PERFILES DE OBSERVACIONES CLIMÁTICAS EN LA COSTA SURESTE A SUROESTE DE TENERIFE EN ENERO

The last section suggested that attentional resources can "spill over" to (emotion) processing (Pessoa et al., 2002). This fits with the aforementioned predications of perceptual load theory

(discussed in section 1.2 - Limits in facial social judgment), where for example, as in the many studies of perceptual load, interference, for instance by meaningful 3D distractor pictures on a name-

categorization task (e.g. fruits versus musical instruments) depends on the level of perceptual load (the number of letter-strings) in the task (Lavie et al., 2003).

One may think that the ability to attend to socially significant information such as faces would be an inherent property of our attentional system, and somewhat supporting this position is the observation that in contrast to the effects of perceptual load on objects, interference by famous distractor faces are unaffected by the level of perceptual load in a famous-name categorization task (pop stars versus statesmen) (Lavie et al., 2003). A possible interpretation for this result is that people are more susceptible to interference by distractor stimuli of social significance, such as famous faces. Such an interpretation is supported by the fact that interference and priming effects were created regardless of whether attention was fully engaged in a task of high perceptual load (Lavie et al., 2003). Although in contrast, long-term explicit recognition memory of distractor faces presented in the experiment, either famous or anonymous, did depend on the level of load in the relevant task, being no better than chance in tasks of high load (searching for a target letter among similar non-target letters) (Jenkins, Burton, & Ellis, 2002; Jenkins, Lavie, & Driver, 2005).

The results of the aforementioned behavioural studies are also supported by a relatively recent novel electrophysiological study. This study, employing perceptual load theory, explored the capacity of attention to prime (famous) faces on short-term repetition effects in event-related potentials (ERPs). The results revealed ERP repetition effects in terms of an N250r at occipito-temporal regions,

suggesting priming of face identification processes, which were unaffected by perceptual load. This study indicated that task-irrelevant face processing is relatively preserved under perceptual load, and

thus supports the notion of face specific attentional resources, at least for famous faces (Neumann & Schweinberger, 2008). This ERP accords with the outcomes described by a similar behavioural study by Jenkins and colleagues, although memory for faces, including immediate recognition, was affected by concurrent demands for (nonface) shape processing capacity at exposure in their study (Jenkins, Lavie, & Driver, 2003).

Given these coherent findings, can we conclude that face processing may be “modular” in the sense of proceeding independently of attention or in relying solely on face-specific processing resources (Jenkins et al., 2003)? Although some aspects of face-processing may depend upon face specific mechanisms, the boundary conditions on such claims should be cautiously considered due to the use of famous celebrity faces’ in these studies, which may skew our interpretations. Well-known and recognizable faces may access strong mental representations and thus require little attentional capacity or indeed be processed in an atypical fashion (Buttle & Raymond, 2003). For instance, the actual task of judging the positive or negative qualities of famous faces strongly modulates amygdala activation to those faces, but processes negative information less flexibly than positive information (Cunningham, Van Bavel, & Johnsen, 2008b).

What are we to make of this result that famous distracter faces are processed irrespective of the level of the perceptual load task? These observations seemingly aligns with some of the earlier neuropsychological studies, suggesting that facial visual stimuli have attentional priority, perhaps due to being stimuli of high social significance. However, there are studies showing that top-down effects such as attentional load may be effective in impacting the neural processing of emotional facial stimuli, which are also presumably stimuli of high social significance (Pessoa et al., 2002).

Consistent with the notion that task load was important in determining the extent of processing of the face stimuli, Pessoa and colleagues (Pessoa et al., 2002) revealed that differential amygdala responses to emotional facial expressions can be eliminated by high “perceptual load” (in an important riposte to the earlier work of Vuilleumier and colleagues (Vuilleumier et al., 2001a)). In this study, the authors suggested that the neural processing of facial emotional stimuli is not automatic and requires some degree of attention, similar to the processing of other stimulus categories. They claimed that the failure to modulate the processing of emotional stimuli by attention in prior studies was caused by a failure to fully engage attention by a competing task (although their study manipulations had slight differences to perceptual load tasks as they measured attended/unattended processing, rather than high/ low modulation of perception).

Pessoa and colleagues findings of differential amygdala responses to emotional facial

expressions under load have been complemented by similar findings that emotional influences from both facial expressions and other stimulus materials may be reduced under conditions of higher attentional load (Okon-Singer et al., 2007; Erthal et al., 2005). Moreover, also consistent with the perceptual load hypothesis (Lavie et al., 2003), other studies have indicated that amygdala activation is likely contingent on the unoccupied attentional resources for facial expressions and hence only

observed when attention is not fully consumed by a distracting task (Mitchell et al., 2007; Silvert et al., 2007). Both Mitchell et al and Silvert et al only found increased activation in the amygdala and

fusiform cortex under conditions of low attentional load for the main task, but not under conditions of high load (also see (Pessoa, 2005)).

A possible criticism to some of the results discussed in this section is that the elimination of emotion processing under high load may be because the distractor was not salient enough. As noted by Lavie, (Lavie, 1995) there is no “gold standard” for determining “high” perceptual load without being circular. However, even increasing the affective salience of a (threatening) face distractor (so that the influence of distractor intrusion was manipulated in addition to perceptual load) did not make them more resistant to modulation by attention (Yates, Ashwin, & Fox, 2010).

A number of studies have thus cast doubts on the tempting and appealing idea that the processing of facial expressions (conceding that many of the examples exploring this issue employ threat-related stimuli) is unconstrained (particularly in the amygdala) by the availability of attentional resources (that is, that amygdala activation can be affected by load). How these effects are mediated are unknown, although given that a complete suppression of amygdala responses to unattended faces may occur only when there are scarcely any attentional resources available for their processing (Pessoa, 2005), could mean that inattention or reduced perceptual capacity could make the emotional expression of faces with reduced attention more ambiguous, leading to undifferentiated amygdala activation (Whalen et al., 1998). This implies that when attention is reduced in facial expression processing, not only could amygdala activation be reduced, but amygdala responses could also gradually lose their specificity (Silvert et al., 2007).

Taken together, much of the neuroimaging results in this section suggest that emotional facial processing will be severely reduced if the perceptual load of an attended task exhausts capacity limits, where Lavie’s theoretical perceptual load framework (Lavie, 1995) provides an explanation for this conclusion.

The long-running debate over the of role selective attention in processing ‘‘special’’ status stimuli such as faces can lead one to discount the effects of other modulatory influences that may have a role, along with attention, in gating the processing of facial stimuli. For example, factors such as trait anxiety may affect attentional capacity and attentional control engendering selective biases which interact with facial processing. A more detailed discussion of how anxiety is related to emotion perception and its role in the allocation of attention is provided in the following section.