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Emotional Stroop Task

The Emotional Stroop task is a variation of the original Stroop effect, created by John Ridley Stroop in 1935, in which reaction time is used to assess emotional responses to words. “For example, depressed participants will be slower to say the color of depressing words rather than non-depressing words. Non-clinical subjects have also been shown to name the color of an emotional word (e.g., "war", "cancer", "kill") slower than naming the color of a neutral word (e.g., "clock", "lift", "windy"). The classic Stroop effect creates a conflict between an incongruent color and word (the word "RED" in font color blue) but the emotional Stroop involves only emotional and neutral words—color does not affect slowing because it does not conflict with word meaning. In other words, studies show the same effects of slowing for emotional words relative to neutral even if all the words are black. Thus, the emotional Stroop does not involve an effect of conflict between a word meaning and a color of text, but rather appears to capture attention and slow response time due to the emotional relevance of the word for the individual.” (Original Article)

Due to such effects, it has been particularly useful to test individuals with psychological disorders. The target words contain information or stimuli that pertain to the individual’s disorder, such as the stimuli “spider” or “crawl” for individuals with a phobia of spiders, or “bullet” and “death” for veterans with posttraumatic stress disorder. The individual must then read through a list of neutral or emotionally salient words, and read aloud the color the word is printed in, not the word itself. Participants in both the original and emotional task are asked to ignore the words to the best of their ability, and simply focus on announcing the color of ink the word is printed in.

The task can be administered by computer or by hand-held cards. Various time-measurement devices can be used for the reaction time, although most modern researchers use computer equipment in order to get the most precise time possible. Stop watches have been used in past research and yield similar findings, however they are less accurate due to human error and reflexes.

Questions pertaining to the actual effects, reliability, and generalizability of the task (both between clinical diagnostic categories, and between healthy and clinically diagnosed samples) still remain. Despite both the original and emotional task tending to result in slowed reaction times, the mechanism by which the emotional Stroop task operates is unclear.

Neural Correlates
Certain areas of the brain are known to be activated for various attentional and emotional tasks, however the brain has not been obstensively observed during the emotional Stroop task. When negative or inconsistent colored-words appeared, the dorsolateral frontal lobe was activated, suggesting that this area is involved in maintaining selective in the presence of distracting information. Drawing selective attention away from negative emotional words stimulate activity in the bilateral occipito-temporal area, and decrease activation in the amygdala. This is specifically for the emotional Stroop task, as incongruent stimuli for the original Stroop task activated the left parietal area and decreased activity in the parahippocampal gyrus. This evidence suggests that the tasks are working with different areas of the brain, and thus, different aspects of selective attention.

Psychopathology
It is very important to note that the use of the emotional Stroop task for non-clinically diagnosed individuals yields very different results than the task for clinically diagnosed patients would. For this reason, individuals with mental illness or psychopathologies are discussed as a separate group here.

The emotional Stroop task has been tested on an array of patients with psychopathological disorders, and is a diagnostic tool for some, including depression, anxiety , eating disorders, phobias , and post-traumatic stress-disorder. It can also be used after treatment to determine if the disorder is still present. There would be no Stroop effect present if the disorder had been successfully treated.

Effects
Traditional Stroop tests and studies using Event-related potential suggest that the presence of a delay in reaction time as a response to emotionally salient words is caused by an attentional bias, which stems from the individuals ability to recognize emotionally salient words whether or not they have an emotional psychopathology. Even exposure to the words before the task itself does not disrupt the interference caused by the word during the task.

Although the emotional relevance of target words was thought to be the characteristic driving the effect, there has been debate about the cause of the emotional Stroop results. There have been instances in which slower reaction times have not occurred, despite obviously distracting salient stimuli. For example, one study finds that when there is no time pressure on participants to respond immediately, the effect disappears. This suggests that the task may be measuring the effects of time pressure which may bias attention toward negative stimuli, as opposed to measuring an actual difference in information-processing due to emotionally salient words. Carry-over effects may also occur when neutral and emotionally-salient words are presented together in the same block, covering the Stroop effect altogether.

Another issue is that negative emotional words tended to slow reaction times for a variety of information-processing tasks, however there was no difference in reaction time when negative and neutral words were displayed together in the same section of trials. This suggests that the delay in reaction time is due to a rationing of resources after the person perceives threatening information, rather than the original Stroop task effect of engaging automatic processes over controlled ones. Negative or threatening information is easier for humans to process because it is detected more quickly than neutral or positive information. This occurs whether or not it is particularly salient to the individual.

Some evidence has shown that state emotions may affect performance, for example in cases where people with social phobia are put in a high anxiety situation, however it appears that for the majority of cases the differences in performance are due to trait emotion, such as genuinely depressed individuals as opposed to those inducted into a negative mood. Stimuli that enhance the interference include state anxiety, as it draws attention to emotionally salient words in healthy participants, while increased time pressure encourages the effect for negative stimuli , meaning that participants will need more time to react to a stimulus if they are presented rapidly.

The effect has been attributed to attentional bias by some, however others suggest a connectionist model, schema theory , network theory , prioritization model , and parallel distributed processing models. Causation of the Stroop effect remains unclear for all versions of the task, as may vary depending on characteristics of the population being tested.

Reliability
The reliability of the interference effects has not yet been strongly supported in all areas that use the task, however the reliability may depend on how one measures the task. Researchers have found that test re-test reliability, or repeatability for the traditional and emotional Stroop task tends to be high when response times are used as the measure, but low when measured by difference scores. The reaction times may also differ depending on how the stimuli are sequenced, allowing for fast or slow effects to arise. This means that sometimes the interference appears as a longer delay in reaction time than other test trials, however when considering trials relative to other trials during that session, they are not significantly different. Comparing across studies, however, yields significantly different reaction times, despite being in the same direction and probably due to the same effect. More recent technology such as the use of Event-Related Potentials, or ERPs, has further researched the effect. ERPs in particular find that common ERP components such as the P290 and N400 are influenced by the negative words moreso than the neutral words. This implies that the effect is not due to semantic processing, as that would take much longer to complete and the effect would not be visible in time.

The evidence that the task yields different measurements when used on different populations, and without a firm explanation as to why, presents a significant problem. The results of the task should remain predictable based on the theory behind the measure despite using various methods and various populations, especially if it is to be considered a genuine measurement of interference effects.

Generalizability
It appears that the effects of the task depend on which format of the task used, how the information is presented, for example, blocked versus mixed format, and what population is tested. Many researchers use these tasks interchangeably, despite known differences. The generalizability of the task depends on which task is used and for which population.