This study examined the moral dynamic of self-gain
vs other-welfare during
real and hypothetical conditions. Our behavioral results show that moral decisions with real
consequences diverge from hypothetical moral choices, verifying the ‘hypothetical
bias’ effect (
Kang et al., 2011).
Compared with imagining their moral actions, people who make moral decisions under real
conditions keep more money and inflict more pain on another subject. Although the research
exploring real moral action is limited (
Moll et al.,
2006;
Baumgartner et al., 2009;
Greene and Paxton, 2009), our results stand in
stark contrast to findings demonstrating that people act more morally than they think they
will (
Teper et al., 2011). Our results also
contradict the accumulated research illustrating a basic aversion to harming others (
Greene et al., 2001;
Cushman et al., 2012). We contend that this is likely due to the
fact that many of the moral scenarios used within the moral literature do not pit the
fundamental motivation of not harming others (physically or psychological) against that of
maximizing self-gain (
Haidt, 2007).
Accordingly, our findings reveal that engaging the complex motivations of
self-benefit—a force endemic to many moral decisions—can critically influence
moral action.
Our fMRI results identify a common neural network for real and hypothetical moral
cognition, as well as distinct circuitry specific to real and imagined moral choices. Moral
decisions—regardless of condition—activated the insula, MCC and dorsal TPJ,
areas essential in higher order social processes, such as empathy (
Singer et al., 2004). This neural circuitry is well instantiated
in the social neuroscience literature and fits with the findings that moral choices are
influenced by neural systems whose primary role is to facilitate cooperation (
Rilling and Sanfey, 2011). The TPJ has been
specifically implicated in decoding social cues, such as agency, intentionality and the
mental states of others (
Young and Saxe,
2008). For example, TPJ activation correlates with the extent to which
another’s intentions are taken into account (
Young and Saxe, 2009) and transiently disrupting TPJ activity leads to
interference with using mental state information to make moral judgments (
Young et al., 2010). Although there is a large
amount of research indicating that the TPJ codes for our ability to mentalize, there is also
evidence that the TPJ activates during attentional switching (
Mitchell, 2008). In addition, one study revealed that patients
with lesions to the TPJ do not show domain-specific deficits for false belief tasks (
Apperly et al., 2007). Although these differential
findings suggest that the specific functionality of the TPJ remains unclear, we propose that
TPJ engagement during real and imagined moral decisions suggests a similar mentalizing
process is at play in both real and hypothetical moral decision-making: when deciding how
much harm to apply to another, subjects may conscript a mental state representation of the
Receiver, allowing them to weigh up the potential consequences of their decision. This
neural finding reinforces the role of the TPJ—and thus the likely role of mental state
reasoning and inference—in moral reasoning.
However, we also found distinct neural signatures for both real and imagined moral
decisions. In line with the literature, hypothetical moral decisions were specifically
subserved by activations in the PCC and mPFC—regions also implicated in prospection,
by which abridged simulations of reality are generated (
Gilbert and Wilson, 2007). Although the overall pattern of brain
activation during these hypothetical moral decisions replicates the moral network identified
in previous research (
Greene et al., 2001),
the fact that the PCC and mPFC are activated both during prospection and during hypothetical
moral decision-making implies that this region is recruited for a wide spectrum of
imagination-based cognition (
Hassabis and Maguire,
2009). Thus, either hypothetical moral decisions and imagination share a similar
network or hypothetical moral decisions significantly rely on the imperfect systems of
prospection and imagination. Further research exploring whether the PCC and mPFC are
specific to hypothetical moral decisions, or recruited more generally for imagining future
events, would help clarify their roles within the moral network.
In contrast, real moral decisions differentially recruited the amygdala. These results are
consistent with the vast literature implicating the amygdala in processing social
evaluations (
Phelps, 2006), emotionally
relevant information (
Sander et al., 2003) and
salient stimuli (
Ewbank et al., 2009).
Research on moral cognition further implicates amygdala activation in response to aversive
moral phenomena (
Berthoz et al., 2006;
Kedia et al., 2008;
Glenn et al., 2009); however, this finding is not systematically
observed in moral paradigms (
Raine and Yang,
2006). In line with the literature, it is possible that in the Real PvG task the
amygdala is coding the aversive nature of the moral decision; however, distress ratings
indicated that both conditions were perceived as equally aversive. Accordingly, an
alternative interpretation is that the amygdala is monitoring the salience, relevance and
motivational significance (
Mitchell et al.,
2002) of the real moral choice space. Decisions, which produce real aversive
consequences (i.e. lose money or harm another), are far more salient and meaningful than
decisions that do not incur behaviorally relevant outcomes. The amygdala is also commonly
recruited for decisions which rely on social signals to emotionally learn positive and
negative associations (
Hooker et al., 2006).
It is possible that the amygdala activation found for real moral decisions is signaling
reinforcement expectancy information of both the positively (self-benefit) and negatively
(harm to another) valenced stimuli (
Blair,
2007), which then subsequently guides behavior (
Prevost et al., 2011). This theory not only accounts for the
differential behavioral findings between the real and hypothetical conditions but also it is
consistent with the more general theoretical consensus regarding human moral cognition
(
Moll et al., 2005), which emphasizes how
lower order regions like the amygdala modulate higher order rational processes (
Dalgleish, 2004).
Our fMRI results further indicate that there are dissociable neural mechanisms underlying
selfish and pro-social decisions. In the Real PvG, decisions that maximized financial
benefit (selfish decisions) correlated with activity in the OFC, dlPFC and
dACC—regions that support the integration of reward and value representations (
Schoenbaum and Roesch, 2005), specifically
monetary gain (
Holroyd et al., 2004) and loss
(
Bush et al., 2002). Furthermore, the dACC
was found to negatively correlate with empathic concern scores and positively correlate with
self-reported similarity ratings in the Real PvG task. Together, this suggests that the dACC
may be monitoring conflicting motive states (
Etkin et
al., 2011). However, the dACC has been further implicated in a variety of other
functions, including emotion regulation (
Etkin et
al., 2011), and weighing up different competing choices (
Mansouri et al., 2009). Thus, it is equally plausible that the
dACC is processing the conflicting negative emotions involved with choosing to harm another
for self-gain (
Amodio and Frith, 2006).
In the PvG task, the morally guided choice is to give up the money to prevent harm to
another. Unlike selfish decisions, such pro-social decisions showed significantly greater
activation in the rACC/mPFC and right temporal pole, demonstrating that the nature of real
moral decisions can be predicted by dissociable networks within the PFC. The rACC/mPFC is a
structure engaged in generating empathic feelings for in-group members (
Mathur et al., 2010) and for coding feelings of
altruistic guilt and distress during theory of mind tasks (
Fletcher et al., 1995). Clinical data have also shown that lesions
to this area stunt moral emotions, such as compassion, shame and guilt, and contribute to
overall deficits in emotional processing (
Mendez and
Shapira, 2009). In fact, research has demonstrated the rACC/mPFC as a region that
responds specifically to the aversion of not harming others (
Young and Dungan, 2011). Based on this, we propose that the
rACC/mPFC activation found for pro-social decisions could be attributed to the empathic
response generated by the emotional aversion (distress) of harming another—a key
motivational influence and proximate mechanism of altruistic behavior.
Theorists have pointed to the importance of studying moral cognition in ecological valid
and consequence-driven environments (
Casebeer,
2003;
Moll et al., 2005). Our results
illustrate that specific regions of the moral network subserve moral
choices—regardless of whether they are real or imagined. However, we also found a
divergence between real moral behavior and hypothetical moral intentions—which was
reflected in the recruitment of differential neurobiological systems. Thus, if morality is a
domain where situational influences and the impact of imminent, real consequences can sway
our decisions, then it is crucial that cognitive neuroscience investigate moral
decision-making under real conditions. This seems especially relevant in light of this new
neurobiological evidence, supporting what the philosopher Hume presciently
noted—‘the most lively thought is still inferior to the dullest sensation’
(
Hume, 1977).
1
,
2
Tim Dalgleish,
1
Russell Thompson,
1
Davy Evans,
1
,
2
Susanne Schweizer,
1
,
2
and Dean Mobbs
1
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