ANXIETY AND AFFECTIVE CONTEXT MODULATE AWARENESS THRESHOLDS

Threat awareness is central to anxiety phenomenology. Previous studies have investigated anxious observers' ability to discriminate between different emotions using liminal or subliminal stimuli. Here, we asked whether a stimulus is more likely to access conscious perception in anxious individuals when it is threatening relative to when it is not. Crucially, the stimuli emotional contents were task-irrelevant. Anxious individuals required shorter exposure times to become aware of masked stimuli, irrespective of stimulus valence. However, whereas threat-related stimuli required lower exposure times in highthan in low anxiety individuals irrespective of stimulus context, positive stimuli required lower exposures only when presented among threatening stimuli. Our findings suggest a prominent role for affective context in anxious individuals' conscious perception of visual stimuli. Biases in automatic, preattentive processing of threat play a prominent role in etiology and maintenance of anxiety disorders. Information-processing models of fear suggest an early threat detection mechanism typically associated with the amygdala automatically assesses emotional valence of incoming information. According to these models, this mechanism is more sensitive in anxious than in non-anxious individuals, resulting in greater unconscious perception of threat, as well as enhanced attentional priority for threat in anxious individuals (see Bar-Haim et al., 2007 for review). Our objective in the present study was to investigate whether threat-related information may have privileged access to anxious subjects' awareness. As attention is often conceived as the gateway to conscious perception, enhanced attention to threat in anxiety should imply that these stimuli thrust more readily into the awareness of anxious individuals relative to non-anxious individuals. However, competing accounts such as the hypervigilance-avoidance hypothesis (e.g., Mathews, 1990) suggest that despite enhanced initial encoding of potential threat, avoidance of such stimuli aimed at reducing anxious mood states immediately follows, preventing elaborate evaluation processes typically occurring in non-anxious individuals. Thus, whether conscious awareness of threatening stimuli has privileged access to anxious individuals' awareness remains an open question. When addressing this issue, it is important to clarify whether one refers to awareness of the stimulus emotional content or to awareness of some other properties of the emotional stimulus. In the former case, one may ask whether observers are better at discriminating fearful faces from neutral ones than happy faces from neutral ones, for instance, and emotion is therefore task relevant. In the latter case, one may ask whether observers are better at discriminating a word from a non-word when the word happens to be threatening than when it happens to be neutral or positive, and emotion is therefore task irrelevant. These are fundamentally different questions: when emotion is task relevant, one probes subjects' ability to detect the presence of a given emotion relative to other emotions. When emotion is task irrelevant, one probes whether the valence of an object makes it easier to detect or distinguish from other object categories. Studies aimed at measuring anxiety-related individual differences in perception of emotional valence have typically relied on signal detection (SDT, Green & Swets, 1966) methods, using masks to limit exposure to the critical stimuli. Importantly, stimulus valence was task relevant. Anxious subjects were typically found not show higher perceptual sensitivity for threat than for positive stimuli, or to differ from non-anxious subjects in sensitivity, but exhibited a more liberal criterion. By contrast, studies in which emotion was task irrelevant compared perception of emotional stimuli only in the general population and reported higher detection rates for negative versus positive words, suggesting that preventing negative words from reaching awareness is more difficult. Similar studies focusing on anxiety-related individual differences have not been reported. In the present study we investigate whether threat-related information is privileged in awareness of anxious relative to non-anxious individuals when emotion is task-irrelevant. We could not use SDT for two reasons. First, in order to assess false alarms separately for each emotion category, SDT requires adopting a blocked design with regard to emotional valence. In a mixed design a false alarm is not emotion-specific, precluding the separate calculation of sensitivity and criterion for each emotion category. Yet, with blocked designs, one cannot be confident that emotion is task irrelevant because emotion is necessarily confounded with response. Second, SDT requires use of fixed SOAs. However, previous studies aimed at investigating perception thresholds for emotional stimuli in the general population have revealed that emotion-related differences in perceptual sensitivity vary as a function of the SOA used (e.g., Milders, Logan & Sahraie, 2007). Thus, using a fixed exposure may mask potential differences between emotions. We therefore designed a procedure that allows comparison of thresholds between anxious and non-anxious individuals for different expressions of emotion, as described below.