Chi2-tests revealed that target evaluations across all subjects differ significantly from chance level for 33 out of 40 targets (p < .05 and p < .01). The evaluations paralleled the target’s categorization as “pleasant” or “unpleasant”. Hence, the participants mostly differentiated between good and bad words. Task involvement is thus considered to be sufficient.
The most prominent effect in the three-way analysis is the response latencies’
prolongation for unpleasant targets. The highly significant main effect for target valence (F (1,23) = 8.74, p < .01, η2 = .28) is congruent with study A. Nevertheless, a significant prime valence x target valence interaction (F (2,46) = 3.37, p < .05, η2 = .13) reveals that the prolongation in response latencies increases for unpleasant targets preceded by unpleasant primes. Figure 8.3 (next page) indicates significant post hoc results:
Affectively congruent unpleasant pairs produce response deceleration compared to affectively congruent pleasant pairs and affectively incongruent pairs. In short, the results are conform with the theoretically expected affective priming pattern.
Most importantly, no significant results were found for the treatment success. The insignificant main and interaction effect with the group factor indicated that treatment responders and non-responders did not differ in this experiment (p > .05). Figure 8.3 (next page) thus does not differentiate between both groups. No statistical significance was found for any other effect in the three-way analysis.
Figure 8.3 Prime x target valence: mean reaction times in ms and std. error7
Treatment effects: Different impact of NET and meditation on reaction times?
An additional analysis addressed the impact of the different PTSD treatments irrespective of PTSD-diagnosis: Narrative Exposure Therapy (M. Schauer et al., 2005) versus traditional meditation/chanting. Results did not reveal other effects than those described above: A significant main effect for target valence (p < .01) and a significant prime valence x target valence interaction (p < .05) that is comparable to the one illustrated in Figure 8.3.
Comparison of study A and B
As the Sri Lankan study aimed at replicating results of study A, both experiments have been compared statistically. All participants in Sri Lanka suffered at least once in their life from PTSD. In addition, both Sri Lankan groups (treatment responders and non-responders) did not differ statistically in reaction times and results did not change if considering the type of PTSD treatment. In conclusion, both groups were taken together in the comparison analysis.
7 Bars are depicted in hatched red, to illustrate the aggregation of both groups.
∗ ∗∗
∗
∗ p < .05
∗∗ p < .01
A highly significant main effect of target valence is most prominent again (F (1,47)
= 34.78, p < .00001): Prolonged response latencies for unpleasant targets are indicated.
However, a significant target valence x group interaction (F (2,47) = 3.38, p < .05) indicates that reaction times in both PTSD groups were more decelerated than in the Konstanz control group. Figure 8.4 indicates several highly significant post hoc tests: In both PTSD groups, response latencies for unpleasant targets were significantly longer than for pleasant targets in the same group and compared to the Konstanz control group (p < .01). Further effects within the comparison analysis were not of statistical interest.
Figure 8.4 Target valence x group: mean reaction times in ms and std. error
8.6 Discussion
Results among refugee adolescents in Germany/Austria (study A) revealed generally prolonged response latencies in an evaluative decision task for PTSD adolescents. Furthermore, a general response inhibition for unpleasant targets has been found for all participants. Separate group analyses support this general finding. But the response inhibition for unpleasant targets is particularly enhanced among PTSD adolescents. In addition, PTSD patients’ response latencies are also decelerated when the target was preceded by a pleasant or neutral prime.
∗∗
∗∗
∗∗
∗∗
∗ p < .05
∗∗ p < .01
The replication among treated PTSD adolescents in Sri Lanka (study B) resulted in a strong response inhibition for unpleasant targets, too. Affective priming was found in that the response inhibition for unpleasant targets is particularly enhanced when the target is preceded by an unpleasant prime. Reaction times for affectively incongruent prime target pairs were found to be in between of affectively congruent pairs. A significant effect has been found neither for treatment success nor for treatment type.
A final comparison between both experiments including the healthy control and the PTSD group of study A and a treated PTSD group (the complete sample of study B8) confirms this pattern of effects: The strong response inhibition for unpleasant
targets was found again as well as an enhanced response inhibition for unpleasant targets within both PTSD groups. Furthermore, a trend for an additional response inhibition for targets preceded by primes that are generally rated as neutral or positive was indicated in both PTSD groups. In summary, the response latency pattern of the treated PTSD patients in Sri Lanka was most similar to the PTSD group in study A, despite of some small differences.
The general findings are thus strengthened by replication, the absence of group differences (study A) in a general intelligence and a concentration test, and sufficient task involvement of all participants as evidenced by target evaluation above chance level and consistent evaluations compared to the prestudy ratings.
In the following paragraphs, results are evaluated with respect to expectations as specified in section 8.1. Paragraphs first refer to the general expectations and then to the PTSD-specific expectations. Furthermore, the respective literature and previous evidence will be considered as well as the limitations of both experiments. Finally, common conclusions will be dedicated.
General response inhibition for unpleasant words
In summary, the current experiment replicates previous evidence: Visually presented word pairs produce reliable response facilitation and inhibition (Bargh et al., 1992; Bargh et al., 1996; De Houwer et al., 1998; Fazio et al., 1986; K.C. Klauer &
Stern, 1992; Wentura, 1998, 2000).
8 As no group effects were found in study B (neither for PTSD diagnosis nor treatment type), groups were not differentiated for the final comparison.
Results mainly confirmed the a priori hypotheses about facilitation and inhibition effects. Affectively congruent pleasant prime target pairs triggered a response facilitation for the evaluative decision at least in study B. In contrast and found across both studies, the evaluative decision is inhibited for affectively congruent unpleasant pairs, referred to as reverse or negative priming. These findings are in line with the above cited literature (e.g., De Houwer et al., 2002; K.C. Klauer & Musch, 2003) that expect this complex response pattern particularly for evaluative decision tasks. The current experiment confirms once more the judgmental tendency model, as outlined in the introduction (De Houwer et al., 2002; K.C. Klauer & Musch, 2003; K.C. Klauer &
Stern, 1992; Wentura, 1998, 1999, 2000). According to this model, the affective congruence of prime and target causes a sense of plausibility. This feeling biases affirmative answers, as the answer “good word” is considered to be. Since this affirmative answer is only required by positively valenced target words, the bias for affirmative answers leads to response facilitation only for congruent pleasant pairs. For affectively congruent unpleasant pairs in contrast, the bias for affirmative answers inhibits the required answer “bad word” which is considered as dismissive. The response inhibition for unpleasant targets was particularly expressed in the current experiments. With respect to inhibition effects in control subjects, unpleasant stimuli have been chosen with respect to their valence as rated by ethnically comparable subjects. Thus, inhibited responses to unpleasant targets of control participants correspond with expectations.
Expectations for affectively incongruent prime target pairs were drawn out in line with the judgmental tendency model. It has been argued that affectively inconsistent pairs should lead to a feeling of implausibility and thus bias dismissive answers (K.C.
Klauer & Musch, 2003). As dismissive answers are only adequate for unpleasant targets, responses for pleasant – unpleasant pairs should be shorter than for unpleasant – pleasant. However, the expectation was not confirmed in both studies. Actually, both studies revealed that the response latencies for affectively incongruent prime target pairs were in between facilitated pleasant – pleasant and inhibited unpleasant – unpleasant answers. But the results did not allow further differentiation.
A priori hypotheses for incongruent prime target pairs that comprise neutral primes and an affective (pleasant or unpleasant) target are even more difficult on the basis of the literature. Complementing the same expectations as for affectively inconsistent pairs, inconsistency between a non-valenced and an either positively or
negatively valenced word might be less obvious or relevant for the recipient. It thus has less impact on judgmental tendencies. The reaction time should refer to the “pure time”
needed to evaluate a target word as good or bad (irrespective of a prime) and thus serves as kind of baseline condition. Unfortunately, this expectation was only found in study B (on a descriptive level). In study A, particularly the neutral-unpleasant condition produced longest response latencies. Since this prolongation of response latencies is mainly due to the PTSD group, this effect will be discussed in more detail in the next section.
Enhanced response inhibition for unpleasant words in PTSD samples
First of all, the dominant group effect should be discussed: PTSD patients took generally longer than controls to evaluate the target words. One might thus argue that the effects mainly reflect a general functional impairment in the clinical sample.
Obviously, this is true to some extent. Nevertheless, a generally reduced functionality does not explain all effects: Significant two-way interactions involving the group factor suggest that the PTSD patients’ responses are modulated by the experimental factors on a high level. These influences of prime and target valence on the response latencies in PTSD patients differ from those in the control group. A separate analysis of the PTSD group also resulted in a highly significant main effect for target valence: Reaction times were still prolonged for unpleasant targets. Thus, an enhanced response inhibition for unpleasant words has been found for PTSD adolescents in addition to the generally prolonged reaction times. The absence of group differences in general concentration ability and general intelligence further contradicts the argument that the generally prolonged response latencies are only due to the pathologically functional impairment.
How to interpret thus the PTSD patients’ enhanced response inhibition for unpleasant targets? Altered facilitation and inhibition effects were expected for the PTSD patients in study A and at least for the treatment non-responders in study B. The expectation is based on the assumption of extended associative fear structures in survivors of traumatic experiences that play an important role in the manifestation and chronification of PTSD symptoms (see section 3.1). The main argument for this expectation was formulated in that the pathologically extended fear structure comprises concepts of unpleasant valence. In addition to an enhanced number of included elements in such fear structure, particularly strengthened interconnections have been hypothesized for PTSD patients (Ehlers & Clark, 2000). Both pathological alterations
lead to a structure that can be easily triggered. Within the current experiment, this
“hyper-responsive” fear structure should prompt a strong interference between semantic activation of fear structure elements and the response tendencies. In line with the judgmental tendency model and the Stroop-like mechanism discussed for affective priming paradigms, a particularly enhanced inhibition effect for PTSD patients was expected. The enhanced response inhibition for unpleasant targets within the PTSD group particularly supports this argumentation. As the stimulus set for all participants was held the same and traumatic experiences varied across subjects in study A, unpleasant stimuli were not explicitly trauma-relevant in terms of their content. But the probability that the stimuli shared the (unpleasant) emotional arousal with trauma-relevant cues is high. This is in line with the fear structure model that comprises stimulus as well as response elements in all modalities. The emotional arousal is most probable to be stored in a traumatic associative fear structure.
Nevertheless, additional factors should be taken into account for the fact that PTSD patients in comparison to ethnically matched controls take more time to evaluate unpleasant targets as such in the current study A. The effect might reflect pathological avoidance behavior for fear provoking material. As already described in DSM-IV (APA, 2000), active and passive avoidance (see section 2) is a prominent part of the clinical PTSD manifestation. The typical PTSD symptoms would suggest the avoidance of responses to emotion (fear) provoking stimuli. Schauer et al. (2005) describe that many PTSD patients have learned to avoid cues that remind them of the originally frightening event since even recollection of the memory is experienced as very painful and frightening. The fact that words whose content is not trauma-relevant trigger the
“avoidance behavior”, argues for the extended associative fear structure. It provides another argument to underline the assumptions of unpleasant valence to be separately contained in the structure.
What about enhanced response inhibition even for trials with pleasant and neutral primes? Evaluative decision is expected to be inhibited for subjectively congruent prime target pairs of unpleasant valence (K.C. Klauer & Musch, 2003). Previous investigations already evidenced that pathologically altered evaluations of presented stimuli are reflected in altered priming effects. For instance, such results have been reported for manifest patients and subjects at a high risk for schizophrenia (Lecardeur et al., 2007; van't Wout et al., 2004) or anxiety disorders (Dannlowski, Kersting, Arolt et al., 2006; Schneider & Schulte, 2007; Schniering & Rapee, 1997). A single study
presenting disorder-related verbal stimuli to PTSD patients was unfortunately not comparable to the current one for several reasons. However, disorder-related priming effects in a word stem completion task were reported for PTSD patients (Michael et al., 2005). Disorder-related priming was indicated as more word stem completions for trauma-related words. Further investigations among PTSD populations (Amir et al., 1996; McNally & Amir, 1996) suggest additionally altered stimulus processing such as lower subjective noise evaluations when primed with trauma-related sentences. But these studies have even less in common with the current experiment and results are somewhat inconsistent.
Moors, De Houwer, Hermans, and Eelen (2005) as well as Fazio (2001) emphasize the impact of subjective appraisal processes for experimentally applied primes. In conclusion, the a priori pleasant and neutral primes might have a subjective relation to unpleasant valence for PTSD patients. Indeed, results of study A are in line with this argumentation as PTSD patients tended to show stronger response inhibition even for primes that have been previously rated as pleasant or neutral. Considering the model of judgmental tendencies, the results suggest that the subjective meaning of these primes is more similar to those of unpleasant words in PTSD patients. This could be interpreted as indicator for the extended fear structure that comprises both prime and target stimuli.
The pathologically enlarged memory representations are assumed to be easily triggered by such stimuli changed in their subjective meaning. The results thus give an empirical support to explain frequent clinical intrusion symptoms by the extended traumatic associative (fear) structure. The current dissertation calls into question the PTSD patients’ frequent description of intrusion symptoms to come “out of the blue”. It is rather hypothesized that numerous environmental cues trigger the activation of the associative fear structure and cause the re-experiencing symptoms. This fear structure triggering will not necessarily be consciously accessible to the patient. The current results suggest this conclusion in that the conscious evaluation of the target did not differ between patients and controls, but reaction times were modulated in different ways. In line with the cortical plasticity hypothesis, those elements can be included into the structure that are not primarily related to the traumatic experience. Elbert and colleagues (2006) describe that the representational structure may be successively enlarged with every recall by including even elements of the recall environment. Thus,
the probability to encounter a stimulus once related to an original traumatic experience or a pathological recall situation is high in every day life. In addition, the “encounter probability” increases with every recall.
The results suggest a) the activation of the fear structure by not necessarily trauma-relevant stimuli and b) altered relationships in PTSD patients between
“normally” pleasant and neutral material.
Field study replication
Replication of the discussed PTSD-specific results is particularly important because of the novelty of the findings. Generally speaking, study B replicated results of study A with respect to insights in altered processing of affective stimuli in PTSD patients. A comparison analysis between study A and B statistically confirmed the similarities between the PTSD group in study A and the treated PTSD group in study B.
More specifically, response inhibition was again found for unpleasant targets. Affective priming was indicated in that the response inhibition was enhanced for congruent unpleasant prime target pairs.
Furthermore, the replication study supports the argumentation of Neuner et al.
(2003) as well as Schauer et al. (2005) in that no differences were found for treatment success. Treatment responders and non-responders suffered at least once in their life from PTSD. In the literature, it is unclear if treatment modifies associative fear structures. Neuner et al. (2003) and Schauer et al. (2005) doubt the assumption that the associative fear structure of a traumatic experience is changed by a therapeutic process.
Instead, its controllability is assumed to be modified by therapy. This view is further encouraged in that no differences in relation to the provided treatment (Narrative exposure therapy versus meditation/relaxation) were found. Narrative Exposure Therapy aims at constructing a consistent autobiographical representation of the experienced traumatic event and therefore allows habituation processes and reduction of fear responses over the time (M. Schauer et al., 2005). Meditation/relaxation therapy in contrast does not deal with traumatic memory representations but rather addresses general stress management strategies by breathing, relaxation, and meditation techniques as well as traditional chanting. The failed group differentiation according to treatment success and type of treatment suggests that both treatment success as well as treatment focus do not influence the PTSD-specific fear structure as assessed in the current experiment.
The replication trial argues for the current experimental design that comparable findings were obtained in both trials for refugees in western countries and survivors of traumatic experiences in their country of origin. On the other hand, these different experimental conditions set some limits to drawing conclusions. Besides the refugee versus country of origin perspective that leads also to a second language (study A) – native speaker (study B) contrast, study A and B differed in some additional points.
First of all, group assignments were not the same as study B was realized within a larger treatment study. Furthermore, the set of stimuli was not completely paralleled, and experimental conditions varied: Whereas in study A an individual testing was possible, subjects in study B were more likely to be distracted by e.g. other children running around. More differences could be identified in that for instance computer use and the white experimenter was less usual for Sri Lankan participants. It could be further speculated if groups in study A and B further varied in their habituation to a life-threatening environment. While refugees in Germany lived in a safe environment, the Sri Lanka study was conducted a few months after the tsunami and in a tense political situation: Another escalation of the Sri Lankan civil war was feared. Anyhow, the general replication success suggests an intercultural applicability of the design.
Findings in both studies are strengthened in that all participants were properly involved in the evaluative decision task. This is evidenced in that evaluative decisions for each target were consistent across subjects and in that the evaluation paralleled the prestudy and students’ ratings (Herbert et al., 2006).
Limitations
The current studies are once more limited by the small and heterogeneous group sizes that unfortunately do not provide enough power to correct post hoc tests with Bonferroni adjustment, for instance. Hence, future studies should aim at replicating the
The current studies are once more limited by the small and heterogeneous group sizes that unfortunately do not provide enough power to correct post hoc tests with Bonferroni adjustment, for instance. Hence, future studies should aim at replicating the