TBI versus non-TBI

A first important notion is that ABI refers to all types of brain damage that occur after birth which can have either a traumatic or non-traumatic aetiology (Lezak, Howieson, Bigler & Tranel, Reference Lezak, Howieson, Bigler and Tranel2012). Important distinctions between these two forms of ABI are the cause and the type of brain injuries that commonly occur. TBI is characterised by an injury to the brain caused by a forceful impact or sudden jolt to the head (Anderson, Bigler & Blatter, Reference Anderson, Bigler and Blatter1995; Levin & Kraus, Reference Levin and Kraus1994; Meythaler, Peduzzi, Eleftheriou & Novack, Reference Meythaler, Peduzzi, Eleftheriou and Novack2001). non-TBI are commonly the result of tumours, lesions, vascular malformations, anoxia or infections of the brain, often causing subarachnoid haemorrhages or other injuries (Teasell et al., Reference Teasell, Bayona, Marshall, Cullen, Bayley, Chundamala and Tu2007). Importantly, TBIs and non-TBIs do not lead to the same type of damage with respect to their location, typically, TBIs can cause widespread injury effects, whereas non-TBIs result in focal brain injuries. Moreover, since non-TBI has an internal cause, it cannot be ruled out that this by itself may have led to impairments in moral cognition. Among the nine studies in this review which included both types of ABI (i.e., TBI and non-TBI), one study (Ciaramelli, Braghittoni & di Pellegrino, Reference Ciaramelli, Braghittoni and di Pellegrino2012) found the same results after excluding people with TBI from analysis. In this study, the aim was to assess moral cognition in people with focal ventromedial prefrontal cortex (vmPFC) damage; however, the authors could not rule out additional diffuse axonal injury in other regions of the brain in the TBI sub-group. We did not encounter any article that directly compared moral impairments between people with TBI and people with non-TBI. In this regard, for future studies, it is important to report the injury aetiology, since there may be differences in the injury being focal or widespread. Furthermore, if a mix of both TBI and non-TBIs make up one sample, it is advisable to re-run the analysis on the TBI and non-TBI group separately to ensure that moral impairments do not differ between the two types of ABI.

The influence of different approaches to measure moral impairments in ABI

Across the 27 selected studies, ten different approaches (see Table 1) have been used to index moral cognition in ABI. Five of these approaches, across 21 studies, assessed the individuals’ ability to judge ‘moral dilemmas’. Despite the common use of moral dilemmas, the ten approaches we found in our search still differed in various ways. Before discussing these different measurement approaches, it is important to distinguish between different outcome measures of moral cognition. In this review, moral cognition is used as an umbrella term for the concepts moral decision-making, model reasoning and moral judgement. Moral decision making, which can be a decision about how to behave in a real or hypothetical moral dilemma (i.e., lie or tell the truth). Moral reasoning in the current review refers to the individual’s ability to give reasons for their decisions or judgements about social or moral behaviours (i.e., mature reasoning). Moral judgement refers to a judgement or evaluation about the moral acceptability of actions (e.g., judgement of moral character, estimating consequences or punishment allocation).

A key aspect that contributes to the differences in approaches used to measure moral cognition involves the content of the moral dilemmas. Moral dilemmas are focused on situations where there is a social problem that requires a response, this can include many a number of situations, such as, theft, property damage, dishonesty or harm to another person. The type of action that may or may not be carried out (i.e., the decision to be made) to resolve the social problem can vary in multiple ways, and this variation can affect how individuals respond. To better understand the importance of this issue, a distinction must be made between ‘universal moral dilemmas’ and ‘sociomoral dilemmas’. Universal moral dilemmas are those which describe a typical moral dilemma (e.g., stealing medication for a sick family member). Whereas sociomoral dilemmas involve scenarios that are likely experienced in daily life (e.g., being pressured by peers to break school rules). According to our findings, the literature on moral cognition in people with ABI is largely dominated by the use of universal moral dilemmas. Namely, 16 out of the 21 studies using moral dilemmas made use of universal moral dilemmas and five used sociomoral dilemmas. The way moral cognition is mapped out is fundamental to how moral impairments are perceived in people with ABI. For example, modifying the content of the scenario in this way can alter the personal involvement of the participant (Dooley, Beauchamp & Anderson, Reference Dooley, Beauchamp and Anderson2010). A large number of universal moral dilemmas used in the literature (i.e., the Heinz dilemma) are likely not realistic for the representative group. Therefore, although these scenarios may give insights into the processes involved in moral cognition, they provide limited insight into daily moral reasoning capabilities of the individuals; these skills are referred to as ‘sociomoral skills’ (Dooley et al., Reference Dooley, Beauchamp and Anderson2010; Haidt, Reference Haidt2001).

Aside from the overarching difference between universal moral dilemmas and sociomoral dilemmas, there are a number of other variations to the content of the dilemmas that alter how people with ABI respond. In nine of the studies where universal moral dilemmas were used, a distinction was made between ‘impersonal’ and ‘personal’ moral dilemmas. For example, in a scenario in which saving five lives requires one person to die, a personal moral dilemma is where the individual carrying out the action is directly involved in the production of harm (i.e., pushing a stranger off a bridge). An impersonal moral dilemma is where the individual carrying out the action is not directly involved in the production of harm (i.e., flipping a switch; Greene, Nystrom, Engell, Darley & Cohen, Reference Greene, Nystrom, Engell, Darley and Cohen2004; Greene, Sommerville, Nystrom, Darley & Cohen, Reference Greene, Sommerville, Nystrom, Darley and Cohen2001). Critically, whether the action in question is personal or impersonal has an impact on how individuals respond. Healthy individuals typically choose to permit the impersonal action, thereby saving multiple lives (i.e., utilitarian preference, which is defined as valuing actions that serve the aggregate welfare), whereas they typically choose to omit the personal action, thereby letting multiple people die (i.e., deontological preference, where the act is deemed right or wrong despite its consequences). Of the studies included in this review that assessed people with ABI on both personal and impersonal moral dilemmas, all except two (Craver et al., Reference Craver, Keven, Kwan, Kurczek, Duff and Rosenbaum2016; Ziaei, Togha, Rahimian & Persson, Reference Ziaei, Togha, Rahimian and Persson2019) found that people with ABI differ to healthy people in their responses to personal moral dilemmas; however, people with ABI and controls do not differ in their responses to impersonal moral dilemmas.

Similarly, the extremity of the scenario in universal moral dilemmas may impact how individuals respond. Kahane et al. (Reference Kahane, Wiech, Shackel, Farias, Savulescu and Tracey2012) found that in extreme dilemmas (e.g., where the action involves murder), healthy individuals’ intuitive response is to omit the act, thereby not saving the most lives. On the other hand, in a less extreme scenario (e.g., where the action involves lying), healthy individuals intuitively choose to permit the act. One study made use of the distinction between extreme and less extreme dilemma’s and presented them to people with ABI (Rowley, Rogish, Alexander & Riggs, Reference Rowley, Rogish, Alexander and Riggs2018). They found that the intuitiveness of the moral dilemma determined how people with ABI respond. The ABI group responded counterintuitively to both extreme and less extreme dilemmas (i.e., oppositely to healthy individuals).

Aside from the content of moral dilemmas, a task characteristic which also relates to the individuals personal involvement in the dilemma includes the framing of the question in the dilemma. For example, after presenting individuals with a dilemma, there are a number of ways to ask the individual whether they should or should not endorse the action presented in the scenario. We observed that the phrasing of this question is not consistent across studies. Two examples are, ‘What would you do?’ versus ‘What should you do?’. The former being a reflection of a personal standard, while the latter reflects awareness of a societal standard. This seemingly minor difference could alter the individual’s personal involvement in the dilemma, through a switch to the first-person perspective, and thus, affect their behavioural responses.

Another task characteristic which likely plays an important role in the assessment of moral cognition in people with ABI concerns the mode of task presentation. A number of studies presented ABI groups with lengthy written scenarios; meanwhile, other studies presented dilemmas using pictures, cartoons or virtual reality (see Table 1 for an overview of the different approaches used to assess moral cognition in ABI). Impairments in other cognitive domains, such as attention or working memory, needed to perform the task, may influence peoples’ responses. For example, the studies that assessed adolescents with ABI typically used picture scenarios and found less consistent differences between ABI groups and non-ABI groups (e.g., Beauchamp et al., Reference Beauchamp, Dooley and Anderson2013; Dooley et al., Reference Dooley, Beauchamp and Anderson2010). Though it is possible that an ABI occuring during adolescence results in less severe moral impairments, it cannot be ruled out that the task modality may play a role in the individual’s ability to visualise the scenario. Given that no study has systematically compared different task modalities to examine how this effects moral cognition in people with ABI, this may be an opportunity for future research.

Lastly, studies in which the age of onset of ABI was the primary interest (n = 11) used moral dilemmas to assess individuals’ moral maturity. Among these studies, the most important outcome variable was individuals’ moral reasoning, that is, the justification of the decision made in the moral dilemma. Studies in which the focus of investigation was the location of the ABI (i.e., studies in people with focal ABI; n = 13) typically assessed moral decision making, that is, the choice of which action to permit in the moral dilemma rather than moral reasoning. Consequently, different outcome measures (i.e., moral reasoning and moral decision making) were used to assess different ABI groups (i.e., age of onset ABI and focal ABI groups), making it almost impossible to compare moral cognition between these types of studies.

In sum, the content of moral dilemmas and the tools used to present these dilemmas play a crucial role in how people with ABI respond and therefore affect the interpretation of the extent of their impairments. Notably, since the extremity of the scenario impacts how people with ABI respond (Rowley et al., Reference Rowley, Rogish, Alexander and Riggs2018), the common use of universal moral dilemmas, which often contain extreme and sometimes unrealistic scenario’s, may not be an optimal measurement tool to assess moral cognition in people with ABI. For example, future research should focus on whether people with ABI respond differently to universal moral dilemmas versus sociomoral dilemmas. Additionally, for treatment and intervention purposes, further research must be carried out assessing the sociomoral skills between different age groups of people with ABI using age-appropriate, realistic scenarios.

The role of age at onset of ABI on moral cognition

There are 11 studies that have investigated how the age of onset of an ABI affects moral cognition. All 11 studies assessed moral maturity using or referring to Kohlberg’s model (Kohlberg, Reference Kohlberg1971, Reference Kohlberg1974), which includes three levels of moral maturity. In these studies, people are presented with a scenario in which there is a conflict between two moral imperatives and then asked to describe the protagonist’s actions and their reasoning through a series of questions. For example, a scenario where a poor young man steals an expensive drug from a greedy pharmacist in order to save the life of his dying wife. The reasoning behind peoples’ responses is indicative of their moral maturity. Three case studies and one group study inluded in this review tested moral reasoning in people who experienced an ABI at an early age (Anderson, Bechara, Damasio, Tranel & Damasio, Reference Anderson, Bechara, Damasio, Tranel and Damasio1999; Grattan & Eslinger, Reference Grattan and Eslinger1992; Price, Daffner, Stowe & Mesulam, Reference Price, Daffner, Stowe and Mesulam1990). The people with the earliest occurring injuries, at 7 days, 4 years (Price et al., Reference Price, Daffner, Stowe and Mesulam1990), 3 months and 15 months (Anderson et al., Reference Anderson, Bechara, Damasio, Tranel and Damasio1999) all responded at the lowest level (Level 1) of moral maturity. This level is characteristic of moral reasoning of most healthy children under the age of 9, even though all of these people were at adult age during testing. Children in which the ABI occurred later, at 7 years old in a case study (Grattan & Eslinger, Reference Grattan and Eslinger1992) or under the age of 13 in one group study (n = 16; Couper, Jacobs & Anderson, Reference Couper, Jacobs and Anderson2002) were able to reason at a slightly higher level of moral maturity (Level 2). This level is typically achieved by most healthy children aged 10–13 years. At the time of testing, the 7-year-old case study was 33 years old; however, the children in the group study were still children/young adolescents. In a direct comparison to healthy children, Couper et al. (Reference Couper, Jacobs and Anderson2002) found that children diagnosed with ABI responded with significantly lower levels of moral maturity with almost every person scoring lower than similarly aged healthy children. In sum, early-onset ABI (< 13 years old) leads to impaired moral reasoning, despite being tested at a later age. These people, due to early brain damage, may have never acquired the socially relevant knowledge necessary for appropriate moral behaviour. From these four studies, a trend of increasing moral maturity in persons with later ABI onset is apparent. It is therefore possible that moral maturity could develop at a later stage before adulthood and that injuries occurring during adolescence may not result in such impairments.

Four studies included in this review investigated people who suffered ABI during adolescence (Beauchamp et al., Reference Beauchamp, Dooley and Anderson2013, Reference Beauchamp, Vera-Estay, Morasse, Anderson and Dooley2019; Cook et al., Reference Cook, Hanten, Orsten, Chapman, Li, Wilde and Levin2013; Dooley et al., Reference Dooley, Beauchamp and Anderson2010). A newly developed task (‘So-moral’ and ‘So-mature’) was used in three studies (Dooley et al., Reference Dooley, Beauchamp and Anderson2010). This task was created specifically for understanding moral maturity in adolescents and used age-appropriate, daily moral reasoning scenarios, such as ‘cheating in a game of pool’, also known as sociomoral dilemmas. The So-moral component of the task measures the decision (e.g., ‘Would you cheat?’). The So-mature component measures the reasoning of that decision. This second measure is used to indicate the individuals’ moral maturity. Three studies compared the performance of adolescents with TBI to age-matched healthy controls on this task. In one study (Dooley et al., Reference Dooley, Beauchamp and Anderson2010), a group of adolescents (n = 25) with a history of (mostly mild) TBI scored within Level 2, which was not significantly different from age-matched controls and is indicative of their age according to the model. We related the scores reported in Dooley et al. (Reference Dooley, Beauchamp and Anderson2010) to Kohlberg’s model based on the cut-off scores given in Beauchamp et al. (Reference Beauchamp, Dooley and Anderson2013). In Beauchamp et al. (Reference Beauchamp, Dooley and Anderson2013), a group of adolescents (n = 25) with a mix of both moderate-severe and mild TBIs responded with different levels of moral maturity. Adolescents with moderate-severe TBIs responded at level 1, whereas the mild TBI group maintained an overall maturity level comparable to a healthy control group at level 2. These results suggest the severity of the TBI to be an important factor in determining moral maturity. The most recent study (Beauchamp et al., Reference Beauchamp, Vera-Estay, Morasse, Anderson and Dooley2019) investigated a larger group of adolescents with TBIs (n = 43) and reported that the TBI group scored significantly lower on the moral maturity task compared to age-matched controls, regardless of the severity of the TBI. In this study, performance was scored differently to the other adolescent studies previously mentioned, and moral maturity could not be assessed according to Kohlberg’s model. Two of the three studies (Beauchamp et al., Reference Beauchamp, Dooley and Anderson2013, Reference Beauchamp, Vera-Estay, Morasse, Anderson and Dooley2019) also reported the scores on the decision-making component of the task. Interestingly, these results indicate that adolescents with ABI deviate less from healthy controls on the decision-making component compared to the reasoning component. The fourth study (Cook et al., Reference Cook, Hanten, Orsten, Chapman, Li, Wilde and Levin2013) used a novel virtual-reality task to assess adolescents with TBIs on two types of dilemmas: legal dilemmas (e.g., endorsing underage drinking) and sociomoral dilemmas (e.g., using a friend’s answers to cheat on a test). The TBI group provided a comparable amount of short-term consequences as the control group, however, fewer long-term consequences in cases of sociomoral dilemmas.

In sum, these studies together show mixed results as to whether there is an impairment in moral decision-making and moral reasoning when the ABI occurred during adolescence and whether the injury was severe or not. Together, these four adolescent studies present the possibility that adolescents with ABI may know what they need to do in sociomoral scenarios, however, cannot offer adequate reasoning for their decision. Moreover, all adolescent studies carried out testing while the people were still adolescents, compared to most early-onset studies that tested the people while in adulthood. This means that, in the case of impaired moral cognition, it is not clear whether adolescents with ABI remain at the same level of moral maturity through to adulthood. Moreover, in contrast to the early-onset studies, the exact age of onset of individuals in the sample was not reported, and this factor has not been considered in the analysis.

In two studies (Chiasson, Elkaim, Weil, Crevier & Beauchamp, Reference Chiasson, Elkaim, Weil, Crevier and Beauchamp2017; Taber-Thomas et al., Reference Taber-Thomas, Asp, Koenigs, Sutterer, Anderson and Tranel2014), the patient sample was made up of individuals where the onset occurred both before adolescence and during adolescence. Interestingly, both took the age of onset into account in their analysis and found that the earlier the injury occurred, the more moral maturity was hampered. This is inline with the early-onset and adolescent onset studies showing that the age of onset of the injury is crucial to the impairments in moral maturity.

Finally, we found two studies that investigated moral cognition in people who suffered ABI during adulthood. If impairments in moral cognition are solely caused by early acquired injuries, therefore hampering development, then there should not be an impairment when the injury occurs in adulthood. Evidence for this notion comes from a case study (Saver & Damasio, Reference Saver and Damasio1991) and a group study (n = 6; Anderson et al., Reference Anderson, Bechara, Damasio, Tranel and Damasio1999) in which all of the people with ABI judged moral dilemmas at the either level 2 or level 3 of Kohlberg’s model, thus suggesting preserved moral maturity. Together, these studies indicate that people with adult-onset ABI reach moral maturity stages comparable to healthy controls.

The role of location of ABI in moral cognition

We encountered 13 articles where people with focal ABI were studied. Among these, nine studies assessed people with damage to the vmPFC, two studies assessed people with bilateral injuries to the hippocampus, one study included people with vmPFC and people with hippocampal lesions and one study assessed people with right frontopolar cortex lesions (rFPC). A further four studies were found which assessed people with widespread ABI.

Early neuroimaging studies have shown correlational evidence for the role of the vmPFC in moral cognition. Specifically during personal moral dilemmas, participants who showed vmPFC activity were more likely to condemn the personal act (i.e., to not push the stranger; Greene et al., Reference Greene, Sommerville, Nystrom, Darley and Cohen2001, Reference Greene, Nystrom, Engell, Darley and Cohen2004) and therefore show a deontological preference in these dilemmas. Five studies in this review directly tested the role of the vmPFC in moral decision-making (Ciaramelli, Muccioli, Làdavas & Di Pellegrino, Reference Ciaramelli, Muccioli, Làdavas and Di Pellegrino2007; Koenigs et al., Reference Koenigs, Young, Adolphs, Tranel, Cushman, Hauser and Damasio2007; Moretto, Làdavas, Mattioli & Di Pellegrino, Reference Moretto, Làdavas, Mattioli and Di Pellegrino2010; Taber-Thomas et al., Reference Taber-Thomas, Asp, Koenigs, Sutterer, Anderson and Tranel2014; Thomas, Croft & Tranel, Reference Thomas, Croft and Tranel2011). In these studies, responses from healthy individuals and/or non-vmPFC brain-damaged controls were compared with the responses of people with vmPFC damage on moral dilemmas. Inline with the existing literature on moral decision-making, the control groups always showed a deontological preference (i.e., choosing not to endorse the act and not maximize the aggregate welfare) in personal moral dilemmas (i.e., when the act involves directly harming someone). Across all five studies, however, people with vmPFC damage consistently showed the opposite preference to the control groups in personal moral dilemmas, indicating these violations to be more acceptable and opting to maximize the aggregate welfare (i.e., utilitarian preference).

According to Koenigs et al. (Reference Koenigs, Young, Adolphs, Tranel, Cushman, Hauser and Damasio2007), the responses of the ABI group differed to controls predominantly in dilemmas where healthy individuals responded slower and with lower agreement (i.e., ‘high-conflict’ dilemmas). Moretto et al. (Reference Moretto, Làdavas, Mattioli and Di Pellegrino2010) showed that a lack of sympathetic arousal (measured with skin-conductance responses) in people with vmPFC damage in response to moral dilemmas may contribute to these atypical moral responses. This abnormal response persisted in people with ABI, even when the directness and perspective of the dilemmas were altered (Thomas et al., Reference Thomas, Croft and Tranel2011). For example, where the person on the sidetrack is your daughter (directness), or when the act is carried out by them, or someone else (perspective). Lastly, further support for abnormal moral preferences, particularly in early-onset cases, comes from a comparison study of the people with adult-onset ABI from Koenigs et al. (Reference Koenigs, Young, Adolphs, Tranel, Cushman, Hauser and Damasio2007) with a group of early/adolescent-onset vmPFC-damaged people (Taber-Thomas et al., Reference Taber-Thomas, Asp, Koenigs, Sutterer, Anderson and Tranel2014). Dividing dilemmas into ‘self-serving’ and ‘non-self-serving’ scenarios, results showed that the people with developmental-onset ABI displayed the same abnormal preferences in personal moral dilemmas (i.e., utilitarian preference), however, that they also endorsed significantly more ‘self-serving’ dilemmas compared to the adult-onset group, demonstrating abnormally egocentric moral judgements, which, according to Kohlberg’s model, falls inline with lower levels of moral reasoning.

In sum, damage to the vmPFC results in a utilitarian preferences by placing more weight on the outcome of the scenario than the action itself in moral dilemmas. However, according to these studies, this preference only deviates from healthy controls under certain conditions, such as when the dilemmas are deemed ‘personal dilemmas’. Contrary to this claim, however, Rowley et al. (Reference Rowley, Rogish, Alexander and Riggs2018) raises the possibility that moral dilemmas are characterised as either ‘intuitively utilitarian’ or ‘intuitively deontological’, having found that people with widespread ABIs responded with an overall counterintuitive bias. This study shows that the responses of people with ABI may largely depend on the nature of the scenario (i.e., being extreme or less extreme) and highlights the importance of the content of the moral dilemmas as a determining task characteristic.

Similar moral decision-making preferences were observed in two studies that assessed people with widespread ABI, where they showed a utilitarian preference on personal moral dilemmas (Martins, Faisca, Esteves, Muresan & Reis, Reference Martins, Faisca, Esteves, Muresan and Reis2012; Njomboro, Humphreys & Deb, Reference Njomboro, Humphreys and Deb2014). Njomboro et al. (Reference Njomboro, Humphreys and Deb2014) also examined people who suffered widespread ABI while experiencing apathy symptoms, measured via caregivers’ responses to the Apathy Evaluation Scale (Marin, Biedrzycki & Firinciogullari, Reference Marin, Biedrzycki and Firinciogullari1991). Scores above 41 on this scale indicated the presence of apathy in these people, with this group showing stronger utilitarian preferences in response to personal moral dilemmas compared to people with ABI with no apathy. It is possible that the people in these studies suffered damage to the vmPFC as well as other regions; however, the exact location of injuries is not reported.

A further four studies in people with vmPFC damage assessed different aspects of moral cognition compared to the previously mentioned studies and therefore they are discussed separately. Two of these studies investigated whether individuals with damage to the vmPFC process harmful intent differently to healthy individuals (Ciaramelli et al., Reference Ciaramelli, Braghittoni and di Pellegrino2012; Young et al., Reference Young, Bechara, Tranel, Damasio, Hauser and Damasio2010). When we attempt to understand and evaluate others actions, we may question, for example, whether they intended to cause harm. To disentangle the contribution of intentions (e.g., actions carried out in order to reach a goal) and outcomes (e.g., the consequences of the action) to moral judgement in people with vmPFC damage, both studies manipulated the intention of the moral agent and the outcomes of that action. The comparison control groups for these studies were also healthy individuals and/or non-vmPFC brain-damaged controls. Inline with the expectation that vmPFC damaged people place more weight on the outcome of the scenario than the action itself (i.e., utilitarian vs. deontological), both studies found that individuals with vmPFC damage judged a failed attempt to harm as more permissible (Ciaramelli et al., Reference Ciaramelli, Braghittoni and di Pellegrino2012; Young et al., Reference Young, Bechara, Tranel, Damasio, Hauser and Damasio2010) and accidental harm as less permissible (Ciaramelli et al., Reference Ciaramelli, Braghittoni and di Pellegrino2012) than controls. This means that people with vmPFC damage do not place weight on the intention when making a moral judgement of others’ actions that are potentially harmful. An individual, therefore, who accidentally harms someone may be more harshly condemned by vmPFC damaged people than an individual who attempts to harm someone but fails at doing so. Relatedly, Asp and colleagues (Reference Asp, Gullickson, Warner, Koscik, Denburg and Tranel2019) sought to understand the role of the vmPFC in ‘third-party punishment’, which is a behavioural component involving punishment allocation. Third-party punishment is when a participant observes moral violations and can punish the violating person (i.e., allocating lesser punishment for accidental, non-violent crimes or greater punishment for intended, violent crimes). The fact that third-party punishment is altruistic (i.e., meaning that it is costly to the punisher and does not result in direct benefits) suggests that motivation for justice or fairness plays a big role, closely linking it with morality. In accordance with the previous findings (Ciaramelli et al., Reference Ciaramelli, Braghittoni and di Pellegrino2012; Young et al., Reference Young, Bechara, Tranel, Damasio, Hauser and Damasio2010), people with vmPFC damage assigned more lenient punishments to criminals that committed violent crimes, whereas punishments allocated to criminals that committed non-violent crimes were equal to healthy controls (Asp et al., Reference Asp, Gullickson, Warner, Koscik, Denburg and Tranel2019). This study provides evidence for deficits in the moral act of third-party punishment among people with vmPFC ABI.

Vascello and colleagues (Reference Vascello, Marchetti, Scaltritti, Altoè, Spada, Molinero and Manfrinati2018) found that people with widespread ABIs more easily endorsed moral violations than ‘socio-conventional transgressions’, which involve a violation of convention without the involvement of harm, injustice or rights violations; those that do include these refer to moral violations (Vascello et al., Reference Vascello, Marchetti, Scaltritti, Altoè, Spada, Molinero and Manfrinati2018). Lastly, a study investigated how people with vmPFC damage differ in their spontaneous, unintentional judgements about moral actions, termed, implicit moral judgement (Cameron, Reber, Spring & Tranel, Reference Cameron, Reber, Spring and Tranel2018). In this study, participants made rapid moral judgements to different types of words (morally wrong words, e.g., genocide, non-moral negative words, e.g., rejection and, neutral words, e.g., agreement). A distractor word was presented for 100 ms after a target word. The participants responded about whether the target word was morally wrong. Through measuring the number of errors, the authors clarified three possible processes driving judgement throughout the task: intentional judgement, unintentional judgement or response bias. People with vmPFC damage exhibited reduced unintentional judgement as well as lower intentional judgements overall. These findings did not generalize to negative or neutral words, suggesting this was not a domain-general affective deficit. In sum, the study suggests a dual deficit in not only intentional moral judgement (Ciaramelli et al., Reference Ciaramelli, Muccioli, Làdavas and Di Pellegrino2007; Koenigs et al., Reference Koenigs, Young, Adolphs, Tranel, Cushman, Hauser and Damasio2007; Martins et al., Reference Martins, Faisca, Esteves, Muresan and Reis2012; Moretto et al., Reference Moretto, Làdavas, Mattioli and Di Pellegrino2010; Njomboro et al., Reference Njomboro, Humphreys and Deb2014; Taber-Thomas et al., Reference Taber-Thomas, Asp, Koenigs, Sutterer, Anderson and Tranel2014; Thomas et al., Reference Thomas, Croft and Tranel2011; Vascello et al., Reference Vascello, Marchetti, Scaltritti, Altoè, Spada, Molinero and Manfrinati2018) but also unintentional moral judgements in individuals with focal vmPFC ABIs (Cameron et al., Reference Cameron, Reber, Spring and Tranel2018).

The hippocampus is a brain structure critical for supporting cognitive functions such as declarative memory (Tulving & Markowitsch, Reference Tulving and Markowitsch1998). Declarative memory may contribute to judgements on moral dilemmas. Namely, scene construction, a critical aspect of moral reasoning, relies on our ability to recollect past experiences and integrate relevant information and is known to rely on the hippocampus (Addis, Wong & Schacter, Reference Addis, Wong and Schacter2007). The ability to visualise scenes may be compromised in people with hippocampal lesions; therefore, moral reasoning may also be altered. From our literature search, we encountered two studies that assessed moral decision-making in people with hippocampal damage.

Contrary to individuals with vmPFC lesions as shown in other studies, who tend to show a preference for utilitarian choices in (high-conflict) personal moral dilemmas, one study (McCormick, Rosenthal, Miller & Maguire, Reference McCormick, Rosenthal, Miller and Maguire2016) found that people with hippocampal lesions more often chose to omit the act (i.e., deontological preference) in high-conflict personal moral dilemmas. Interestingly, the hippocampal ABI groups indicated via subjective reports that their decisions were heavily influenced by an initial adverse emotional response to the task (e.g., having to kill somebody), rather than overcoming this response and visualising the bigger picture of saving the most lives. This inability to visualise the scene may stem from declarative memory deficits present in these people. High levels of sympathetic arousal (measured using skin-conductance responses) in people with hippocampal lesions during decision-making corroborated the subjective reports that these people experienced greater emotional responses to moral dilemmas in comparison to controls. Contrary to these results, Craver et al. (Reference Craver, Keven, Kwan, Kurczek, Duff and Rosenbaum2016) suggest that people with hippocampal lesions do not differ to healthy individuals in their moral judgements, finding that both groups exhibited similar patterns in moral preferences, with a deontological preference in personal moral dilemmas, however, not an exaggerated deontological bias as was found by McCormick et al. (Reference McCormick, Rosenthal, Miller and Maguire2016). Both studies (Craver et al., Reference Craver, Keven, Kwan, Kurczek, Duff and Rosenbaum2016; McCormick et al., Reference McCormick, Rosenthal, Miller and Maguire2016) used written text as the mode of stimulus presentation. Crucially, if the use of text-based stimuli contributes to the observed exaggerated deontological responses in individuals with hippocampal damage (McCormick et al., Reference McCormick, Rosenthal, Miller and Maguire2016), by impaired ability to visualise the scene, then providing visual stimuli (i.e., pictures, videos), instead of text-based stimuli, could alter the moral decisions of these individuals.

Lastly, one study (Croft et al., Reference Croft, Duff, Kovach, Anderson, Adolphs and Tranel2010) assessed ‘moral-updating’, which is the process of updating character judgements of others, based on observing them engage in social and moral behaviours, in both people with hippocampal lesions and people with vmPFC lesions. Individuals with vmPFC damage demonstrated reduced moral updating, this means that despite learning about morally bad behaviour from a person, these individuals would still believe the person to be moral. People with hippocampal lesions, however, showed the opposite change, generating exaggerated moral updating, meaning they would more likely change their judgements about a person’s moral character in response to observing morally relevant behaviours. These findings support the notion that a possible consequence of the declarative memory deficits present in individuals with hippocampal lesions (i.e., not being able to visualise the whole scene in their head) may result in overvaluing emotional input, thereby leading to increased moral updating. This final study demonstrates the different preferences observed in people with vmPFC and hippocampal ABI. Low rates of moral updating as observed in people with vmPFC damage falls inline with these individuals showing exaggerated utilitarian preferences, whereby the action itself is not heavily judged, but rather the outcome (Ciaramelli et al., 2007; Reference Ciaramelli, Braghittoni and di Pellegrino2012, Koenigs et al., Reference Koenigs, Young, Adolphs, Tranel, Cushman, Hauser and Damasio2007; Moretto et al., Reference Moretto, Làdavas, Mattioli and Di Pellegrino2010; Taber-Thomas et al., Reference Taber-Thomas, Asp, Koenigs, Sutterer, Anderson and Tranel2014; Thomas et al., Reference Thomas, Croft and Tranel2011; Young et al., Reference Young, Bechara, Tranel, Damasio, Hauser and Damasio2010). Relative to this, increased moral updating falls in line with individuals with hippocampal lesions showing exaggerated deontological preferences, whereby the moral action is more harshly judged (McCormick et al., Reference McCormick, Rosenthal, Miller and Maguire2016).

Besides the vmPFC and hippocampus, the rPFC has been considered to play a role in processes that contribute to moral judgements. A recent study (Ziaei et al., Reference Ziaei, Togha, Rahimian and Persson2019) explored the causal role of the rFPC in moral judgements by comparing responses to personal and impersonal moral dilemmas (Greene et al., Reference Greene, Sommerville, Nystrom, Darley and Cohen2001) in people with rFPC damage and healthy controls. Emotions were induced prior to making these judgements by showing participants neutral or emotional pictures. The two groups did not differ in utilitarian preferences nor in reaction time for personal or impersonal moral dilemmas. Furthermore, both groups were similarly affected by the emotion induction, providing more utilitarian responses to personal and impersonal moral dilemmas following negative pictures. These results give proof of the fact that neural processes contributing to normal moral judgement do not crucially depend on the rFPC, since moral judgements were intact in individuals with focal rFPC damage (Ziaei et al., Reference Ziaei, Togha, Rahimian and Persson2019).