Abstract
In order to investigate the interactions between non-spatial selective attention, awareness and emotion processing, we carried out an ERP study using a backward masking paradigm, in which angry, fearful, happy, and neutral facial expressions were presented, while participants attempted to detect the presence of one or the other category of facial expressions in the different experimental blocks. ERP results showed that negative emotions enhanced an early N170 response over temporal-occipital leads in both masked and unmasked conditions, independently of selective attention. A later effect arising at the P2 was linked to awareness. Finally, selective attention was found to affect the N2 and N3 components over occipito-parietal leads. Our findings reveal that (i) the initial processing of facial expressions arises prior to attention and awareness; (ii) attention and awareness give rise to temporally distinct periods of activation independently of the type of emotion with only a partial degree of overlap; and (iii) selective attention appears to be influenced by the emotional nature of the stimuli, which in turn impinges on unconscious processing at a very early stage. This study confirms previous reports that negative facial expressions can be processed rapidly, in absence of visual awareness and independently of selective attention. On the other hand, attention and awareness may operate in a synergistic way, depending on task demand.
Highlights
In the two last decades, many studies have focused on conscious and unconscious processing of emotional stimuli
Our study reveals that facial expressions can be processed without awareness and independently of whether participants are engaged in an attempt to detect a specific emotion
It has been shown that both emotional faces and awareness can affect the amplitude (Balconi and Lucchiari, 2007) and latency (Balconi and Mazza, 2009) of the N2, while threatening stimuli appear to enhance the N170 (Pegna et al, 2008, 2011)
Summary
In the two last decades, many studies have focused on conscious and unconscious processing of emotional stimuli (for reviews, see Lindquist et al, 2012; Pourtois et al, 2013). Despite the discrepancies between these two studies regarding the location of the effects (possibly due to the use of different reference electrodes), these observations reveal that negative (fearful) emotional expressions are differentiated early in the course of visual information processing, and that this remains true even when the stimuli are not consciously detected. Such findings corroborate the existence of a rapid, preattentive process, in which negative emotional stimuli initiate attentional capture more effectively than positive or neutral ones (Öhman et al, 2001; Vuilleumier, 2005; Maratos, 2011)
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