In two traditional attentional blink (AB) experiments, we addressed the extent to which emo-tionally relevant stimuli modulate temporal attention in the healthy population. We hypothesised that both fearful and happy facial expressions, as T2 targets, would modulate the AB more than neutral facial expressions (H1). We also hypothesised that dynamic facial expressions would mod-ulate the AB more than static facial expressions (H2). Results to our first experiment confirmed both of these hypotheses. In a second experiment, we ruled out the alternative explanation that
the strong modulation of the AB for dynamic stimuli we observed might have been due to the sole motion contained in the stimuli we presented, and not to the facial motion portrayed by the face targets.
The AB phenomenon reflects the competition of several processes early in the processing stream.
The resulting behavioural curve expresses a very particular view of this competition: the evolution over time of the performance on T2 task upon correct response on T1 task. This curve, studied as a whole, does not allow to perceive the underlying competing processes. If properly described, however, some understanding of the underlying processes can be gathered by focusing on ”aspects of interest”. The novel methodology we used (Cousineau et al., 2006) allowed to disentangle four of such aspects, which we interpreted as reflecting the activation and competition of a number of processes during three periods of time (Figure 5.2, panel a).
Of particular interest, we showed that each of these three periods may reflect the effects of distinct processes involved in the competition between T1 and T2. We propose the following scenario: From onset up to 200 msec after the onset of T1, a process appraises low-level features of the occurring event, and the degree to which upcoming stimuli can interfere with the ongoing processing. We predict that the perceptual system will attempt to prevent this new stimulus from disturbing the ongoing processing by activatingaparticular mechanism (i.e. the ”closure of an attentional gate”, Kessler et al., 2005; Sergent et al., 2005; Hommel et al., 2006). The ”stronger” this second stimulus, the earlier in time will occur this interfering mechanism. In later stages of the competition, however, a stimulus eliciting a strong bottom-up activation (e.g., an emotional stimulus) will benefit from the support of higher-level processes, which will alleviate the weakening interfering mechanism, and support its reportability.
Interestingly, a similar distinction between ”early” and ”late” pre-attentive evaluative processes has emerged in an attempt to explain discrepant results in studies addressing emotional modulation of spatial attention. In dot-probe paradigms in particular, researchers are concerned with the stimuli onset asynchrony (SOA) between the cue and the target: short and long SOAs yielding to very different results. According to the hypervigilance-avoidance hypothesis, patients suffering from social anxiety would be more prone to attend to threatening information during the early stages (SOA up to 300 msec) of the processing stream, and would shift their attention away from such information in later stages (SOA over 400 msec) of the processing (see Amir et al., 1998; Santesso et al., 2008).
Our results also go in line with the increasing electrophysiological literature showing that even unreported T2 targets in AB experiments are processed at a semantic level (Luck et al., 1996;
Shapiro, Raymond, & Arnell, 1997; Vogel et al., 1998; Marois et al., 2004; Sergent et al., 2005;
Dehaene et al., 2006; Hommel et al., 2006). In particular, we showed that emotional stimuli, regardless of their valence, are being appraised very early in the processing stream. Results of this appraisal influenced the unfolding of the AB curve by either interfering or supporting their further processing, depending on the current stage of processing of T1 targets.
Taken together, our results add to the literature questioning the usefulness for the concept of a dedicated fear module. According to the proponents of this hypothesis ( ¨Ohman & Mineka, 2001; Mineka & ¨Ohman, 2002; Wiens et al., 2004), evolutionary pressure would have shaped our perceptual system with a dedicated module to quickly detect, and attend to threat-related material in the environment. Our results, and others (Tipples et al., 2002; Lipp et al., 2004;
Brosch & Sharma, 2005; Flykt et al., 2007; E. Fox et al., 2007; Brosch et al., 2007, in press), show that the perceptual system generally favors important information, and is not tuned to process one particular emotion. These results support appraisal theories of emotion in general, and the component process model in particular, by pointing at common evaluative mechanisms to all emotions. The fear module hypothesis, like basic emotion models in general, does not account for the details of the processing of emotional stimuli. In contrast, the component process model allows researchers to build more precise hypotheses concerning the mechanisms involved in emotional processing.
Our results naturally invite new challenges.
Computations. We proposed detailed descriptions of the early processes appraising upcoming stimuli. AB-like experiments can only provide indirect evidence for such claims, and our results need to be investigated further to grasp the content of the computations performed.
Automaticity. We did not address the extent to which these early appraisals are automatic (i.e.
immune from top-down influences), and future work could manipulate motivational or task con-texts.
Inter-individual differences. An increasing literature addresses inter-individual differences of per-ceptual systems. Two tracks are of particular interest. First, one study showed that temporal attention varies along at least three dissociable dimensions: efficacy, latency, and precision (Vul, Nieuwenstein, & Kanwisher, 2008). From one moment to the next, attention selection can for in-stance be more or less diffuse, and precision more or less spred out over time. Second, a few studies address inter-individual differences in attentional sensitivity (Pessoa et al., 2005; Szczepanowski &
Pessoa, 2007; Roesch et al., in revision, , see also next chapter), separating subjective awareness
(i.e. what the participants report having perceived) from objective awareness (i.e. their actual performance). These two tracks are complementary (as the former can be used to explain the latter), and future research should take these points into consideration.
Psychophysics of emotion: the
QUEST for emotional perception
Reproduced from: Roesch, E.B., Sander, D., Mumenthaler, C., Kerzel, D., Scherer, K.R. (in revision). Psychophysics of emotion: the QUEST for emotional perception. Journal of Vision.
Abstract: To investigate the mechanisms involved in automatic processing of facial expressions, we used the QUEST procedure to measure the display durations needed to make a gender decision on emotional faces portraying fearful, happy, or neutral facial expressions. In line with predictions of appraisal theories of emotion, our results showed greater processing priority of emotional stimuli regardless of their valence. Whereas all experimental conditions led to an averaged threshold of about 50 msec, fearful and happy facial expressions led to significantly less variability in the responses than neutral faces. Results suggest that attention may have been automatically drawn by the emotion portrayed by face targets, yielding more informative perceptions and less variable responses. The temporal resolution of the perceptual system (expressed by the thresholds) and the processing priority of the stimuli (expressed by the variability in the responses) may influence subjective and objective awareness, respectively.