The impact of emotional stressors on distractor filtering

Human beings constantly deal with an enormous amount of information that cannot be processed at once. Given the limited cognitive resources available for the processing of incoming information, visual selective attention has the role to differentiate between competing stimuli in order to facilitate the processing of stimuli that are relevant for adaptive behaviours. From an evolutionary perspective, stimuli with emotional content, in particular those signalling danger or threat, are very powerful in attracting and holding attention even if they are task-irrelevant. Moreover, emotional stimuli get higher processing priority compared with other competing stimuli and their access to further processing and conscious perception is thought to be automatic, at least when sufficient cognitive resources are available. Therefore, avoiding emotional stimuli, especially those with negative content, requires a conspicuous amount of resources that, if engaged for a prolonged period of time in a highly demanding cognitive task, they can undergo depletion, and eventually lead to the mental fatigue phenomenon. We propose that the amount of resources specifically dedicated to selective attention are also limited, and that they can be depleted specifically, and possibly independently, from the resources available for other cognitive mechanisms. This work was planned in order to directly explore this possibility, assuming that the crucial resources necessary to overcome the impact of irrelevant emotional distractors are also involved in attentional processing, and – more specifically – in the filtering of distracting visual information. We expected that by heavily engaging these inhibitory mechanisms, providing conditions of heavy and persistent distraction, we would observe phenomena suggesting that they were being depleted during the course of the experimental session (i.e. one-hour session). In a series of visual search experiments, young adult participants had to discriminate a target stimulus, while ignoring a task-irrelevant distractor that could be present in a portion of trials. According to the aim of our research, in order to increase, on the one hand, the attentional load and, on the other, the need to filter out distracting information, task-irrelevant stimuli with emotional content were introduced prior to each visual search trial. I then measured performance to evaluate the overall impact of emotional stimuli, revealing that while the onset of all emotional stimuli affected attentional deployment in the subsequent trial, such impact was different according to the valence of the stimuli involved. Analysing the efficiency of distractor filtering processes over the experimental session, I observed changes in performance suggesting that the attentional resources specifically involved during the inhibition of distractors in the visual search task could indeed be depleted. By this new approach, in this series of studies I offered new evidence relative to the depletion of cognitive resources specific associated with selective attention. I demonstrated that these domain-specific resources can be depleted in a relatively short period of time (i.e., one-hour session). Moreover, I highlighted how emotional activation can either enhance or impair cognitive performance depending on the emotional valence of the stimuli involved, with negative emotions leading to detrimental effects and positive emotions leading to restorative effects on cognitive resources. I also provided evidence on the fact that under condition of high load on attentional processing, the active engagement of top-down behavioural control may limit, or even abolish, the detrimental effects of negative emotional stimuli.