The Stroop effect (Ridley 1935 cited by MacLeod and MacDonald 2000) examines how automatic processing can be facilitated or hindered based on which cognitive processes are more automated than others. The classic Stroop requires that participant identify the colour a word appears in, rather than attending to the reading of the word, itself. Participants do not generally experience difficulty identifying the colour a word is printed in unless the word happens to be incongruent with the colour; the word green written in red ink will result in slowing of processing and more errors, but the word red written in red ink facilities performance and a neutral word, such as the word cat written in green ink will not hinder the identification of the colour (MacLeod and MacDonald 2000). The reason for this is believed to be automaticity inferring with what is attended to. The human brain is more inclined to read the word than to
Page | 5-138 attempt to identify the colour it is printed in as humans rely on reading more than colour identification, making that task more automatic. It is believed that the Stroop captures attention as well as automaticity in performance, though it is important to note that the mechanisms behind the Stroop are not currently understood (Power 2006).
Similarly, the emotional Stroop is a task that requires that individuals name the colour, rather than attend to the word, itself. However, in this case the word is emotionally valenced, and the interference is caused by the participant attending to the emotional valence of the word, rather than the colour it appears in. It is important to note that the term emotional Stroop is a misnomer. The phenomenon experienced is not identical to that experienced in the classic Stroop (Frings et al. 2009). There is not an incongruence between word colour and word meaning that occurs, rather the interference that occurs is a consequence of attention or over attention to the word’s meaning. Despite this misnomer the emotional Stroop is considered a good measure of attendance or over attendance to emotionally valenced stimuli, depending on the research paradigm and sample involved of emotional attention (Price 2011).
There are several studies that demonstrate the emotional Stroop effect which suggest that individuals will attend to the meaning and emotion of a word, rather than the colour, resulting in increased response latencies as well as increases in errors (see Table). This work has been expanded to examine the relationships between specific emotions and their links with disorders and mental illnesses, as well as emotion and anti-social behaviour and criminal behaviours. The salience of an emotionally valenced word seems to result in response latencies; the more relevant the word to the participant, the greater attentional bias, resulting in response latencies and increased errors in performance. The salience of a particular word to an individual results in
Page | 5-139 biases. This is evident in both clinical and non-clinical samples, whereby a word that is particularly relevant to an individual will result in response latencies.
There has been substantial research that utilises the emotional Stroop to examine emotion and attention with those who experience exaggerated emotional responses due to underlying mental illness or disorder. A review conducted by Chen (2008) discusses the how the emotional Stroop has been used to explore attentional biases among those with social phobias, anxiety disorder, alcoholism, and compulsive behaviours. Research often demonstrated, depending on the effectiveness of the design, that individuals with certain types of mental illness or disorder demonstrate a bias for words that are particularly salient to them over other stimuli with greater errors and response latencies. Smith and Waterman (2004) found that sex offenders demonstrated a bias towards words that were sexual in nature including differences based on type of offense, i.e. rapists and paedophiles responded with differential biases based on the salience of the sexually evocative words employed in the emotional Stroop paradigm. Similarly they found that violent sexual offenders compared with non-violent sexual offenders showed similar biases for violent words when compared. Smith and Waterman (2003) also found that when compared with university students, violent offenders were more prone to response bias for aggressive words than their research counterparts. Price (2011) replicated the work of Smith and Waterman using the emotional Stroop design combined with functional neuroimaging techniques to capture the neurocognitive differences between sex offenders and their healthy research counter parts. Like Smith and Waterman (2004), Price’s (2011) study provided evidence of biases in sex-offenders, for example youth sex offenders toward sexually salient word lists, while the results were not terribly significant they provided evidence for use of the emotional Stroop with offender samples.
Page | 5-140 There are thought to be two mechanisms beyond the emotional Stroop. The fast and slow effects (Chajut et al.2010). The fast effect is the trial dependent effect which is the reaction the individual has to the word as it is appears on the screen and is affected by an increase in arousal precipitated by the emotional stimuli (Chajut et al. 2010). The slow effect is the effect a particular word may have across trials and is theorised to be a consequence of an inability to disengage from the emotional valence of the stimuli (Chajut et al. 2010). The slow effect is of particular interest in the emotional Stroop task as it is said to demonstrate that the emotional valence of a particular word causes a general slowing down of response across a number of subsequent trials as a consequence of the participants’ neurocognitive resources being allocated to the meaning of a particular word. While the cause of the slowing down is not entirely understood, the slow effect has been captured in studies of healthy participants, as well as those with mental illness disorder addiction and trauma (See Table 1). Chajut et al. (2010) argue that the reason for the emotional Stroop effect is that, under laboratory conditions, individuals are forced to ‘confront’ threat based stimuli rather than avoid or retreat from a threat based stimuli and that if provided a means of retreat the emotional Stroop effect may not occur.