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Emotion  2005 the American Psychological Association  2005, Vol. 5, No. 2, 243–247; 1528-3542/05/$12.00 DOI: 10.1037/1528-3542.5.2.243

Visual Awareness and the Detection of Fearful Faces - Luiz Pessoa, Brown University; Shruti Japee and Leslie G. Ungerleider, National Institute of Mental Health

Overview - 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 behavioural 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.

In detail - Emotional stimuli, such as a picture of a fearful face or an aversive scene, are processed rapidly. For example, when viewing such pictures, subjects exhibit fast, involuntary, autonomic responses (Ohman, Esteves, & Soares, 1995). Under some conditions, the processing of emotional stimuli may proceed when the stimuli are outside the focus of attention (Vuilleumier, Armony, Driver, & Dolan, 2001). Consistent with the view that the stimuli are processed pre-attentively, the detection of threat-related stimuli (e.g., a snake) is associated with relatively flat search slopes in visual search tasks (Ohman, Flykt, & Esteves, 2001). Many investigators have proposed that not only is the processing of emotional stimuli somewhat independent of attention but that it can take place without reaching conscious awareness. Evidence for this view comes from studies showing both skin conductance and neuroimaging responses to briefly presented and masked stimuli that subjects were apparently unaware of (Morris, Ohman, & Dolan, 1998; Ohman et al., 1995; Whalen et al., 1998). Taken together, the view has emerged that emotional (especially negative) stimuli are processed in a largely automatic fashion, which is independent of attention and awareness.