- Email: [email protected]
Cultural Neuroscience of Moral Reasoning and Decision-Making
C H A P T E R
14 Cultural Neuroscience of Moral Reasoning and Decision-Making Yi-Yuan Tang1, Rongxiang Tang2 1Presidential
Endowed Chair in Neuroscience, Department of Psychological Sciences, Texas Tech University, Lubbock, TX, USA; 2Department of Psychology, Washington University, St. Louis, MO, USA
O U T L I N E 1. Introduction 281 1.1 Abstract Thinking/Reasoning—Arithmetic Processing281 1.2 Moral Reasoning/Decision-Making—Moral Dilemmas283
1. INTRODUCTION Research in cultural neuroscience examines how cultural and genetic diversity shape the human mind, brain, and behavior using a variety of multimodal methods.1 Cultural differences in understanding and conceptualizing one’s relationships with others may have led to diverse cultural systems for interpreting, thinking, reasoning, and decision-making about the world. Eastern holistic systems of thought rely on connectedness and relations as a primary way of understanding the world, whereas Western analytic systems of thought rely on discreteness as an epistemological way of thinking.2 Reasoning and decision-making, as important aspects of human high-level cognition, may be influenced by cultural differences. For example, Eastern Asians tend to frame the decision to help as a matter of moral responsibility, whereas Americans are more likely to frame it as one’s personal choice.3 Previous studies indicate that from attention and cognition to social cognitive processes, neural systems have likewise adapted differently across cultural contexts to facilitate divergent systems of social interactions and
Neuroimaging Personality, Social Cognition, and Character http://dx.doi.org/10.1016/B978-0-12-800935-2.00014-2
2. Concluding Remarks
286
Acknowledgment286 References286
relations.4 In this chapter, we will focus on the cultural differences in high-level cognition (moral reasoning and decision-making), especially between the Chinese and American cultures. We will explore the associated brain networks of cultural variation involved in these processes and will take abstract thinking/reasoning and moral decision-making as examples to demonstrate the neural basis of cultural influences on these processes that involve Eastern and Western cultures. This focus reflects the current growing theoretical and experimental curiosity among behavioral scientists and neuroscientists, as well as the general public.5 We acknowledge that this chapter provides an incomplete view of the literature on moral reasoning and decision-making.
1.1 Abstract Thinking/Reasoning—Arithmetic Processing Arithmetic or math processing often involves abstract thinking/reasoning. One example of a higher cognitive function that may be influenced by holistic vs. analytic thinking styles involves discrete neural patterns of arithmetic processing
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in Chinese and Westerners.5 The universal use of Arabic numbers in mathematics raises the question of whether they are processed the same way in people from different cultures who speak different languages, such as Chinese and English. To address this question, researchers used functional Magnetic Resonance Imaging (fMRI) to scan 12 native Chinese speakers (NCS) and 12 native English speakers (NES) who possessed a college-level education. The participants were instructed to perform four tasks during the scanning (see Figure 1 for examples): (1) the symbol condition: judge the spatial orientation of nonnumerical stimuli in which a triplet of nonsemantic characters or symbols are visually presented either in an upright or in an italic orientation. The task was to decide whether the third symbol had the same orientation as the first two; (2) the number condition: judge the spatial orientation of numerical stimuli, using the same task as in the symbol condition except for using Arabic digits as visual stimuli; (3) the addition condition: determine whether the third digit was equal to the sum of the first two in a triplet of Arabic numbers; and (4) the comparison condition: determine whether the third digit was larger than the larger of the first two in a triplet of Arabic numbers. A baseline condition of matching white and/ or gray circular dots was used to control for the motor and nonspecific visual components of the tasks. Results indicated a different cortical representation of numbers between native Chinese speakers and native English speakers. While the English speakers employed a language process relying on the left perisylvian cortices for mental calculation, such as a simple addition task, the Chinese speakers instead engaged a visuo–premotor association network for the same task (see Figure 1). We further chose two regions of interest, the perisylvian area, including both the Broca (Br) and Wernicke (Wn) areas, and the premotor association area between BA6, BA8, and BA9.6 Quantitative analyses were conducted by comparing the fMRI signal between the English and Chinese groups. We found the perisylvian activations were significantly larger in the English speakers than in the Chinese speakers (Figure 2(A)). As the arithmetic complexity increased across the four conditions (Symbol < Number < Addition < Comparison), there was a trend toward increased premotor activation in the Chinese speakers, but not in the English speakers (Figure 2(B)). Therefore, there was a double dissociation in brain activation between these two groups during these tasks, supporting clear cultural differences in the processing of numbers. In addition, for both cultural groups, the inferior parietal cortex was activated in the numerical quantity comparison. However, the fMRI connectivity analyses6 revealed a difference in the brain networks involved in the task for Chinese and English speakers. Two distinct patterns were observed in the functional networks: there was dorsal visuo-pathway dominance
(A)
(B)
(C)
(D)
FIGURE 1 Dissociation in the brain representation of Arabic numbers between native Chinese speakers (NCS) and native English speakers (NES). (A) During the symbol task in NCS. (B) During the number task in NCS. (C) During the symbol task in NES. (D) During the number task in NES. The task-dependent brain activation was determined by Statistical Parametric Mapping (SPM) by using a liberal threshold (p < 0.05) for illustrating a global pattern of the fMRI blood-oxygen-level dependent (BOLD) signal changes. The type-I error of detecting the difference was corrected for the number of resolution elements at each of the activated brain regions defined anatomically by using the SPM add-on toolbox automated anatomical labeling (AAL). The multiple comparison correction is the small volume correction (SVC) procedure implemented in SPM. (A and B) Examples of the visual stimuli used for the symbol task and the number task, respectively, are shown at the top. LH = left hemisphere; RH = right hemisphere; Br = Broca area; Wn = Wernicke area.
(through the parietal–occipital cortex) for the Chinese speakers, but ventral visuo-pathway dominance (through the temporal cortex) for the English speakers. Our findings have two implications. First, in both Chinese and English speakers, there is cortical dissociation between addition and numerical comparison processing. The addition task seems to be more dependent upon language processing than does the comparison task, which is consistent with the notion that there
V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
1. Introduction
283
FIGURE 2 Comparison of the activation intensity between native Chinese speakers (NCS) and native English speakers (NES) in the perisylvian language region (A) and the premotor association area (PMA) (B). The brain activation maps (left) were determined by contrasting BOLD signals between NCS and NES only during the comparison task, with the NES group showing relative increase of the signal (A, English > Chinese), and the NCS group showing relative increase of the signal (B, Chinese > English). The within-group task-dependent activation was determined by SPM99 by using a threshold (p < 0.001, uncorrected) for defining the regions of interest (ROIs) in the perisylvian language region, including both the Broca area (Br) with Talairach coordinates at (−50, 12, 7) and the Wernicke area (Wn) (−57, −59, 16) and in the PMA (−18, 22, 56). For each individual, the fMRI activation index (right) was then determined by integrating the BOLD signal changes in these ROIs for statistical comparisons. Two sample t-tests were used to compare the mean of the activation index for each task. *, p < 0.05; **, p < 0.01; ns = not significant.
are different neural substrates underlying verbal and numerical processing.7,8 Second, there are differences in the brain representation of number processing between Chinese and English speakers. Although differences between the two cultures in terms of language, educational systems, or genetics may contribute to these findings, relatively greater reliance on analytic and formal logical (rather than holistic) styles of cognition among Westerners may have contributed to the greater observed activity in language-related regions among Westerners during the arithmetic task. Future cultural neuroscience research should investigate the consequences of holistic versus analytic forms of thinking on mathematical processing and would help confirm the culturally-variant patterns of neural activity observed during arithmetic tasks. Furthermore, genetics and environmental factors often work together in shaping human cognition and social behavior.9 Future studies should address how the gene × environment (or experience) interacts to affect high-level cognition in different cultures. For example, if both genes and
experience shape human cognitive functions, such as numerical processing in the brain, another challenge will be to understand how different educational systems may influence our core understanding of numbers.9
1.2 Moral Reasoning/Decision-Making—Moral Dilemmas Moral decision-making is a flourishing field of research that has attracted great scholarly attention. A growing literature has tried to uncover the neural mechanisms underlying moral decision-making with a family of moral dilemmas.10,11 Generally, a moral dilemma is a complex situation that involves a conflict in choosing between two undesirable alternatives, which would evoke the competition between deontological (nonutilitarian) choice and utilitarian response.3 For example, in a personal moral dilemma (the footbridge dilemma), the only way to save five workers from a runaway trolley is to push a large man off an overpass bridge onto the tracks below. He will die, but his body will stop the
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trolley from reaching the other five people. This is commonly referred to as the personal moral dilemma, since the participant would be personally required to engage in the harmful act. A corresponding impersonal moral dilemma is the trolley dilemma, in which the only way to save the five workers is to pull a lever redirecting the trolley onto another set of tracks, where it will kill a single worker instead of five workers.3,10,12 In this scenario, the participant does not directly and physically engage in the harmful act and is actually saving more people. These two different dilemmas usually produce distinct responses from the participants. The deontological response is an aversive emotional response to the harmful act, which would lead to the rejection of a utilitarian response. In contrast, the utilitarian response is to take part in the harmful act, since doing so will maximize good consequences, which would require overcoming the prepotent emotional response. Although the proposed actions in both personal and impersonal dilemmas would produce similar outcomes, moral judgment in the two dilemma types might be driven by different principles. Previous studies have indicated that most people show agreement with pulling the lever in the trolley dilemma and disagreement with pushing the man in the footbridge dilemma.11 Neuroimaging results revealed that personal moral dilemmas elicit greater activation in brain regions associated with emotions, whereas impersonal moral dilemmas elicit greater activation in areas associated with problem solving and working memory, suggesting that both cognitive and emotional processes contribute to moral decision-making.10,11 For both personal and impersonal ethical dilemmas, each act may lead to certain consequences, and both sides may be right in different senses. If we adopt the utilitarian way of thinking, we would conclude that it is right to kill one instead of five, but it is also right to develop an intuitive rule against the participation in killing others. However, people’s moral decisions might be influenced by cultural factors, since people’s morals and virtuousness are shaped by culture.13 Therefore, culture
should be taken into consideration when investigating moral decision-making. Research on the cultural neuroscience of moral decisionmaking suggests that members of holistic cultures (East Asians) exhibit greater integrative processing of moral dilemmas than do members of analytic cultures (Westerners). In one study (culture × type of dilemma), Wang and colleagues (2014) combined event-related potential (ERP) techniques with standardized low-resolution brain electromagnetic tomography (sLORETA) to study potential cultural variation within the brain.3 sLORETA is a method that computes images of electric activity from electroencephalogram (EEG) in a realistic head model using the MNI152 brain template and estimates the three-dimensional distribution of current density in voxels.3 In this study, Chinese and Western college students were recruited to participate in a moral dilemma task that included both personal and impersonal situations. An example of a personal situation is the footbridge dilemma, and an impersonal situation includes the trolley dilemma (see above). Each dilemma was presented in the participants’ native language (Chinese or English) and as black text against a gray background on a computer monitor, with a series of three screens. The first two screens described the scenario of a dilemma, and the third posed a question asking whether or not the hypothetical action was morally appropriate. Choosing appropriate options was considered to be utilitarian (taking part in the harmful act since doing so will maximize good consequences—saving five workers in the footbridge dilemma, which requires overcoming the prepotent emotional response), whereas choosing inappropriate options was considered to be nonutilitarian. The dependent variables were the proportion of utilitarian judgments, reaction time, ERP responses, and sLORETA activity. There was a main effect of the type of dilemma such that participants made a smaller proportion of utilitarian judgments and exhibited longer reaction times in response to personal rather than impersonal dilemmas, with no difference observed between Westerners and Chinese, as shown in Figure 3.
FIGURE 3 (A) Mean proportion of utilitarian judgments by dilemma type for Chinese and Westerners. (B) Mean reaction time by dilemma type for Chinese and Westerners. Error bars indicate standard error of the mean. V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
1. Introduction
The main focus of analysis was the P3 and P260 components (event related potential components elicited in the process of decision-making). Notably, the eventrelated potential components were significantly different between the two cultural groups. For Westerners, smaller P3 amplitudes were evoked by personal rather than impersonal dilemmas, while for Chinese participants, smaller P260 deflections were elicited by personal rather than impersonal dilemmas. The different ERP components elicited by moral dilemmas may be attributable to cultural differences. It has been widely demonstrated that East Asians and Westerners differ in experience and socialization, which influences cognition and the allocation of attention.14 Previous research has indicated that P3 is an index of inhibition of task-irrelevant emotional information, with less positive amplitudes for negative stimuli than for neutral stimuli in implicit emotional tasks.15
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The P3 results reported here are consistent with the former findings, suggesting that more negative emotions needed to be inhibited in response to personal (rather than impersonal) dilemmas. Moreover, the P260 component has been suggested to be a combination of a P2 and a P3-like process and has been reported to reflect immediate affective reactions toward options that integrate attention, working memory, and emotional processing.16 This different cognitive functioning may be related to holistic thinking. Thus, the P260 component may suggest a more integrated process during the solution of moral dilemmas in Chinese compared to Westerners. The analysis with sLORETA revealed a significantly different pattern of brain activity between Westerners and Chinese. As shown in Figure 4, the main source of both P2 and P3 components for personal dilemmas was the cingulate gyrus, similar to other studies.17 In contrast,
FIGURE 4 Grand average sLORETA images, derived from voxel-by-voxel t-test (p < 0.05). First row: grand average P2 for personal dilemmas. Second row: grand average P3 for personal dilemmas. Third row: grand average P2 for impersonal dilemmas. Fourth row: grand average P3 for impersonal dilemmas. Fifth row: grand average P260 for personal dilemmas. Sixth row: grand average P260 for impersonal dilemmas. sLORETA = standardized low-resolution brain electromagnetic tomography. Yellow–red areas indicate the activated areas (p < 0.05) and maxima are color-coded as yellow. Results are collapsed across cultures. V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
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the main sources of P2 and P3 components for impersonal dilemmas were localized in the medial frontal area and cingulate gyrus (with contributions from several other brain regions, including the temporal and insula areas). But it should be noted that EEG users have reservations concerning the accuracy of localizations using this type of software. These findings are in accordance with brain imaging research, demonstrating that a complex network of brain regions are involved in moral decision-making.18 Different from the sources of the P2 and P3 components, the P260 component for both dilemma types was mainly activated in areas in the posterior cingulate, parahippocampal gyrus, and cuneus and precuneus cortices, areas considered to be related to emotional processing and evaluation, retrieval of episodic memory representations, attention, detection of salient stimuli, and higher-order cognitive functions.19–21 It seems that brain areas associated with attention, memory retrieval, and emotional processing were involved in the process of moral decision-making and may involve holistic thinking. Future research examining cultural differences in these processes would benefit from direct manipulations of holistic and analytic thinking.
2. CONCLUDING REMARKS Although moral decision-making and cultural differences are both major themes in social psychology, the brain mechanisms underlying cross-cultural moral decision-making are still far from being well understood. In this chapter, we exemplify abstract thinking/ reasoning and moral decision-making in Eastern (e.g., Chinese) and Western (American) cultures to reveal the underlying brain mechanisms involved, using the event-related potential (ERP) technique and fMRI. These evidences suggest the extensive differences in cognitive processing and moral decision behavior between Eastern and Western cultures. Different brain patterns during the arithmetic processing and the resolution of moral dilemmas were reflected in spatiotemporal cortical activation underlying moral decision-making, and these results, using diverse methods, support a dualprocess theory of moral judgment according to which utilitarian moral judgments (favoring the “greater good” over individual rights) are enabled by controlled cognitive processes, while deontological judgments (favoring individual rights) are driven by intuitive emotional responses. Since this chapter focuses on the cross-cultural work on this topic, many studies of neural systems and various facets of moral reasoning have not been cited and discussed here (see examples22–25). Future studies will need to address the roles of cognitive control, emotion regulation, and the beliefs in these
moral reasoning and decision-making processes under diverse cultural context.
Acknowledgment This research was supported by the Office of Naval Research.
References 1. Chiao J, Cheon B, Pornpattananangkul N, Mrazek A, Blizinsky K. Cultural neuroscience: progress and promise. Psychol Inq. 2013; 24:1–19. 2. Nisbett R, Peng K, Choi I, Norenzayan A. Culture and systems of thought: holistic versus analytic cognition. Psychol Rev. 2001;108:291–310. 3. Wang Y, Deng Y, Sui D, Tang YY. Neural correlates of cultural differences in moral decision making: a combined ERP and sLORETA study. Neuroreport. 2014;25:110–116. 4. Nisbett RE. The Geography of Thought: How Asians and Westerners Think Differently and Why. New York: Free Press. 2003. 5. Tang YY, Zhang W, Chen K, et al. Arithmetic processing in the brain shaped by cultures. Proc Natl Acad Sci USA. 2006;103: 10755–10780. 6. Keller S, Crow T, Foundas A, Amunts K, Roberts N. Broca’s area: nomenclature, anatomy, typology and asymmetry. Brain and Lang. 2009;109:29–48. 7. Dehaene S, Cohen L. Towards an anatomical and functional model of number processing. Math Cogn. 1995;1:83–120. 8. Dehaene S, Spelke E, Pinel P, Stanescu R, Tsivkin S. Sources of mathematical thinking: behavioral and brainimaging evidence. Science. 1999;284:970–974. 9. Tang YY, Liu Y. Numbers in the cultural brain. Prog Brain Res. 2009;178:151–157. 10. Greene JD, Nystrom LE, Engell AD, Darley JM, Cohen JD. The neural bases of cognitive conflict and control in moral judgment. Neuron. 2004;44:389–400. 11. Greene JD. The cognitive neuroscience of moral judgment. In: Gazzaniga M, ed. The Cognitive Neurosciences IV. Cambridge: MIT Press. 2012. 12. Thomson JJ. Rights, Restitution, and Risk: Essays, in Moral Theory. Cambridge: Harvard University Press. 1986. 13. Rozin P. Five potential principles for understanding cultural differences in relation to individual differences. J Res Pers. 2003;37: 273–283. 14. Kitayama S, Park J. Cultural neuroscience of the self: understanding the social grounding of the brain. Soc Cogn Affect Neurosci. 2010;5:111–129. 15. Yuan J, Zhang Q, Chen A, et al. Are we sensitive to valence differences in emotionally negative stimuli? Electrophysiological evidence from an ERP study. Neuropsychologia. 2007;45:2764–2771. 16. Miltner W, Johnson R, Braun C, Larbig W. Somatosensory eventrelated potentials to painful and non-painful stimuli: effects of attention. Pain. 1989;38:303–312. 17. Gajewski PD, Stoerig P, Falkenstein M. ERP–correlates of response selection in a response conflict paradigm. Brain Res. 2008;1189: 127–134. 18. Prehn K, Wartenburger I, Mériau K, et al. Individual differences in moral judgment competence influence neural correlates of socionormative judgments. Soc Cogn Affect Neurosci. 2008;3:33–46. 19. Cavanna AE, Trimble MR. The precuneus: a review of its functional anatomy and behavioural correlates. Brain. 2006;129:564–583. 20. Schacter D, Addis D. The cognitive neuroscience of constructive memory: remembering the past and imagining the future. Philos Trans R Soc B: Biol Sci. 2007;362:773–786.
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References
21. Vogt BA, Vogt L, Laureys S. Cytology and functionally correlated circuits of human posterior cingulate areas. Neuroimage. 2006;29:452–466. 22. Yoder KJ, Decety J. The good, the bad, and the just: justice sensitivity predicts neural response during moral evaluation of actions performed by others. J Neurosci. 2014;34:4161–4166. 23. Zaki J, López G, Mitchell JP. Activity in ventromedial prefrontal cortex co-varies with revealed social preferences: evidence for person-invariant value. Soc Cogn Affect Neurosci. 2014;9:464–469.
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24. Young L, Camprodon JA, Hauser M, Pascual-Leone A, Saxe R. Disruption of the right temporoparietal junction with transcranial magnetic stimulation reduces the role of beliefs in moral judgments. Proc Natl Acad Sci USA. 2010;107:6753–6758. 25. Koster-Hale J, Saxe R, Dungan J, Young LL. Decoding moral judgments from neural representations of intentions. Proc Natl Acad Sci USA. 2013;110:5648–5653.
V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
14 Cultural Neuroscience of Moral Reasoning and Decision-Making Yi-Yuan Tang1, Rongxiang Tang2 1Presidential
Endowed Chair in Neuroscience, Department of Psychological Sciences, Texas Tech University, Lubbock, TX, USA; 2Department of Psychology, Washington University, St. Louis, MO, USA
O U T L I N E 1. Introduction 281 1.1 Abstract Thinking/Reasoning—Arithmetic Processing281 1.2 Moral Reasoning/Decision-Making—Moral Dilemmas283
1. INTRODUCTION Research in cultural neuroscience examines how cultural and genetic diversity shape the human mind, brain, and behavior using a variety of multimodal methods.1 Cultural differences in understanding and conceptualizing one’s relationships with others may have led to diverse cultural systems for interpreting, thinking, reasoning, and decision-making about the world. Eastern holistic systems of thought rely on connectedness and relations as a primary way of understanding the world, whereas Western analytic systems of thought rely on discreteness as an epistemological way of thinking.2 Reasoning and decision-making, as important aspects of human high-level cognition, may be influenced by cultural differences. For example, Eastern Asians tend to frame the decision to help as a matter of moral responsibility, whereas Americans are more likely to frame it as one’s personal choice.3 Previous studies indicate that from attention and cognition to social cognitive processes, neural systems have likewise adapted differently across cultural contexts to facilitate divergent systems of social interactions and
Neuroimaging Personality, Social Cognition, and Character http://dx.doi.org/10.1016/B978-0-12-800935-2.00014-2
2. Concluding Remarks
286
Acknowledgment286 References286
relations.4 In this chapter, we will focus on the cultural differences in high-level cognition (moral reasoning and decision-making), especially between the Chinese and American cultures. We will explore the associated brain networks of cultural variation involved in these processes and will take abstract thinking/reasoning and moral decision-making as examples to demonstrate the neural basis of cultural influences on these processes that involve Eastern and Western cultures. This focus reflects the current growing theoretical and experimental curiosity among behavioral scientists and neuroscientists, as well as the general public.5 We acknowledge that this chapter provides an incomplete view of the literature on moral reasoning and decision-making.
1.1 Abstract Thinking/Reasoning—Arithmetic Processing Arithmetic or math processing often involves abstract thinking/reasoning. One example of a higher cognitive function that may be influenced by holistic vs. analytic thinking styles involves discrete neural patterns of arithmetic processing
281
Copyright © 2016 Elsevier Inc. All rights reserved.
282
14. MORAL REASONING AND DECISION-MAKING
in Chinese and Westerners.5 The universal use of Arabic numbers in mathematics raises the question of whether they are processed the same way in people from different cultures who speak different languages, such as Chinese and English. To address this question, researchers used functional Magnetic Resonance Imaging (fMRI) to scan 12 native Chinese speakers (NCS) and 12 native English speakers (NES) who possessed a college-level education. The participants were instructed to perform four tasks during the scanning (see Figure 1 for examples): (1) the symbol condition: judge the spatial orientation of nonnumerical stimuli in which a triplet of nonsemantic characters or symbols are visually presented either in an upright or in an italic orientation. The task was to decide whether the third symbol had the same orientation as the first two; (2) the number condition: judge the spatial orientation of numerical stimuli, using the same task as in the symbol condition except for using Arabic digits as visual stimuli; (3) the addition condition: determine whether the third digit was equal to the sum of the first two in a triplet of Arabic numbers; and (4) the comparison condition: determine whether the third digit was larger than the larger of the first two in a triplet of Arabic numbers. A baseline condition of matching white and/ or gray circular dots was used to control for the motor and nonspecific visual components of the tasks. Results indicated a different cortical representation of numbers between native Chinese speakers and native English speakers. While the English speakers employed a language process relying on the left perisylvian cortices for mental calculation, such as a simple addition task, the Chinese speakers instead engaged a visuo–premotor association network for the same task (see Figure 1). We further chose two regions of interest, the perisylvian area, including both the Broca (Br) and Wernicke (Wn) areas, and the premotor association area between BA6, BA8, and BA9.6 Quantitative analyses were conducted by comparing the fMRI signal between the English and Chinese groups. We found the perisylvian activations were significantly larger in the English speakers than in the Chinese speakers (Figure 2(A)). As the arithmetic complexity increased across the four conditions (Symbol < Number < Addition < Comparison), there was a trend toward increased premotor activation in the Chinese speakers, but not in the English speakers (Figure 2(B)). Therefore, there was a double dissociation in brain activation between these two groups during these tasks, supporting clear cultural differences in the processing of numbers. In addition, for both cultural groups, the inferior parietal cortex was activated in the numerical quantity comparison. However, the fMRI connectivity analyses6 revealed a difference in the brain networks involved in the task for Chinese and English speakers. Two distinct patterns were observed in the functional networks: there was dorsal visuo-pathway dominance
(A)
(B)
(C)
(D)
FIGURE 1 Dissociation in the brain representation of Arabic numbers between native Chinese speakers (NCS) and native English speakers (NES). (A) During the symbol task in NCS. (B) During the number task in NCS. (C) During the symbol task in NES. (D) During the number task in NES. The task-dependent brain activation was determined by Statistical Parametric Mapping (SPM) by using a liberal threshold (p < 0.05) for illustrating a global pattern of the fMRI blood-oxygen-level dependent (BOLD) signal changes. The type-I error of detecting the difference was corrected for the number of resolution elements at each of the activated brain regions defined anatomically by using the SPM add-on toolbox automated anatomical labeling (AAL). The multiple comparison correction is the small volume correction (SVC) procedure implemented in SPM. (A and B) Examples of the visual stimuli used for the symbol task and the number task, respectively, are shown at the top. LH = left hemisphere; RH = right hemisphere; Br = Broca area; Wn = Wernicke area.
(through the parietal–occipital cortex) for the Chinese speakers, but ventral visuo-pathway dominance (through the temporal cortex) for the English speakers. Our findings have two implications. First, in both Chinese and English speakers, there is cortical dissociation between addition and numerical comparison processing. The addition task seems to be more dependent upon language processing than does the comparison task, which is consistent with the notion that there
V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
1. Introduction
283
FIGURE 2 Comparison of the activation intensity between native Chinese speakers (NCS) and native English speakers (NES) in the perisylvian language region (A) and the premotor association area (PMA) (B). The brain activation maps (left) were determined by contrasting BOLD signals between NCS and NES only during the comparison task, with the NES group showing relative increase of the signal (A, English > Chinese), and the NCS group showing relative increase of the signal (B, Chinese > English). The within-group task-dependent activation was determined by SPM99 by using a threshold (p < 0.001, uncorrected) for defining the regions of interest (ROIs) in the perisylvian language region, including both the Broca area (Br) with Talairach coordinates at (−50, 12, 7) and the Wernicke area (Wn) (−57, −59, 16) and in the PMA (−18, 22, 56). For each individual, the fMRI activation index (right) was then determined by integrating the BOLD signal changes in these ROIs for statistical comparisons. Two sample t-tests were used to compare the mean of the activation index for each task. *, p < 0.05; **, p < 0.01; ns = not significant.
are different neural substrates underlying verbal and numerical processing.7,8 Second, there are differences in the brain representation of number processing between Chinese and English speakers. Although differences between the two cultures in terms of language, educational systems, or genetics may contribute to these findings, relatively greater reliance on analytic and formal logical (rather than holistic) styles of cognition among Westerners may have contributed to the greater observed activity in language-related regions among Westerners during the arithmetic task. Future cultural neuroscience research should investigate the consequences of holistic versus analytic forms of thinking on mathematical processing and would help confirm the culturally-variant patterns of neural activity observed during arithmetic tasks. Furthermore, genetics and environmental factors often work together in shaping human cognition and social behavior.9 Future studies should address how the gene × environment (or experience) interacts to affect high-level cognition in different cultures. For example, if both genes and
experience shape human cognitive functions, such as numerical processing in the brain, another challenge will be to understand how different educational systems may influence our core understanding of numbers.9
1.2 Moral Reasoning/Decision-Making—Moral Dilemmas Moral decision-making is a flourishing field of research that has attracted great scholarly attention. A growing literature has tried to uncover the neural mechanisms underlying moral decision-making with a family of moral dilemmas.10,11 Generally, a moral dilemma is a complex situation that involves a conflict in choosing between two undesirable alternatives, which would evoke the competition between deontological (nonutilitarian) choice and utilitarian response.3 For example, in a personal moral dilemma (the footbridge dilemma), the only way to save five workers from a runaway trolley is to push a large man off an overpass bridge onto the tracks below. He will die, but his body will stop the
V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
284
14. MORAL REASONING AND DECISION-MAKING
trolley from reaching the other five people. This is commonly referred to as the personal moral dilemma, since the participant would be personally required to engage in the harmful act. A corresponding impersonal moral dilemma is the trolley dilemma, in which the only way to save the five workers is to pull a lever redirecting the trolley onto another set of tracks, where it will kill a single worker instead of five workers.3,10,12 In this scenario, the participant does not directly and physically engage in the harmful act and is actually saving more people. These two different dilemmas usually produce distinct responses from the participants. The deontological response is an aversive emotional response to the harmful act, which would lead to the rejection of a utilitarian response. In contrast, the utilitarian response is to take part in the harmful act, since doing so will maximize good consequences, which would require overcoming the prepotent emotional response. Although the proposed actions in both personal and impersonal dilemmas would produce similar outcomes, moral judgment in the two dilemma types might be driven by different principles. Previous studies have indicated that most people show agreement with pulling the lever in the trolley dilemma and disagreement with pushing the man in the footbridge dilemma.11 Neuroimaging results revealed that personal moral dilemmas elicit greater activation in brain regions associated with emotions, whereas impersonal moral dilemmas elicit greater activation in areas associated with problem solving and working memory, suggesting that both cognitive and emotional processes contribute to moral decision-making.10,11 For both personal and impersonal ethical dilemmas, each act may lead to certain consequences, and both sides may be right in different senses. If we adopt the utilitarian way of thinking, we would conclude that it is right to kill one instead of five, but it is also right to develop an intuitive rule against the participation in killing others. However, people’s moral decisions might be influenced by cultural factors, since people’s morals and virtuousness are shaped by culture.13 Therefore, culture
should be taken into consideration when investigating moral decision-making. Research on the cultural neuroscience of moral decisionmaking suggests that members of holistic cultures (East Asians) exhibit greater integrative processing of moral dilemmas than do members of analytic cultures (Westerners). In one study (culture × type of dilemma), Wang and colleagues (2014) combined event-related potential (ERP) techniques with standardized low-resolution brain electromagnetic tomography (sLORETA) to study potential cultural variation within the brain.3 sLORETA is a method that computes images of electric activity from electroencephalogram (EEG) in a realistic head model using the MNI152 brain template and estimates the three-dimensional distribution of current density in voxels.3 In this study, Chinese and Western college students were recruited to participate in a moral dilemma task that included both personal and impersonal situations. An example of a personal situation is the footbridge dilemma, and an impersonal situation includes the trolley dilemma (see above). Each dilemma was presented in the participants’ native language (Chinese or English) and as black text against a gray background on a computer monitor, with a series of three screens. The first two screens described the scenario of a dilemma, and the third posed a question asking whether or not the hypothetical action was morally appropriate. Choosing appropriate options was considered to be utilitarian (taking part in the harmful act since doing so will maximize good consequences—saving five workers in the footbridge dilemma, which requires overcoming the prepotent emotional response), whereas choosing inappropriate options was considered to be nonutilitarian. The dependent variables were the proportion of utilitarian judgments, reaction time, ERP responses, and sLORETA activity. There was a main effect of the type of dilemma such that participants made a smaller proportion of utilitarian judgments and exhibited longer reaction times in response to personal rather than impersonal dilemmas, with no difference observed between Westerners and Chinese, as shown in Figure 3.
FIGURE 3 (A) Mean proportion of utilitarian judgments by dilemma type for Chinese and Westerners. (B) Mean reaction time by dilemma type for Chinese and Westerners. Error bars indicate standard error of the mean. V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
1. Introduction
The main focus of analysis was the P3 and P260 components (event related potential components elicited in the process of decision-making). Notably, the eventrelated potential components were significantly different between the two cultural groups. For Westerners, smaller P3 amplitudes were evoked by personal rather than impersonal dilemmas, while for Chinese participants, smaller P260 deflections were elicited by personal rather than impersonal dilemmas. The different ERP components elicited by moral dilemmas may be attributable to cultural differences. It has been widely demonstrated that East Asians and Westerners differ in experience and socialization, which influences cognition and the allocation of attention.14 Previous research has indicated that P3 is an index of inhibition of task-irrelevant emotional information, with less positive amplitudes for negative stimuli than for neutral stimuli in implicit emotional tasks.15
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The P3 results reported here are consistent with the former findings, suggesting that more negative emotions needed to be inhibited in response to personal (rather than impersonal) dilemmas. Moreover, the P260 component has been suggested to be a combination of a P2 and a P3-like process and has been reported to reflect immediate affective reactions toward options that integrate attention, working memory, and emotional processing.16 This different cognitive functioning may be related to holistic thinking. Thus, the P260 component may suggest a more integrated process during the solution of moral dilemmas in Chinese compared to Westerners. The analysis with sLORETA revealed a significantly different pattern of brain activity between Westerners and Chinese. As shown in Figure 4, the main source of both P2 and P3 components for personal dilemmas was the cingulate gyrus, similar to other studies.17 In contrast,
FIGURE 4 Grand average sLORETA images, derived from voxel-by-voxel t-test (p < 0.05). First row: grand average P2 for personal dilemmas. Second row: grand average P3 for personal dilemmas. Third row: grand average P2 for impersonal dilemmas. Fourth row: grand average P3 for impersonal dilemmas. Fifth row: grand average P260 for personal dilemmas. Sixth row: grand average P260 for impersonal dilemmas. sLORETA = standardized low-resolution brain electromagnetic tomography. Yellow–red areas indicate the activated areas (p < 0.05) and maxima are color-coded as yellow. Results are collapsed across cultures. V. BRAIN IMAGING PERSPECTIVES ON THE BASIS OF PROSOCIABILITY
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the main sources of P2 and P3 components for impersonal dilemmas were localized in the medial frontal area and cingulate gyrus (with contributions from several other brain regions, including the temporal and insula areas). But it should be noted that EEG users have reservations concerning the accuracy of localizations using this type of software. These findings are in accordance with brain imaging research, demonstrating that a complex network of brain regions are involved in moral decision-making.18 Different from the sources of the P2 and P3 components, the P260 component for both dilemma types was mainly activated in areas in the posterior cingulate, parahippocampal gyrus, and cuneus and precuneus cortices, areas considered to be related to emotional processing and evaluation, retrieval of episodic memory representations, attention, detection of salient stimuli, and higher-order cognitive functions.19–21 It seems that brain areas associated with attention, memory retrieval, and emotional processing were involved in the process of moral decision-making and may involve holistic thinking. Future research examining cultural differences in these processes would benefit from direct manipulations of holistic and analytic thinking.
2. CONCLUDING REMARKS Although moral decision-making and cultural differences are both major themes in social psychology, the brain mechanisms underlying cross-cultural moral decision-making are still far from being well understood. In this chapter, we exemplify abstract thinking/ reasoning and moral decision-making in Eastern (e.g., Chinese) and Western (American) cultures to reveal the underlying brain mechanisms involved, using the event-related potential (ERP) technique and fMRI. These evidences suggest the extensive differences in cognitive processing and moral decision behavior between Eastern and Western cultures. Different brain patterns during the arithmetic processing and the resolution of moral dilemmas were reflected in spatiotemporal cortical activation underlying moral decision-making, and these results, using diverse methods, support a dualprocess theory of moral judgment according to which utilitarian moral judgments (favoring the “greater good” over individual rights) are enabled by controlled cognitive processes, while deontological judgments (favoring individual rights) are driven by intuitive emotional responses. Since this chapter focuses on the cross-cultural work on this topic, many studies of neural systems and various facets of moral reasoning have not been cited and discussed here (see examples22–25). Future studies will need to address the roles of cognitive control, emotion regulation, and the beliefs in these
moral reasoning and decision-making processes under diverse cultural context.
Acknowledgment This research was supported by the Office of Naval Research.
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