of findings is discussed in relation to current models of face processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear detection and visual awareness in perceiving bodily expressions.

Many research reports have concluded that emotional information can be processed without observers being aware of it. The case for perception without awareness has almost always been made with the use of facial expressions. In view of the similarities between facial and bodily expressions for rapid perception and communication of emotional signals, we conjectured that perception of bodily expressions may also not necessarily require visual awareness. Our study investigates the role of visual awareness in the perception of bodily expressions using a backward masking technique in combination with confidence ratings on a trial-by-trial basis. Participants had to detect in three separate experiments masked fearful, angry and happy bodily expressions among masked neutral bodily actions as distractors and subsequently the participants had to indicate their confidence. The onset between target and mask (Stimulus Onset Asynchrony, SOA) varied from ?50 to +133 ms. Sensitivity measurements (d-prime) as well as the confidence of the participants showed that the bodies could be detected reliably in all SOA conditions. In an important finding, a lack of covariance was observed between the objective and subjective measurements when the participants had to detect fearful bodily expressions, yet this was not the case when participants had to detect happy or angry bodily expressions. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Structural resemblance to emotional expressions predicts evaluation of emotionally neutral faces.

[Correction Notice: An erratum for this article was reported in Vol 9(4) of Emotion (see record 2009-11528-009). In this article a symbol was incorrectly omitted from Figure 1, part C. To see the complete article with the corrected figure, please go to http://dx.doi.org/10.1037/a0014681.] People make trait inferences based on facial appearance despite little evidence that these inferences accurately reflect personality. The authors tested the hypothesis that these inferences are driven in part by structural resemblance to emotional expressions. The authors first had participants judge emotionally neutral faces on a set of trait dimensions. The authors then submitted the face images to a Bayesian network classifier trained to detect emotional expressions. By using a classifier, the authors can show that neutral faces perceived to possess various personality traits contain objective resemblance to emotional expression. In general, neutral faces that are perceived to have positive valence resemble happiness, faces that are perceived to have negative valence resemble disgust and fear, and faces that are perceived to be threatening resemble anger. These results support the idea that trait inferences are in part the result of an overgeneralization of emotion recognition systems. Under this hypothesis, emotion recognition systems, which typically extract accurate information about a person's emotional state, are engaged during the perception of neutral faces that bear subtle resemblance to emotional expressions. These emotions could then be misattributed as traits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)