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.     

Attention for emotional faces under restricted awareness revisited: Do emotional faces automatically attract attention?

Theoretical models of attention for affective information have assigned a special status to the cognitive processing of emotional facial expressions. One specific claim in this regard is that emotional faces automatically attract visual attention. In three experiments, the authors investigated attentional cueing by angry, happy, and neutral facial expressions that were presented under conditions of limited awareness. In these experiments, facial expressions were presented in a masked (14 ms or 34 ms, masked by a neutral face) and unmasked fashion (34 ms or 100 ms). Compared with trials containing neutral cues, delayed responding was found on trials with emotional cues in the unmasked, 100-ms condition, suggesting stronger allocation of cognitive resources to emotional faces. However, in both masked and unmasked conditions, the hypothesized cueing of visual attention to the location of emotional facial expression was not found. In contrary, attentional cueing by emotional faces was less strong compared with neutral faces in the unmasked, 100-ms condition. These data suggest that briefly presented emotional faces influence cognitive processing but do not automatically capture visual attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Awareness of faces is modulated by their emotional meaning.

A central question in perception is how stimuli are selected for access to awareness. This study investigated the impact of emotional meaning on detection of faces using the attention blink paradigm. Experiment 1 showed that fearful faces were detected more frequently than neutral faces, and Experiment 2 revealed preferential detection of fearful faces compared with happy faces. To rule out image artifacts as a cause for these results, Experiment 3 manipulated the emotional meaning of neutral faces through fear conditioning and showed a selective increase in detection of conditioned faces. These results extend previous reports of preferential detection of emotional words or schematic objects and suggest that fear conditioning can modulate detection of formerly neutral stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional requirements in visual detection and identification: Evidence from the attentional blink.

Perception of the 2nd of 2 targets (T1 and T2) is impaired if the lag between them is short (0–500 ms). The authors used this attentional blink (AB) to index attentional requirements in detection and identification tasks, with or without backward masking of T2, in 2 stimulus domains (line orientation, coherent motion). With masking, the AB occurred because T2 was masked during the attentional dwell time created by T1 processing (Experiments 1, 2, and 3). Without masking, an AB occurred only in identification because during the attentional dwell time. T2 decayed to a level that could support simple detection but not complex identification. However, an AB occurred also in detection if T2 was sufficiently degraded (Experiment 4). The authors drew 2 major conclusions: (a) Attention is required in both identification and detection, and (b) 2 factors contribute to the AB, masking of T2 while attention is focused on T1 and decay of the T2 trace while unattended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional conditioning to masked stimuli: Expectancies for aversive outcomes following nonrecognized fear-relevant stimuli.

The role of conscious awareness in human Pavlovian conditioning was examined in 2 experiments using masked fear-relevant (snakes and spiders; Experiments 1 and 2) and fear-irrelevant (flowers and mushrooms; Experiment 1) pictures as conditioned stimuli, a mild electric shock as the unconditioned stimulus, and skin conductance responses as the primary dependent variable. The conditioned stimuli were presented briefly (30 ms) and were effectively masked by an immediately following masking stimulus. Experiment 1 demonstrated nonconscious conditioning to fear-relevant but not to fear-irrelevant stimuli. Even though the participants could not recognize the stimuli in Experiment 2, they differentiated between masked stimuli predicting and not predicting shocks in expectancy ratings. However, expectancy ratings were not related to the conditioned autonomic response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Murder, she wrote: Enhanced sensitivity to negative word valence.

Enhanced sensitivity to information of negative (compared to positive) valence has an adaptive value, for example, by expediting the correct choice of avoidance behavior. However, previous evidence for such enhanced sensitivity has been inconclusive. Here we report a clear advantage for negative over positive words in categorizing them as emotional. In 3 experiments, participants classified briefly presented (33 ms or 22 ms) masked words as emotional or neutral. Categorization accuracy and valence-detection sensitivity were both higher for negative than for positive words. The results were not due to differences between emotion categories in either lexical frequency, extremeness of valence ratings, or arousal. These results conclusively establish enhanced sensitivity for negative over positive words, supporting the hypothesis that negative stimuli enjoy preferential access to perceptual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The locus of interference in the perception of simultaneous stimuli.

In 3 experiments with 48 college students (18–33 yrs old), performance on well-practiced target detection tasks, both auditory and visual, was little influenced by the number of simultaneous nontargets, but suffered if simultaneous targets were detected separately. It is suggested that only targets need pass through a limited-capacity system leading to awareness (and hence availability for report); nontargets can be identified and rejected by earlier parallel, unconscious processes. Since nontarget words can be rejected on the basis of meaning, stimuli must be fully identified before the limited-capacity system. More generally, performance decrements due to divided attention are usually marked whenever simultaneous stimuli (psychophysical, verbal) must be identified separately and independently; under these circumstances all stimuli must pass through the limited-capacity system to awareness. (74 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in valence modulation of face-selective m170 response.

Magnetoencephalography was used to examine the effect of individual differences on the temporal dynamics of emotional face processing by grouping subjects based on their ability to detect masked valence-laden stimuli. Receiver operating characteristic curves and a nonparametric sensitivity measure were used to categorize subjects into those that could and could not reliably detect briefly presented fearful faces that were backward-masked by neutral faces. Results showed that, in a cluster of face-responsive sensors, the strength of the M170 response was modulated by valence only when subjects could reliably detect the masked fearful faces. Source localization of the M170 peak using synthetic aperture magnetometry identified sources in face processing areas such as right middle occipital gyrus and left fusiform gyrus that showed the valence effect for those target durations at which subjects were sensitive to the fearful stimulus. Subjects who were better able to detect fearful faces also showed higher trait anxiety levels. These results suggest that individual differences between subjects, such as trait anxiety levels and sensitivity to fearful stimuli, may be an important factor to consider when studying emotion processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the role of individual items in recognition memory and metacognition: Challenges for signal detection theory.

The authors tested the role of individual items in recognition memory using a forced-choice paradigm with face stimuli. They constructed distractor stimuli using morphing procedures that were similar to two parent faces and then compared a studied morph against an unstudied morph that was similar to two studied parents. The similarity of the parent faces was carefully balanced so that the choosing rates for the studied and unstudied morphs were approximately equal. Despite being equally likely to choose the studied and the unstudied morph, participants were systematically more confident when choosing the studied morph. This result is incompatible with Gaussian signal detection theory, even with unequal variances for targets and distractors. The authors propose an extension of an extant sampling model, SimSample, which provides a qualitative and quantitative account of the confidence and recognition dissociation. The results suggest that observers make contact with individual items when making recognition judgments with faces and that the structure of the sampling and decision process naturally leads to this dissociation of confidence and recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic priming and repetition priming from masked words: Evidence for a center-surround attentional mechanism in perceptual recognition.

Two lexical decision experiments compared semantic and repetition priming by masked words. Experiment 1 established prime–mask stimulus onset asynchronies (SOAs) with presence–absence detection judgments. Primes presented at detection-threshold SOAs produced equal facilitation for repeated and semantically related targets: 26 ms and 24 ms. Experiment 2 established SOAs with semantic judgments. Primes presented at 70% of the semantic-threshold SOA to mimic the exposure conditions of Experiment 1 produced slightly greater facilitation for repeated targets but a tendency toward inhibition for semantically related targets: 38 ms and –6 ms. These results confirm the D. Dagenbach et al (see record 1990-00392-001) report that strategies induced by threshold-setting tasks can influence masked priming. In addition, Experiment 2 suggests a mechanism for retrieving weakly activated semantic codes into consciousness that relies on the center-surround principle to enhance activation of sought-for codes and to inhibit related codes stored nearby in the semantic network. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in startle reactivity during the perception of angry and fearful faces.

Emotion researchers often categorize angry and fearful face stimuli as "negative" or "threatening". Perception of fear and anger, however, appears to be mediated by dissociable neural circuitries and often elicit distinguishable behavioral responses. The authors sought to elucidate whether viewing anger and fear expressions produce dissociable psychophysiological responses (i.e., the startle reflex). The results of two experiments using different facial stimulus sets (representing anger, fear, neutral, and happy) indicated that viewing anger was associated with a significantly heightened startle response (p     

The detection of fear-relevant stimuli: Are guns noticed as quickly as snakes?

Potentially dangerous stimuli are important contenders for the capture of visual-spatial attention, and it has been suggested that an evolved fear module is preferentially activated by stimuli that are fear relevant in a phylogenetic sense (e.g., snakes, spiders, angry faces). In this study, a visual search task was used to test this hypothesis by directly contrasting phylogenetically (snakes) and ontogenetically (guns) fear-relevant stimuli. Results showed that the modern threat was detected as efficiently as the more ancient threat. Thus, both guns and snakes attracted attention more effectively than neutral stimuli (flowers, mushrooms, and toasters). These results support a threat superiority effect but not one that is preferentially accessed by threat-related stimuli of phylogenetic origin. The results are consistent with the view that faster detection of threat in visual search tasks may be more accurately characterized as relevance superiority effects rather than as threat superiority effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Attentional Dynamics of Masked Detection.

A dichoptic masking procedure was used to test whether the mask-dependent cuing effects found in luminance detection by P. L. Smith (2000a) were due to integration masking or interruption masking. Attentional cuing enhanced detection sensitivity (d') when stimuli were backwardly masked with either dichoptic or monoptic masks, whereas no cuing effect was found with unmasked stimuli, implying the mask dependencies were due to interruption of stimulus processing in visual cortex by the mask. The effect is predicted by a gated diffusion process model in which masks interrupt stimulus processing and attention controls the flow of information to a sequential-sampling decision mechanism. The model correctly predicts different patterns of performance for detection and discrimination and cuing effects in simple reaction time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional mechanisms in simple visual detection: A speed–accuracy trade-off analysis.

Recent spatial cuing studies have shown that detection sensitivity can be increased by the allocation of attention. This increase has been attributed to one of two mechanisms: signal enhancement or uncertainty reduction. Signal enhancement is an increase in the signal-to-noise ratio at the cued location; uncertainty reduction is a reduction in the uncertainty associated with the location of the target. In displays with low uncertainty, cuing effects are typically found only if targets are backwardly masked. This phenomenon is known as the mask-dependent cuing effect. This effect was investigated in four experiments using the response signal paradigm, which controlled for speed–accuracy tradeoffs. For unmasked targets, cues failed to improve detection accuracy when uncertainty was absent (Experiment 1), but large cuing effects were obtained when uncertainty was present (Experiment 2). For masked targets, stronger cuing effects were obtained with a backward pattern mask (Experiment 3) than with a simultaneous noise mask (Experiment 4). We conclude that the cuing effects in simple detection with well-localized targets are due to a dynamic signal enhancement mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

To look or not to look: An eye movement study of hypervigilance during change detection in high and low spider fearful students.

Previous eye movement studies of attentional bias in spider fear reported inconsistent results with respect to early attentional capture, suggesting that overt attentional capture only reliably occurs under specific circumstances. In addition, none of these studies explored covert attention. The present study examined attentional bias in spider phobia using a change detection paradigm that was expected to provide good conditions for documenting attentional capture. In contrast to our expectations, eye movement data showed that all participants' first fixations were fastest on general negative targets, whereas participants' first fixations on spider targets were slower in the spider fearful than in the nonfearful group. In addition, spider fearful participants made more nontarget fixations before fixating on a spider target than did nonfearful participants. Thus, we found that participants' overt attention was more quickly focused on general negative targets, whereas covert attentional processes enabled initial avoidance of fear-relevant (i.e. spider) stimuli. The present findings have important implications for research on attention and fear as they indicate that fearful individuals are not characterized by static attentional orienting toward threat but, under certain conditions, may avert attention from threat automatically. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dissociating local and global levels of perceptuo-motor control in masked priming.

[Correction Notice: An erratum for this article was reported in Vol 33(3) of Journal of Experimental Psychology: Human Perception and Performance (see record 2007-07213-006). Figure 5 was inadvertently duplicated in the production process and was incorrectly substituted in place of the original Figure 6 submitted by the authors. The correct figure and caption that should have appeared for Figure 6 are listed in the erratum.] Masked prime stimuli presented near the threshold of conscious awareness affect responses to subsequent targets. The direction of these priming effects depends on the interval between masked prime and target. With short intervals, benefits for compatible trials (primes and targets mapped to the same response) and costs for incompatible trials are observed. This pattern reverses with longer intervals. We argue (a) that these effects reflect the initial activation and subsequent self-inhibition of the primed response, and the corresponding inhibition and subsequent disinhibition of the nonprimed response, and (b) that they are generated at dissociable local (within response channels) and global (between channels) levels of motor control. In two experiments, global-level priming effects were modulated by changing the number of response alternatives, whereas local-level effects remained unaffected. These experiments suggest that low-level motor control mechanisms can be successfully decomposed into separable subcomponents, operating at different levels within the motor system. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Playing chess unconsciously.

Expertise in a certain stimulus domain enhances perceptual capabilities. In the present article, the authors investigate whether expertise improves perceptual processing to an extent that allows complex visual stimuli to bias behavior unconsciously. Expert chess players judged whether a target chess configuration entailed a checking configuration. These displays were preceded by masked prime configurations that either represented a checking or a nonchecking configuration. Chess experts, but not novice chess players, revealed a subliminal response priming effect, that is, faster responding when prime and target displays were congruent (both checking or both nonchecking) rather than incongruent. Priming generalized to displays that were not used as targets, ruling out simple repetition priming effects. Thus, chess experts were able to judge unconsciously presented chess configurations as checking or nonchecking. A 2nd experiment demonstrated that experts' priming does not occur for simpler but uncommon chess configurations. The authors conclude that long-term practice prompts the acquisition of visual memories of chess configurations with integrated form-location conjunctions. These perceptual chunks enable complex visual processing outside of conscious awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facial asymmetry: Perceptual awareness and lateral differences.

Normal subjects participated in four experiments designed to examine their level of awareness of facial asymmetry and the possible lateralization of this awareness. For centrally displayed faces and symmetrical chimeras, subjects considered the normal face and its mirror-image as highly similar, and the two composite chimeras as highly dissimilar (Exp. 1, N = 10), but were unable to decide if the asymmetrical displayed stimulus was a normal or a mirrored face (Exp. 2, N = 30) except for experimentally familiarized subjects. For laterally displayed faces and chimeras, same/different judgements about pairs of stimuli (Exp. 3, N = 12) and face/nonface judgements (Exp. 4, N = 36) were very difficult even for trained subjects, and there was evidence for an advantage of the right visual field/left cerebral hemisphere. This study suggests that there is an awareness of facial asymmetry but not of the lateral direction of this asymmetry, that this awareness depends more on the processing of facial features than on holistic characteristics, and that within-face redundancy is an important parameter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional and perceptual factors affecting the attentional blink for faces and objects.

When 2 different visual targets presented among different distracters in a rapid serial visual presentation (RSVP) are separated by 400 ms or less, detection and identification of the 2nd targets are reduced relative to longer time intervals. This phenomenon, termed the attentional blink (AB), is attributed to the temporary engagement of a limited-capacity attentional system by the 1st target, which reduces resources available for processing the 2nd target. Although AB has been reliably obtained with many stimulus types, it has not been found for faces (E. Awh et al., 2004). In the present study, the authors investigate the underpinnings of this immunity. Unveiling circumstances in which AB occurs within and across faces and other categories, the authors demonstrate that a multichannel model cannot account for the absence of AB effects on faces. The authors suggest instead that perceptual salience of the face within the distracters' series as well as the available resources determine whether or not faces are blinked in RSVP. (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)