Reasoning, trauma, and PTSD: insights into emotion–cognition interaction
REASONING, TRAUMA, AND PTSD
Insights into emotion-cognition interactions
Isabelle Blanchette and Sara-Valerie Giroux
Certain experiences in life are extremely distinctive. Situations where an individual’s safety or integrity is compromised can generate extreme levels of emotion: fear, horror, and anguish. These experiences mark significant moments in life and lay down long-lasting and vivid memory traces. What is their impact on other cognitive processes such as reasoning? Emotions are typically thought of as antithetic to rational thought, but research in the past 40 years has provided a much richer portrait of the complex interactions between emotion and cognition. In this chapter, we examine how the experience of highly emotional events is associated with higher level cognitive function, and what this may tell us about the interaction between emotion and cognition.
We focus on reasoning as one example of a higher level cognitive process. Higher level cognitive function requires complex operations, often voluntary control and awareness. Reasoning is the process through which inferences are drawn. The ability to reason analytically is commonly held as one of the hallmarks of the rational mind. In this chapter, we ask how reasoning is affected by trauma, but also how analytic thinking can shape the experience of trauma.
Before diving into the cognitive aspects, we explore how prevalent the experience of trauma is. To determine implications for the normal mind, we need to know what normal is. While traumatic events are exceptional, in the sense that they occur rarely and that they generate incomparable levels of emotion, they are nevertheless normal, in the sense that they are experienced by a majority of the population. Following this global portrait of trauma, we examine how trauma exposure and post-traumatic stress disorder (PTSD) negatively impact analytic reasoning. We then explore how trauma affects precursor mechanisms, specifically working memory and attention, and how this may have cascade effects on reasoning. We review studies showing that higher level cognitive abilities, indexed by IQ or developed through education, can influence the experience of trauma. We draw on all this research to present novel insights into the emotion-cognition interactions and integrate these in a preliminary theoretical model.
2 Prevalence of trauma exposure
About 69-89% of individuals will experience a traumatic event at one point in their life (Breslau, 2009; Resnick et al., 1993; Van Ameringen et al., 2008). A traumatic event is defined in the DSM-V (American Psychiatric Association, 2013) as an event that involves actual or threatened death or serious injury, or a threat to the physical integrity of self or others. Such events evoke feelings of intense fear, helplessness, or horror. Hence, a traumatic event is defined by the person’s emotional reaction, not solely by the characteristics of the event itself. Trauma, therefore, necessarily involves the interaction between emotion and cognition as it rests on the person’s representation of the event as being life-threatening and the associated emotional reactions. Strictly speaking, certain events such as car accidents, physical assaults, or natural disasters are ‘potentially traumatic’; whether they are traumatic varies across individuals. For short, we will use the term ‘trauma exposure’ to refer to exposure to a potentially traumatic event.
Epidemiological studies assessing the prevalence of trauma typically present a list of potentially traumatic events. Participants must indicate whether they have experienced each event. There is usually an ‘all other traumas’ category, where participants can report any other event that has evoked these feelings of fear, helplessness, or horror, or when they have felt that their safety or integrity was threatened.
In high-income countries (where the majority of studies have been conducted), the most common traumas reported are the unexpected death of a loved one, sexual assault, and seeing someone badly injured or killed (see Breslau, 2009; Van Ameringen et al., 2008). Exposure to at least one potentially traumatic event is very high even in relatively young individuals; for instance, up to 85% of college students report experiencing at least one potentially traumatic event (Frazier et al., 2009).
Recent worldwide surveys confirm similar levels of exposure globally. The World Health Organisation Mental Health Survey combines epidemiological surveys with nationally representative samples from 26 countries, ranging from lower income countries such as Nigeria and the Ukraine to higher income countries such Italy and New-Zealand (Kessler et al., 2017). More than 70,000 respondents were asked about 29 types of events, including war, accidents, and interpersonal violence. Global exposure rate was 70.4%. The most frequently reported traumas were the unexpected death of a loved one and witnessing death or serious injury.
In specific areas of the globe, where political and economic instability are high, or where there is war or armed conflicts, exposure to trauma can be even more prevalent and more severe. We have worked with participants in Rwanda and the Democratic Republic of Congo (DRC). During the 1994 genocide against the Tutsis in Rwanda, and over the period of chronic armed conflicts in the North-East of the DRC since 1994, individuals have been exposed to a range of traumatic events. In one of our studies in Rwanda, more than 90% of participants (from an m > 700) experienced the death of a loved one during the genocide, more than 80% had to flee their home, and more than 10% reported being raped. In the DRC, over 70% of the 220 participants in one of our studies directly witnessed armed combat. Over half were physically assaulted, threatened with a machete, or tortured. Kidnapping of a loved one was reported by half of participants. One out of two women experienced rape or sexual assault. Again, trauma exposure is not restricted to adults. One study conducted in Butembo, in the DRC, found that close to 75% of children had lost a family member and over 95% had experienced shooting (Masinda and Muhesi, 2004). These data illustrate the cumulation of potentially traumatic events faced by individuals living in parts of the globe afflicted by armed conflicts.
While trauma exposure is prevalent, only a minority of individuals will develop a post-traumatic stress disorder following such events. PTSD is a psychological disorder characterized by the persistent re-experiencing of a traumatic event, as well as alterations in mood, cognition, arousal, and reactivity (American Psychiatric Association, 2013). Intrusions are a cardinal feature of PTSD. These are unsolicited memories of negative past events, often in the form of images or sensory impressions, that are experienced as if occurring in the present. Breslau (2009) estimates that 6.8% of participants exposed to trauma will develop PTSD, based on the combined prevalence across nine studies. In the World Health Organisation (WHO) surveys conducted with representative community samples, lifetime prevalence of PTSD was estimated at 3.9% in the total sample, and 5.6% among trauma-exposed participants (Koenen et al., 2017). Certain types of traumas, notably sexual violence, intimate partner violence, and physical assault are more likely to lead to the development of PTSD, compared to others such as natural disasters (Breslau, 2009; Kessler et al., 2017). The cumulation of trauma also increases the likelihood of developing PTSD. Nevertheless, while a large majority of the population will be exposed to at least one form of trauma during their lifetime, only a minority of participants will suffer from PTSD.
The rates of PTSD may however be much higher in geographic areas such as Rwanda or the DRC where people experience a multitude of potentially traumatic events. In Rwanda, one study with a nationally representative sample estimated the prevalence of PTSD to be 26%, 14 years after the end of the 1994 genocide (Mun-yandamutsa et al., 2012). In our own sample of over 700 participants (not intended to be representative), tested between 2014 and 2018, the estimated rate of PTSD was 21%. The rate is higher when focusing on genocide survivors. In 2018 and 2019, 181 mothers who were genocide survivors participated in one of our studies; 61 of them (34%) met the criterion for probable PTSD. In North Kivu (DRC), we conducted a study in a period of ongoing armed conflicts; one out of three participants met the criteria for probable PTSD.
The rates observed in our studies generally concur with a recent meta-analysis of 33 studies of mental health in civilians exposed to war that estimated PTSD rates of 26% (Morina et al., 2018). A different recent study quantified the global prevalence of war exposure and PTSD by combining geolocated data on armed conflicts
(from the Uppsala Conflict Data Program) and epidemiological surveys of mental health (Hoppen and Morina, 2019). Between 1989 and 2015, 1.45 billion people were exposed to war, of which 452 million likely suffered from PTSD. Most war survivors live in low-income countries like Uganda, Liberia, Sudan, and Palestine.
Altogether trauma exposure is highly prevalent, across the globe. In high-income and relatively safe countries, only a minority of participants exposed to trauma will suffer from PTSD. In areas exposed to armed conflicts, individuals are more likely to be exposed to a cumulation of events that threaten their safety and integrity. In such circumstances, rates of PTSD in the population are much higher, and may remain high for very long periods. Traumatic events are associated with intense feelings of fear, helplessness, or horror. They are exceptional in the sense that they evoke a level of emotional intensity that is rarely experienced in a lifetime. Investigating how these experiences, with or without PTSD, may be related to cognitive function offers a window into the interaction between emotion and cognition.
3 Reasoning and other cognitive correlates of trauma
In this section, we examine how trauma is related to reasoning. We will use the term trauma to refer to trauma exposure and PTSD indistinctly and use the specific terms when an effect is uniquely related to either PTSD or trauma exposure. We will present how trauma is negatively related to analytic reasoning. To explain this deleterious effect, we will draw upon the effect of trauma on two antecedent processes: working memory (WM) and attention. This will lead us to the hypothesis that attentional prioritizing of trauma-related information may start a cascade of cognitive operations resulting in reduced availability of cognitive resources, which negatively impacts analytic reasoning.
Reasoning and higher level cognitive processes
Reasoning is a complex process that can be accomplished through explicit, systematic processing of the structural features of arguments, for instance, through logic or statistical reasoning (Ball and Thompson, 2018). This type of process can be labelled analytic thinking. It can be contrasted with heuristic processing, which subsumes the reasoning processes that are less systematic, more likely to be based on intuition, influenced by semantic content, beliefs, and context. Analytic reasoning exemplifies the human capacity for abstract thinking. It can be influenced by a number of things, including emotion (Blanchette and Richards, 2004, 2010).
Trauma-related contents can decrease analytic thinking. In one study (Eliades et al., 2012), women survivors of sexual violence and controls reasoned about logical problems with neutral, emotional, or sexual abuse-related contents. Responses could be based on logic or belief. When participants reasoned about sexual abuse contents, they were more likely to display heuristic thinking and less likely to display analytic thinking. This was the case for both victims and non-victims. The sexual abuse-related contents were judged to be highly emotional, and personally relevant, by both groups of women, whether they reported personal experiences of sexual violence or not (we come back to the role of personal relevance later in the chapter).
We observed analogous results in a study examining statistical reasoning emotion (Eliades et al., 2013). We used the base rate task which indexes the extent to which participants rely on statistical vs. anecdotal information in drawing inferences. We compared problems with neutral contents to problems related to sexual abuse, using stimuli such as: In a sample of 1000 persons, 5 are rapists. Mike is 30 years old. He enjoys watching child pornography, has few friends, and is generally a mysterious person. . . . Participants were more likely to rely on heuristic processing, in this case anecdotal information, as opposed to statistical information when the contents were trauma related. In this study, the difference between trauma and neutral problems was greater for survivors of sexual violence than controls; they also judged these contents to be more emotional.
These two studies illustrate how reasoning about trauma-related contents can be associated with decrements in analytic thinking. Other studies have documented generic deficits in analytic thinking as a function of PTSD. For instance, in a group of UK veterans, logical reasoning was reduced for participants suffering from PTSD, compared to non-PTSD veterans (Blanchette et al., 2014). In our studies in Rwanda, trauma exposure and PTSD symptoms are negatively correlated with analytic reasoning (Caparos et al., 2018). In addition to the reasoning tasks, we also measured symbolic thinking using the matrices subtest of the Weschler Adult Intelligence Subscale, and this was also negatively related to both trauma exposure and PTSD symptoms.
PTSD may also be associated with more encompassing deficits in higher order cognitive function, notably in so-called executive functions (Polak et al., 2012; Scott et al., 2015). While this is a very broad category, some studies of executive function have included tasks measuring analytic or symbolic thinking, often taken from intelligence tests (Scott et al., 2015). Most findings confirm a negative correlation between PTSD and performance on these tests of analytic thinking.
Altogether studies suggest that trauma-related contents and the experience of trauma or PTSD are associated with decreased analytic reasoning or symbolic thinking. Analytic reasoning has been measured using syllogisms, conditional reasoning, or base rate tasks, taken from the psychology of reasoning literature. Symbolic or abstract thinking has often been measured using neuropsychological tests, for instance, subscales from IQ tests. The two cognitive abilities are highly related, though not entirely overlapping (Stanovich, 2009). Both, however, rely heavily on WM, which is also related to trauma. In the next section, we examine the link between trauma and WM as a potential precursor of its effect on reasoning.
The experience of trauma is associated with working memory deficits. In one study with patients suffering from psychiatric disorders, a history of trauma was associated with lower performance on three different working memory tasks (alphabetic span, OSpan, and running span; El-Hage et al., 2006). In non-psychiatric samples, the number of stressful life events reported negatively correlates with working memory performance, measured with the OSpan task (Klein and Boals, 2001). Similarly, in four studies, we found that women who experienced sexual abuse, on average, showed lower WM performance (measured using the Reading Span task) than non-victims matched for age and education (Blanchette and Caparos, 2016). Women who suffered experiences of sexual abuse also reported a greater number of stressful life events generally; the number of life events reported was negatively correlated with WM performance. A failure to replicate the link between stressful life events and WM performance has recently been reported (Goller et al., 2020), so the link be restricted to potentially traumatic events, and not negative, or stressful life events generally.
Our studies in Rwanda further document the link between trauma exposure, PTSD, and WM (Blanchette et al., 2019). Participants completed a measure of verbal storage (a forward digit span task). They also answered questions about the severity of their experiences during the 1994 genocide. Participants who reported a greater number of potentially traumatic experiences showed poorer performance on the digit span task. This was more than 20 years after the events occurred. We more recently observed the same negative correlation between trauma exposure and performance on the digit span (both forwards and backwards) in the DRC, during a time of ongoing violence (Kankunda, Balumé, Caparos and Blanchette, in preparation).
The relationship between trauma and WM has also been observed in children, in this case using both visual and verbal WM tasks. Children exposed to family violence (DePrince et al., 2009) or chronic stress (Masson et al., 2016) show poorer WM performance, even when controlling for anxiety, socioeconomic status, and potential brain trauma. Effects of early childhood adversity on WM can persist into adulthood (see Goodman et al., 2019, for a meta-analysis).
In addition to trauma exposure, psychopathological symptoms are also related to WM function. Patients suffering from PTSD show poorer WM performance compared to healthy controls exposed to the same events. For instance, Iraqi, American and Bosnian veterans suffering from PTSD presented lower WM performance than healthy veterans exposed to similar combat experiences (Honzel et al., 2014; Koso & Hansen, 2006). Different meta-analyses and narrative reviews confirm that participants suffering from PTSD generally show poorer WM performance than age- and education-matched controls (Aupperle et al., 2012; Buckley et al., 2000; Polak et al., 2012; Scott et al., 2015).
One hypothesis suggests that thoughts related to negative events compete for working memory resources (Klein and Boals, 2001). One feature of emotional memories, particularly of highly emotional events, is that they are more likely to be activated, spontaneously or as a result of retrieval cues, in memory networks. The activation of trauma-related thoughts may capture WM resources, leaving less resources available to process task-related stimuli, especially in cognitively demanding tasks. This hypothesis has yet to be tested directly.
One important methodological issue needs to be considered: in most studies of trauma and WM, participants answer questions about their difficult past experiences and their psychological symptoms in the same session as they complete the cognitive assessments. Trauma-related thoughts have thus typically been primed through answering the questionnaires. This may increase the strength of the link between WM and trauma. The correlation between trauma and WM may be weaker when trauma-related thoughts have not been primed. Studies examining the impact of task order (WM first vs. questionnaires first) or using separate sessions to assess trauma experiences and cognitive function are required to explore this further.
Nevertheless, the negative link between trauma and WM appears to be robust. It is also consistent with the effects observed for analytic reasoning and symbolic thinking, which heavily rely on WM (Süß et al., 2002). Ifintrusive thoughts related to trauma weigh on WM, especially in individuals suffering from PSTD, this would decrease the likelihood of conjuring analytic processes when reasoning.
Most WM and trauma studies have examined performance with neutral (or trauma-unrelated) contents. Some studies have compared WM for emotional and neutral information. One recent meta-analysis suggests that in healthy populations, the affective nature of the information does not have an important impact on WM processing, but that it does in patients suffering from mental health problems (Schweizer et al., 2019). This meta-analysis did not break down results by type of psychopathology' but it did include studies with patients suffering from PTSD. In patients, WM accuracy was negatively impacted by the presence of emotional contents. This points to a possible link between attention, WM, and trauma, this is what we explore next.
At least two dimensions of attention are impacted by trauma: attentional control and attentional bias. Attentional control refers to the ability to focus on relevant stimuli and ignore irrelevant stimuli. It is closely related to WM capacity (Oberauer, 2019). Attentional bias describes the extent to which the processing of specific types of contents, for example, trauma-related information, is prioritized over other information.
Attentional control can be examined using tasks such as the go-no-go, the Stroop task, and the Attentional Network Task. Meta-analyses confirm that attentional control is generally impaired in individuals suffering from PTSD, relative to nonexposed controls, and compared to exposed participants who do not suffer from PTSD (Aupperle et al., 2012; Polak et al., 2012). One meta-analysis estimates that the difference in executive function, including attentional control, is of moderate amplitude, between d = -.45 and -0.5. Thus, individuals suffering from PTSD have more difficulty focusing on task goals and/or inhibiting the processing of distracters.
An attentional bias towards trauma-related contents has been documented in many studies. One popular paradigm is the emotional Stroop task, where words are presented in different colours that participants must identify. Longer reaction times to name the colour of trauma-related contents is taken as an indication of increased attentional allocation to these semantic contents. The experience of trauma is closely related to this interference. For instance, in one study, sexual abuse victims and non-exposed controls named the colour of trauma-related, generally emotional and neutral words (Caparos and Blanchette, 2014). Trauma-related contents led to longer reactions times, compared to the emotional and neutral contents. The level of interference from trauma-related contents was linearly related to the severity of the abuse reported (r = 0.27) and to participants’ subjective emotional evaluation of the contents. This type of attentional bias has been confirmed in a number of reviews of the literature on sexual abuse (Latack et al., 2017) as well as other types of traumas (Buckley et al., 2000; McNally, 2006).1
Trauma-related stimuli are thus prioritized. Further, it may be more difficult for individuals suffering from PTSD to inhibit distracters, including task-irrelevant thoughts related to trauma, to effectively allocate attentional resources towards task-relevant stimuli. This has implications for analytic thinking, which relies heavily on working memory and effective attentional control.
Personally relevant semantic contents
The evidence reviewed so far establishes that PTSD and trauma exposure have a deleterious impact on reasoning, and this impact is coherent with the effect of trauma on working memory and attention. Most studies of trauma and reasoning have evaluated cognitive function using generic, neutral contents. Analytic reasoning is impaired when reasoning about neutral contents; similarly, working memory is depleted when evaluated with digits, letters, or abstract shapes.
Research shows that semantic content can have a formidable impact on reasoning and other higher level cognitive processes. Thus, it may be important to consider what happens when trauma victims are processing information semantically related to trauma, which is personally relevant.
Personal relevance can indeed modulate the impact of emotion on analytical reasoning. For instance, we studied reasoning following coordinated terrorist attacks that occurred in London in 2004 (Blanchette et al., 2007). In one of these attacks, a bomb exploded on a bus. This occurred close to a university where we were able to interview people in the following week. We presented reasoning problems with neutral, emotional, or terrorism-related contents. We expected that participants would report higher levels of emotion and be more likely to reason based on beliefs (and stereotypes) when they were closer to the events. We used syllogisms such as the following: Some Muslims are terrorists; Some terrorists are suicide bombers; Therefore, some suicide bombings are doue by Muslims, where logical and belief-based answers conflict. We compared the answers of participants in London to those of participants in Manchester, in the North of England, London, Ontario, and Canada. As predicted, participants in London reported higher levels of emotion. Contrary to expectation, they provided more logical answers to conflict problems related to terrorism.
Participants were thus more likely to reason analytically, and less likely to reason heuristically, when reasoning about emotional personally relevant topics.
We observed similar mitigation of the effect of emotion by personal relevance in another study with victims of severe car accidents or sexual abuse (Caparos and Blanchette, 2017). Participants reasoned about neutral contents, car accidents, or sexual abuse. Personal relevance systematically mitigated the effect of emotion on reasoning: victims of car accidents made more errors of logic on the sexual abuse than the neutral problems, but not on the car accident problems. Inversely, sexual abuse victims made more errors of logic on accident-related contents, but not sexual-abuse related contents, compared to neutral problems. Thus, emotional contents decreased analytic reasoning, except when these contents were personally relevant.
Studies exploring the role of personal relevance in emotional reasoning are still scarce. One other program of research confirms similar emotion-enhancing effects of emotion in psychopathology' (Gangemi et al., 2014; Johnson-Laird et al., 2006). Participants suffering from varied psychopathologies, including depression and obsessive-compulsive disorder, displayed more logical reasoning when reasoning about contents related to their condition.
Nevertheless, emotion-enhancing effects on reasoning can be small and inconsistent. For example, in the study of belief bias and base rate neglect reported at the beginning of this chapter, sexual abuse victims did not exhibit more analytic reasoning than non-exposed women even though problems concerned sexual abuse. This may be because of the unfortunately high prevalence of sexual abuse; all women may process these contents as personally relevant. More research is needed to confirm that personal relevance mitigates the impact of trauma on reasoning.
There are however parallel findings concerning episodic memory illustrating that relevance can moderate the impact of trauma on cognitive function. The experience of trauma negatively impacts generic episodic memory. Individuals who have experienced trauma and/or suffer from PTSD show deficits in verbal episodic memory compared to non-exposed controls (Brewin et al., 2007). For example, victims of sexual abuse show poorer free recall and recognition of neutral and generally emotional short stories narrated to them, compared to non-exposed controls matched for age and education (Grégoire et al., 2020). There is a negative association between PTSD and verbal episodic memory, estimated to be of small to moderate size (Brewin et al., 2007; Buckley et al., 2000).
Trauma-related contents however mitigate these observed deficits in episodic memory (Grégoire et al., 2020). In our studies, victims did not differ from controls in their memory for short stories related to sexual abuse (a date rape scenario). Analogous findings were observed in a study' of Holocaust survivors who showed no deficit in remembering paired-associates when the contents were related to the Holocaust (Golier et al., 2003).
Results from studies of episodic memory are consistent with those observed in reasoning studies. Both could be explained by the attentional prioritizing of personally' relevant, trauma-related contents. This would counteract the depletion of attentional or working memory resources. The increased motivation to accurately process and represent these contents in working memory may also play a role (Blanchette and Caparos, 2013).
Altogether these studies highlight the important point that trauma does not necessarily have a universally negative impact on cognitive function. Trauma does not necessarily impair episodic memory or analytic reasoning. Before exploring the mechanisms responsible for the impact of trauma on cognition further, we examine the reverse relation: the impact of higher level cognition on the experience of trauma.
4 Impact of cognitive function on trauma
Experiencing highly emotional events can influence cognitive function, for participants who develop PTSD as well as those who do not. There is also evidence for the reverse relation: that higher level cognitive function can impact the experience of trauma. In this section, we present studies showing that IQ and education protect against the development of PTSD. We also describe the role granted to symbolic processing in PTSD models. These two lines of research suggest that symbolic thinking may be intrinsically related to the encoding (and subsequent regulation) of emotional experiences.
Intelligence, education, and PTSD
IQ is correlated with PTSD symptoms. Across studies of adults and children, individuals with lower IQ on average experience more severe PTSD symptoms (Buckley et al., 2000; Malarbi et al., 2017).
The relationship between IQ and PTSD may run in both directions. Trauma and PTSD could reduce global cognitive functioning; however, increased cognitive ability may also protect against the development of PTSD symptoms. Most studies are correlational and do not make it possible to differentiate between these two options. But there are a few studies using prospective and other designs showing that IQ represents a pre-existing vulnerability for the development of PTSD.
In one such study, Gilbertson and colleagues (Gilbertson et al., 2006) tested the IQ of 49 Vietnam veterans and that of their identical twin brothers. About half of the veterans had developed PTSD following combat exposure. These veterans suffering from PTSD had lower IQs than the non-PTSD veterans (the average difference was of 14 IQ points). However, the same difference existed for the brothers who had not been exposed to combat. This strongly suggests that the lower IQ of the veterans who developed PTSD existed prior to combat exposure rather than result from PTSD.
Similar conclusions were reached in a prospective study of 4000 young adults in Australia (Parslow andjorm, 2007). The sample had been constituted to examine the factors that affect cognitive functioning over the years. Participants were tested for a wide range of cognitive functions, including verbal intelligence, episodic memory, and working memory. Three years after the initial test, a severe bushfire occurred in the area, resulting in over 5000 evacuations, 400 injuries, and 5 deaths.
Of the original participants, 1500 experienced a form of trauma related to this event. They were tested again, 36 weeks after the events, and their PTSD symptoms were evaluated. Participants with lower performance on all initial neurocognitive measures showed higher levels of PTSD symptoms. This evidence also supports the conclusion that lower IQ represents a risk factor for the development of PTSD.
Education also seems to protect against the development of PTSD symptoms. One study examined the PTSD symptom trajectory of over 10,000 responders (police officers and others) involved in rescue, recovery, and clean-up after the attacks on the World Trade Centre in 2001 (Pietrzak et al., 2014). Higher education attainment protected against the more negative trajectories (severe chronic, delayed onset, etc.). Another prospective study confirms this in the Israel military (Kaplan et al., 2002). Intellectual functioning and educational attainment were measured before exposure to operations, as part of the screening process. Participants who later suffered from PTSD (« = 901) had lower IQ and educational attainment compared to their age-matched healthy controls, who were adolescents attending the same high schools. In another study in Armenia, researchers interviewed the survivors of a major earthquake (that caused 25,000 deaths) 23 years after the event (Goenjian et al., 2018). Those with higher levels of education were less likely to suffer from chronic PTSD.
Education and IQ are highly correlated. In high-income countries, where general levels of educational attainment are quite high, IQ (or general cognitive ability) is an important determinant of educational success (Strenze, 2007). Most studies on trauma, IQ, and education have been conducted in high-income. In lower-income countries, the number of years in formal schooling is more variable across the population and depends on a wide range of factors unrelated to cognitive ability. Conducting studies in such countries should provide important insights concerning the potential protective role of formal education and may allow us to tease apart the influence of education and cognitive ability. Preliminary evidence suggests that in the DRC, for children exposed to high levels of violence and interpersonal trauma, a secondary education reduces the level of PTSD symptoms, relative to a primary education, particularly for girls (Duagani Masika et al., 2019).
Altogether these results strongly support the conclusion that IQ and education affect the encoding or subsequent regulation of highly emotional events. Both IQ and education are critically related to the capacity for symbolic thinking, abstract reasoning, and decontextualized processing (Stanovich and West, 2000). The impact of trauma exposure may be more pronounced for individuals who have lower levels of cognitive abilities or limited access to the thinking tools developed through education. Several theoretical models of PTSD grant a central place to symbolic processing in the encoding of emotional experiences. This is what we review next.
PTSD models: cognitive function and PTSD
According to theoretical models of PTSD, higher level cognitive processes determine the nature of trauma memories. For example, Brewin’s (2014) and Dalgleish’s
(1999) theories of PTSD rest on the distinction between two modes of cognitive processing: a more abstract, symbolic, verbal, or propositional mode and a more perceptual, sensory, and associative mode. Intrusive memories are thought to result from an imbalance favouring the latter, leading to a more perceptual encoding of the traumatic event. Conversely, a more abstract encoding would result in less intrusive memories and less PTSD symptoms. Ehlers and Clark (2000) also base their analysis of PTSD on a dual pathways model of autobiographical memories. One path to encode memories relies on propositional knowledge and uses language or symbolic representations. This allows integration with other knowledge stored in semantic or autobiographical memory. The other path is based on associative memory and encodes more data-driven and implicit memory representations. Traumatic events may shift processing towards associative encoding. This can result in more intrusions, which are often evoked by non-semantic cues (temporal or perceptual) and generate disorganized sensory impressions, without explicit recollections or integration with other knowledge.
Thus, models suggest that symbolic processing has a strong impact on the encoding of the event and the integration of the memory trace in existing knowledge structures. Most models do not explicitly specify what will affect the extent of propositional vs. perceptual encoding. It could be hypothesized that situational factors (for instance, the current availability of cognitive resources) may play a role. Dispositional factors such as individual differences in symbolic cognitive ability, resulting from IQ or educational history, may also have an impact. Although the models do not explicitly draw this connection, the propositions are compatible with the empirical link between IQ, education and PTSD symptoms. However, IQ and education are not the unique determinants of symbolic processing. Experimental studies will be necessary to examine the causal role of symbolic processing in the encoding of emotional events.
5 Implications for understanding the 'normal' mind
We started this chapter by providing an overview of the prevalence of potentially traumatic events, events that pose a significant threat to a person’s safety and integrity and bring about intense feelings of fear, hopelessness, and terror. Statistically, the experience of trauma is quite common, hence completely in the realm of‘normal’ experiences. PTSD is much less frequent and only a minority of individuals exposed to trauma will develop PTSD.
In our review, we did not draw a sharp distinction between the effects of trauma exposure and those of PTSD. While it was not our goals to examine this systematically, our overview suggests that the effect of the two can often be similar in nature. Researchers oriented towards understanding individual differences will focus specifically on discerning the effects specifically related to PTSD. This requires experimental designs with three groups of participants: suffering from PTSD, exposed non-PTSD, and non-exposed healthy controls. While this is often difficult to achieve, an increasing number of studies present such a design. For some cognitive processes (attentional bias), these studies have provided evidence that effects of PTSD are stronger than those of trauma exposure (see, for example, Latack et al., 2017). The evidence is currently lacking for other processes such as reasoning and working memory. More studies are needed to provide an exhaustive portrait and to be able to determine where differences are merely quantitative and where there are qualitative differences. For our purpose, we conclude that both trauma exposure and PTSD are related to reasoning, working memory, and attention in important ways.
While trauma is ordinary in the statistical sense, it is extraordinary in the intensity of emotions associated. We can ask whether insights from the trauma studies help understand more ‘normal’ emotion-cognition interactions, those involving the milder, more mundane emotions ubiquitous in everyday life. We focus on three insights from trauma research that might have implications for ordinary emotional experiences: the role of relevance in emotional reasoning, the impact of symbolic reasoning on emotion encoding, and the mechanisms linking attention, working memory, and emotional reasoning.
Studies of reasoning and trauma have provided two important insights: trauma can decrease access to analytical reasoning, and the effect of emotion can be mitigated by personal relevance. The first point has been extensively supported in laboratory' studies. Inducing mild levels of emotion either through mood inductions (Oaksford et al., 2004) or by manipulating the emotional content (Blanchette, 2006) reduces analytic responses on a range of reasoning problems. This effect is linked to working memory load. In one study (Tremoliere et al., 2016), participants were given the dual task of maintaining visual matrices in working memory while they reasoned about emotional and neutral logical problems. Participants were slower on the working memory task when the reasoning contents were emotional, suggesting these problems had taken up a greater portion of available cognitive resources.
The second important insight is that relevance may modulate the effect of emotion on reasoning. We examined this experimentally in a study of deductive reasoning where we manipulated the emotional value and relevance of photographs presented along the reasoning problems (Blanchette et al., 2014). Drawing on the trauma studies, we hypothesized that emotional images might hinder analytic reasoning when they were irrelevant for the task, but not when they were relevant for the task. We reasoned that irrelevant emotional images would distract resources away from the inference-making process, but relevant images might help focus attentional resources on the task and support inference making. When the images were emotional but irrelevant, participants made more logical errors, compared to when the images were neutral. However, when the images were semantically related to the reasoning statements, emotional images did not lead to more errors. Response times were generally consistent with the hypothesized mechanism: emotional-unrelated images led to longer response times, but emotional-related images did not. This confirms that relevance may moderate the impact of milder emotional experiences on reasoning, similar to trauma.
Another important insight from trauma studies is that higher level cognitive processes affect the encoding of emotional experiences. This stems from research on the link between IQ, education, and PTSD symptoms, but also from the theoretical models of PTSD. To our knowledge, this has not been explored very much in experimental studies. We have started to do this in “trauma analogue” studies, in which participants view a video presenting shocking images that can lead to intrusions. We examine how the encoding of the emotional event is affected by (a) individual differences in cognitive ability, including WM and symbolic reasoning, and (b) experimental inductions of symbolic processing. In one study, we found that higher verbal abilities and WM capacities measured a priori were related to less intrusions and a reduced attentional bias following the trauma-analog video (Gregoire, Gagnon and Blanchette, in preparation). In an experimental study, we induced more symbolic processing in one group of participants using semantically distant, abstract analogies. Another group of participants processed more concrete analogies, which induced less symbolic processing. The abstract group showed reduced sensory encoding of the emotional video, as measured by evoked potentials (Leblanc-Sirois, Chouinard and Blanchette, submitted). This suggests that symbolic processing can have a causal impact on the way emotional events are encoded. This line of research is still in its infancy but exemplifies another insight from trauma studies that offers parallels to more ‘normal’ emotion-cognition interactions.
One final important insight concerns the consistency of the effect of trauma across functionally related cognitive processes. Trauma exposure and PTSD are negatively related to analytic or symbolic reasoning, working memory, and attentional control. There is a functional link between these three processes. Individual differences in WM and attentional control are highly correlated (Robison et al., 2018). Analytic reasoning processes heavily draw on WM resources. The causal link between these three functions is easy to imagine: depleted attentional control (particularly in conjunction with an attentional bias) leads to a loading of WM by irrelevant trauma-related stimuli which hinders analytic processing. This relationship would be moderated by the status of the distracters; when processing the trauma-related contents is relevant for the task, it would not have a deleterious effect. As far as we know, no experimental studies have yet examined this causal chain. This could be done using different methodologies acting on cognitive load and attentional control. The consistency of individual differences effects identified in the trauma studies suggests that this is a fruitful avenue to explore. It informs the initial sketch of a theoretical model we present shortly.
The trauma studies have thus generated interesting hypotheses to be explored in experimental studies. The correlational nature of the trauma and PTSD studies, bar a few exceptional prospective studies, makes it difficult to identify causal mechanisms. On the cognitive side, IQ is related to much more than symbolic processing abilities (speed of processing, confidence, occupational ‘success’, income, etc.). On the trauma side, exposure to potentially traumatic events is correlated with many other personal and socio-demographic variables (income, education, health, personality, etc.) that may all impact cognitive function. Experimental studies are necessary to disentangle these complex arrays of influence. Laboratory studies are usefi.il both for drawing implications for normal experience and for understanding the causal mechanisms at play in trauma.
Such studies can also help understand the mechanisms responsible for the effect of different psychological interventions. These most often necessitate symbolic processing. Clients need to put their experiences into words, which represents a first level of abstraction. With the help of their therapist, they will try to extract meaning from their experiences and reactions. Parts of this process can occur in expressive writing, where writing about negative painful experiences can have a positive impact on mental and physical health (Pennebaker, 1997). Using experimental studies, it will be possible to understand more precisely the mechanisms through which these interventions operate and maybe identify cognitive interventions that can increase symbolic processing and facilitate this process.
Beyond psychotherapeutic interventions, our work introduces the idea that cognitive interventions could help mitigate the affective impact of traumatic experiences. If symbolic thinking can be increased through education, then investing in education could act upon mental health following trauma exposure. This is an important idea to explore in post-conflict, often in low-income countries faced with challenges of reconstruction. In these situations, very high levels of PTSD are often documented and resources are scarce. Individual mental health services are often impossible, and it can be a challenge to develop a culturally appropriate model of intervention. Our work suggests that investing in education, apart from its numerous other positive effects, may also decrease psychopathological symptoms. Experimental studies are needed to establish the causal protective influence of education, and to identify the active cognitive ingredient, but this is a promising avenue for investigation.
A word of caution is needed when drawing parallels between studies conducted in high-income, often Western cultures, and those conducted in varied other cultures, often in low-income countries. This requires careful consideration of certain unquestioned methodological and theoretical assumptions. To highlight a few examples, there are immense challenges in determining the appropriate way to measure cognitive function and psychopathological symptoms. In our own work, for example, the ubiquitous use of computers and reaction times does not transfer easily to samples in Rwanda or the DRC, where many of our participants have never used a computer. Reading is not universal, especially in areas afflicted by violence, poverty, and instability, where access to education is difficult. Challenges with translation are abundant. More fundamentally, there are questions about the theoretical cross-cultural validity of constructs such as PTSD or intelligence. This points to the complexities of conducting such research in intercultural contexts; however, we believe this should not deter us from undertaking that challenge. If we want to understand the “normal” mind, our studies need to include the diversity of human contexts, cultures, and experiences. This is especially important in relation to trauma, as traumatic events disproportionately afflict individuals underrepresented in psychological research.
Altogether trauma studies can make an important contribution to understanding how higher level cognitive processes interact with emotion, both in high-intensity traumatic situations and in milder everyday emotional experiences, in both psychological disorder and healthy populations. We are still far from a comprehensive account of such interactions. Nevertheless, we draw together some elements to sketch a model that integrates these insights and provides a road map for our friture work.
6 Sketching a theoretical model
Existing models of PTSD provide detailed accounts of the ways in which higher level cognitive processing can influence the experience of trauma. To our knowledge, no model has yet been proposed to account for the reverse relation, between trauma and higher level cognition.
We suggest that exposure to highly emotional events generally leads to an attentional prioritization of threatening stimuli (attentional bias) (Buckley et al., 2000) coupled with facilitated memory activation for concepts related to these events, both in working memory, semantic memory, and episodic memory (Fal-setti et al., 2002). In the short term, this would result in intrusions (Verwoerd and Wessel, 2010) or ruminations. Ruminations are verbal thoughts about emotional events. This is likely to lead to a reduction in working memory capacity, as cognitive resources are partially allocated to the processing of trauma-related contents. This has immediate effects on all processes that require WM. Hence, trauma exposure and PTSD symptoms are likely to decrease the extent of symbolic or analytic reasoning, especially in contexts where the semantic contents of the task are irrelevant.
Individual differences can modulate this in important ways, notably differences in attentional control and WM capacity. Individuals who have a greater ability to inhibit the processing of task-irrelevant distracters, including intrusive trauma-related thoughts, would be less affected by trauma exposure. Furthermore, individuals with a greater propensity or capacity for symbolic encoding may also be less likely to experience intrusions in the first place. A more abstract encoding of the traumatic events should allow more contextualization of the memory trace in existing memory networks and mitigate the spontaneous activation of trauma-related thoughts (Sheppes et al., 2009). While individual differences in symbolic reasoning abilities may play an important role, situational factors may also promote a more abstract encoding or re-encoding of traumatic experiences (for instance, psychotherapy, expressive writing, etc.). Education, which develops abstract thinking and reasoning, could facilitate this process.
Human experience includes situations that evoke incomparable levels of emotions, emotions that signal a threat to the most basic human need to preserve safety and integrity. These situations occur in most people lives’, even is safe and prosperous countries. There are areas where these threats are numerous and recurrent. Some individuals will experience more chronic distress following such experiences, but everybody’s cognitive processes are likely to be altered by such experiences. Studying how these experiences shape higher level cognition provides a window into the mechanisms that link emotions and cognitive processes.
1 One recent meta-analysis has provided different conclusions, suggesting that the atten-tional bias towards threatening information in anxiety and PTSD is not significantly different from zero (Kruijt, Parsons & Fox, 2019). This meta-analysis however focused on the baseline data from RCT trials of a cognitive intervention aimed at modifying atten-tional bias in anxiety and PTSD. Of the 18 studies included, only 4 focused on PTSD. Furthermore, the analysis only included studies using the dot-probe task, ignoring the vast literature using the Emotional Stroop paradigm.
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