The Addition of Emotional Processing

In line with a number of previous studies using the Flanker task, the performance data in the current study were consistent with a significant interference effect during neutral and emo- tional Flanker tasks, with incongruent stimuli eliciting longer RTs than congruent ones (Alguacil et al., 2013; Chen et al., 2014; Ochsner et al., 2009). Further, whereas the emotional Flanker in- terference effect was larger than the neutral Flanker interference effect, participants showed comparable mean RTs on baseline and congruent trials of both the neutral and emotional ver- sions of the task. This pattern suggests that responses slowed significantly more when negative emotional stimuli flanked positive targets than when neutral cues served as distracting stimuli. Further, it is consistent with the idea that the addition of an emotional processing component to the Flanker task increases the cognitive control required to perform well (Chiew & Braver, 2011; Fenske & Eastwood, 2003).

In contrast, the addition of an emotional processing component to the Stroop task did not result in larger interference effects. In fact, the observed interference effects on the emotional Stroop task differed strikingly from those on all of the other three cognitive control tasks, with participants responding faster on incongruent than on congruent trials. In other words, nega- tively-valenced emotional information appeared to enhance processing rather than to interfere with it. Further, participants responded more quickly during trials across all conditions of the emotional Stroop task than they did on similar conditions of the neutral Stroop task. This pattern of performance suggests that the inclusion of emotional stimuli (positive and negative) in the emotional Stroop task enhanced response speed on the task as a whole. It also suggests that responding was further facilitated when participants were presented with negatively-valenced emotional words. Thus, the negatively-valenced emotional stimuli did not appear to interfere

with responding or increase cognitive control demands in the same way that the negative flank- ing information did in the emotional Flanker task. Moreover, the presence of emotional stimuli in the Stroop task actually appears to have enhanced the use of cognitive control.

The failure of an emotional overlay to increase interference during the Stroop task was surprising, given findings in previous studies (Algom, Chajut, & Lev, 2004; Estes & Adelman, 2008; Egner, Etkin, Gale, & Hirsch, 2008; Etkin, Egner, Peraza, Kandel, & Hirsch, 2006; Mac- Leod & MacDonald, 2000; Williams, Mathews, & MacLeod, 1996). However, characteristics of the study sample and of the emotional Stoop stimulus words may have played roles in the unex- pected pattern of task performance. For instance, previous studies showing that negative emo- tional information slows down responding have largely recruited clinical samples (i.e., adults with significant depression or anxiety). The current study, in contrast, focused on young adults drawn from a non-clinical, healthy population. In light of evidence that individual differences in anxiety and depression may modulate how emotion effects responding on cognitive control-type tasks (see review: Kanske, 2012), the absence of a clinical group may have contributed to the failure to elicit interference.

Additionally, differences between the words used in past and current emotional Stroop tasks may have influenced results in important ways. For example, Larsen, Mercer, and Balota (2006) reported that the often-replicated slowdown in color naming of emotional words may be due, in part, to lexical differences between the emotional and control words used in many stud- ies. In an effort to avoid such confounding of emotional and lexical effects, the current study matched neutral and emotional words based on multiple lexical characteristics in addition to the more standard matching on valence, arousal, and word length. Thus, it is possible that the facili- tation, rather than interference, found in the current study reflects a more valid estimation of the effect of emotional stimuli on color naming and cognitive control than those obtained in research

with stimuli that had not been as closely matched on their lexical features. Further research un- derstanding emotional Stroop performance with psychometrically sound tasks is warranted to better understand the effect of emotional stimuli on Stroop performance.

Although the discrepancy between the effects of emotional stimuli in the Flanker and Stroop tasks was unforeseen, it aligns with research suggesting that emotional stimuli may af- fect performance in different ways, depending on the way in which they are used in a task, as well as on their relevance to successful performance (see Figure 8; Kanske, 2012). Kanske (2012) argued that if the emotional stimuli are task-relevant, which means they are the stimuli that participants need to process and react to in order to solve the task, then emotion should speed up cognitive conflict processing rather than slow it down. If, however, emotional stimuli are task-irrelevant and serve merely as distracters or ancillary cues, the dual competition model proposed by Pessoa (2009) suggests they may instead impede cognitive conflict processing be- cause the cognitive resources needed are shared and diverted to negative emotional stimuli.

It could be argued that the emotional stimuli in the emotional Stroop tasks are task-rele- vant, in that emotional information is integrated into the target stimuli (MacLeod, 1991) and thus might be expected to enhance the exercise of cognitive control. The emotional Flanker task pre- sents a more complicated picture; although there are emotional stimuli that are task-relevant stimuli (i.e., positive target faces), there are also emotional task-irrelevant distracters (e.g., neg- ative flanking faces) that are spatially adjacent to the target and that could act to slow down re- sponding. The cognitive control task paradigms used in the current study incorporate emotion in different ways and yield different patterns of outcomes. These divergent outcomes across paradigms suggests that emotional cognitive control is not purely driven by the presence of emotional content, but that it also depends on the way in which an individual engages with the emotional content. If this is the case, tasks that vary the role of emotional information should be grouped together with caution. Further, it is possible that varied indices of emotional cognitive

control might differentially relate to the onset and maintenance of various mental health prob- lems; individual consideration of discrete task performance patterns could help to characterize and possibly inform treatment of the underlying cognitive biases that contribute to select mental health problems.