Neural Indices of Emotional Distraction
Emotional stimuli capture our attention. The preferential processing of emotional information is an adaptive mechanism that when relevant to our goal highlights potentially important aspects in the environment. However, when emotional information is task-irrelevant, their presence in the environment can trigger involuntary shifts in attention that cause detriments to performance. One challenge to investigating emotional distraction in the lab is how to objectively investigate the allocation of attention between different elements on the same stimulus display (e.g. between the task and the distractors). One neural measure that overcomes this issue is the Steady-State-Visual-Evoked-Potential (SSVEP). An SSVEP is the neural response of the visual cortex to a flickering stimulus and can be used as a measure of attentional resource allocation (Norcia, Appelbaum, Ales, Cottereau, & Rossion, 2015). In the past, emotional distraction has been studied using spatially separated tasks and distractors. The current thesis presents two experiments using SSVEPs to investigate emotional distraction in a superimposed design. Experiment 1 aimed to conceptually replicate Hindi Attar and colleagues (2010) who developed an SSVEP emotional distraction paradigm to examine attentional resource allocation between background task-irrelevant emotional distractors and a foreground dot-motion task. Participants viewed a stimulus display of moving, flickering dots, while positive or neutrally valanced distractors (or unidentifiable scrambles) were presented in the background of the task. SSVEPs were reduced in the presence of positive intact compared to neutral intact distractors suggesting that the presentation of task-irrelevant emotional stimuli in the same spatial location as a foreground task initiates an involuntary shift of attention away from the task. Unexpectedly, in both Experiments 1 and 2 valence differences were found in SSVEPs between positive and neutral scrambled images; this suggests that there are some perceptual differences between the stimulus sets (e.g. colour) contributing to the drop in SSVEP found for positive intact images. Importantly, in the SSVEP analysis significant valence x image type interactions were found, demonstrating that the drop for positive images was stronger for intact than scrambled image conditions, suggesting that a significant amount of the drop in SSVEP was driven by a difference in valence between the intact distractors. Behavioural results also suggest evidence for emotional distraction through reduced hit rate in the presence of positive intact images compared to neutral intact images in Experiment 1, and reduced detection sensitivity and response criterion for positive intact images in Experiment 2. Overall, the current thesis demonstrates support for the hypothesis that emotional information is more distracting than neutral information and provides a valuable starting point for the examination of emotion attention interactions when the task and distractors share the same location. Future studies could use SSVEPs to examine neural processing differences between emotional and neutral scrambled images.