Neuroethics

, Volume 4, Issue 2, pp 143–162 | Cite as

The Dual Track Theory of Moral Decision-Making: a Critique of the Neuroimaging Evidence

Original Paper

Abstract

The dual-track theory of moral reasoning has received considerable attention due to the neuroimaging work of Greene et al. Greene et al. claimed that certain kinds of moral dilemmas activated brain regions specific to emotional responses, while others activated areas specific to cognition. This appears to indicate a dissociation between different types of moral reasoning. I re-evaluate these claims of specificity in light of subsequent empirical work. I argue that none of the cortical areas identified by Greene et al. are functionally specific: each is active in a wide variety of both cognitive and emotional tasks. I further argue that distinct activation across conditions is not strong evidence for dissociation. This undermines support for the dual-track hypothesis. I further argue that moral decision-making appears to activate a common network that underlies self-projection: the ability to imagine oneself from a variety of viewpoints in a variety of situations. I argue that the utilization of self-projection indicates a continuity between moral decision-making and other kinds of complex social deliberation. This may have normative consequences, but teasing them out will require careful attention to both empirical and philosophical concerns.

Keywords

Morality Neuroimaging Reverse inference Self-projection 

References

  1. 1.
    Adam Smith. 1982. The theory of moral sentiments. Indianapolis: Liberty Fund.Google Scholar
  2. 2.
    Greene, Joshua D., Leigh E. Nystrom, Andrew D. Engell, John M. Darley, and Jonathan D Cohen. 2004. The neural bases of cognitive conflict and control in moral judgment. Neuron 44(2):389–400.Google Scholar
  3. 3.
    Berker, Selim. 2009. The normative insignificance of neuroscience. Philosophy & Public Affairs 37(4):293–329.CrossRefGoogle Scholar
  4. 4.
    Greene, J.D., R.B. Sommerville, L.E. Nystrom, J.M. Darley, and J.D. Cohen. 2001. An fMRI investigation of emotional engagement in moral judgment. Science 293(5537): 2105–2108.CrossRefGoogle Scholar
  5. 5.
    Greene, Joshua D. 2008. The secret joke of Kant’s soul. In Moral psychology, ed. Walter Sinnott-Armstrong, vol. 3, 35–80. Cambridge: MIT Press.Google Scholar
  6. 6.
    Singer, P. 2005. Ethics and intuitions. The Journal of Ethics 9(3): 331–352.CrossRefGoogle Scholar
  7. 7.
    Allman, J., and J. Woodward. 2008. What are moral intuitions and why should we care about them: A neurobiological perspective. Philosophical Issues 18(1): 164–185.CrossRefGoogle Scholar
  8. 8.
    Kamm, F.M. 2009. Neuroscience and moral reasoning: A note on recent research. Philosophy & Public Affairs 37(4): 330–345.CrossRefGoogle Scholar
  9. 9.
    Henson, Richard. 2005. What can functional neuroimaging tell the experimental psychologist? The Quarterly Journal of Experimental Psychology 58(2): 193–233.Google Scholar
  10. 10.
    Poldrack, Russell A. 2008. The role of fMRI in cognitive neuroscience: where do we stand? Current Opinion in Neurobiology 18(2): 223–227.CrossRefGoogle Scholar
  11. 11.
    Price, C.J., and K.J. Friston. 2005. Functional ontologies for cognition: The systematic definition of structure and function. Cognitive Neuropsychology 22(3): 262–275.CrossRefGoogle Scholar
  12. 12.
    Poldrack, Russell A. 2006. Can cognitive processes be inferred from neuroimaging data? Trends in Cognitive Sciences 10(2): 59–63.CrossRefGoogle Scholar
  13. 13.
    Maddock, R.J. 1999. The retrosplenial cortex and emotion: New insights from functional neuroimaging of the human brain. Trends in Neurosciences 22(7): 310–316.CrossRefGoogle Scholar
  14. 14.
    Kober, Hedy, Lisa Feldman Barrett, Josh Joseph, Eliza Bliss-Moreau, Kristen Lindquist, and Tor D. Wager. 2008. Functional grouping and cortical-subcortical interactions in emotion: A meta-analysis of neuroimaging studies. Neuroimage 42(2): 998–1031.Google Scholar
  15. 15.
    Cavanna, A.E., and M.R. Trimble. 2006. The precuneus: A review of its functional anatomy and behavioural correlates. Brain 129(3): 564.CrossRefGoogle Scholar
  16. 16.
    Vogt, B.A., and S. Laureys. 2005. Posterior cingulate, precuneal & retrosplenial cortices: Cytology & components of the neural network correlates of consciousness. Progress in Brain Research 150: 205.CrossRefGoogle Scholar
  17. 17.
    Vogeley, K., and G.R. Fink. 2003. Neural correlates of the first-person-perspective. Trends in Cognitive Sciences 7(1): 38–42.CrossRefGoogle Scholar
  18. 18.
    Vogeley, K., M. May, A. Ritzl, P. Falkai, K. Zilles, and G.R. Fink. 2004. Neural correlates of first-person perspective as one constituent of human self-consciousness. Journal of Cognitive Neuroscience 16(5): 817–827.CrossRefGoogle Scholar
  19. 19.
    Jackson, P.L., E. Brunet, A.N. Meltzoff, and J. Decety. 2006. Empathy examined through the neural mechanisms involved in imagining how I feel versus how you feel pain. Neuropsychologia 44(5): 752–761.CrossRefGoogle Scholar
  20. 20.
    Saxe, R., and N. Kanwisher. 2003. People thinking about thinking people the role of the temporo-parietal junction in “theory of mind”. Neuroimage 19(4): 1835–1842.CrossRefGoogle Scholar
  21. 21.
    Ochsner, K.N., K. Knierim, D.H. Ludlow, J. Hanelin, T. Ramachandran, G. Glover, and S.C. Mackey. 2004. Reflecting upon feelings: An fMRI study of neural systems supporting the attribution of emotion to self and other. Journal of Cognitive Neuroscience 16(10): 1746–1772.CrossRefGoogle Scholar
  22. 22.
    Okuda, J., T. Fujii, H. Ohtake, T. Tsukiura, K. Tanji, K. Suzuki, R. Kawashima, H. Fukuda, M. Itoh, and A. Yamadori. 2003. Thinking of the future and past: The roles of the frontal pole and the medial temporal lobes. Neuroimage 19(4): 1369–1380.CrossRefGoogle Scholar
  23. 23.
    Addis, D.R., A.T. Wong, and D.L. Schacter. 2007. Remembering the past and imagining the future: Common and distinct neural substrates during event construction and elaboration. Neuropsychologia 45(7): 1363–1377.CrossRefGoogle Scholar
  24. 24.
    Johnson, M.K., C.L. Raye, K.J. Mitchell, S.R. Touryan, E.J. Greene, and S. Nolen-Hoeksema. 2006. Dissociating medial frontal and posterior cingulate activity during self-reflection. Social Cognitive and Affective Neuroscience 1(1): 56.CrossRefGoogle Scholar
  25. 25.
    Ochsner, K.N., J.S. Beer, E.R. Robertson, J.C. Cooper, J.D.E. Gabrieli, J.F. Kihsltrom, and M. D’Esposito. 2005. The neural correlates of direct and reflected self-knowledge. Neuroimage 28(4): 797–814.CrossRefGoogle Scholar
  26. 26.
    Fransson, P. and G. Marrelec. 2008. The precuneus/posterior cingulate cortex plays a pivotal role in the default mode network: Evidence from a partial correlation network analysis. Neuroimage 42(3): 1178–1184.Google Scholar
  27. 27.
    Gusnard, D.A., E. Akbudak, G.L. Shulman, and M.E. Raichle. 2001. Medial prefrontal cortex and self-referential mental activity: Relation to a default mode of brain function. Proceedings of the National Academy of Sciences 98(7): 4259–4264.Google Scholar
  28. 28.
    Vann, Seralynne D., John P. Aggleton, and Eleanor A. Maguire. 2009. What does the retrosplenial cortex do? Nature Reviews Neuroscience 10: 792–802.CrossRefGoogle Scholar
  29. 29.
    Borg, J.S., C. Hynes, J. Van Horn, S. Grafton, and W. Sinnott-Armstrong. 2006. Consequences, action, and intention as factors in moral judgments: An fMRI investigation. Journal of Cognitive Neuroscience 18(5): 803–817.CrossRefGoogle Scholar
  30. 30.
    Hein, G., and R.T. Knight. 2008. Superior temporal sulcus—It’s my area: Or is it? Journal of Cognitive Neuroscience 20(12): 2125–2136.CrossRefGoogle Scholar
  31. 31.
    Engell, A.D., and J.V. Haxby. 2007. Facial expression and gaze-direction in human superior temporal sulcus. Neuropsychologia 45(14): 3234–3241.CrossRefGoogle Scholar
  32. 32.
    Materna, S., P.W. Dicke, and P. Thier. 2008. The posterior superior temporal sulcus is involved in social communication not specific for the eyes. Neuropsychologia 46(11): 2759–2765.CrossRefGoogle Scholar
  33. 33.
    Redcay, E. 2008. The superior temporal sulcus performs a common function for social and speech perception: Implications for the emergence of autism. Neuroscience and Biobehavioral Reviews 32(1): 123–142.CrossRefGoogle Scholar
  34. 34.
    Kosslyn, S.M., L.M. Shin, W.L. Thompson, R.J. McNally, S.L. Rauch, R.K. Pitman, and N.M. Alpert. 1996. Neural effects of visualizing and perceiving aversive stimuli: A PET investigation. Neuroreport 7(10): 1569.CrossRefGoogle Scholar
  35. 35.
    Reiman, E.M., R.D. Lane, G.L. Ahern, G.E. Schwartz, R.J. Davidson, K.J. Friston, L.S. Yun, and K. Chen. 1997. Neuroanatomical correlates of externally and internally generated human emotion. American Journal of Psychiatry 154(7): 918–925.Google Scholar
  36. 36.
    Wager, T.D., and E.E. Smith. 2003. Neuroimaging studies of working memory: A meta-analysis. Cogn Affect Behav Neurosci 3(4): 255–274.CrossRefGoogle Scholar
  37. 37.
    Borg, J.S., D. Lieberman, and K.A. Kiehl. 2008. Infection, incest, and iniquity: Investigating the neural correlates of disgust and morality. Journal of Cognitive Neuroscience 20(9): 1529–1546.CrossRefGoogle Scholar
  38. 38.
    Haidt, J. 2001. The emotional dog and its rational tail. Psychological Review 108(4): 814–834.CrossRefGoogle Scholar
  39. 39.
    Saxe, R., and A. Wexler. 2005. Making sense of another mind: The role of the right temporo-parietal junction. Neuropsychologia 43(10): 1391–1399.CrossRefGoogle Scholar
  40. 40.
    Samson, D., I.A. Apperly, C. Chiavarino, and G.W. Humphreys. 2004. Left temporoparietal junction is necessary for representing someone else’s belief. Nature Neuroscience 7(5): 499–500.CrossRefGoogle Scholar
  41. 41.
    Young, L., and R. Saxe. 2008. The neural basis of belief encoding and integration in moral judgment. Neuroimage 40(4): 1912–1920.CrossRefGoogle Scholar
  42. 42.
    Young, L., and R. Saxe. 2009. An fMRI investigation of spontaneous mental state inference for moral judgment. Journal of Cognitive Neuroscience 21(7): 1396–1405.CrossRefGoogle Scholar
  43. 43.
    Bechara, A., and A.R. Damasio. 2005. The somatic marker hypothesis: A neural theory of economic decision. Games and Economic Behavior 52(2): 336–372.CrossRefGoogle Scholar
  44. 44.
    Greene, J.D. 2007. Why are VMPFC patients more utilitarian? A dual-process theory of moral judgment explains. Trends in Cognitive Sciences 11(8): 322–323.CrossRefGoogle Scholar
  45. 45.
    Kahane, Guy, and Nicholas Shackel. 2008. Do abnormal responses show utilitarian bias? Nature 452(7185): E5.CrossRefGoogle Scholar
  46. 46.
    Koenigs, Michael, and Daniel Tranel. 2007. Irrational economic decision-making after ventromedial prefrontal damage: Evidence from the ultimatum game. Journal of Neuroscience 27(4): 951–956.CrossRefGoogle Scholar
  47. 47.
    Koenigs, Michael, Liane Young, Ralph Adolphs, Daniel Tranel, Fiery Cushman, Marc Hauser, and Antonio Damasio. 2007. Damage to the prefrontal cortex increases utilitarian moral judgements. Nature 446(7138): 908–911.CrossRefGoogle Scholar
  48. 48.
    Moll, J., and R. de Oliveira-Souza. 2007. Response to Greene: Moral sentiments and reason: Friends or foes? Trends in Cognitive Sciences 11(8): 323–324.CrossRefGoogle Scholar
  49. 49.
    Damasio, A.R. 1994. Descartes’ error: Emotion, reason, and the human brain. New York: GP Putnam’s Sons.Google Scholar
  50. 50.
    Badre, David, and Mark D’Esposito. 2009. Is the rostro-caudal axis of the frontal lobe hierarchical? Nature Reviews Neuroscience 10(9): 659–669.CrossRefGoogle Scholar
  51. 51.
    Nachev, Christopher Kennard Parashkev, and Masud Husain. 2009. The functional anatomy of the frontal lobes. Nature Reviews Neuroscience 10(11): 829.CrossRefGoogle Scholar
  52. 52.
    Amodio, D.M., and C.D. Frith. 2006. Meeting of minds: The medial frontal cortex and social cognition. Nature Reviews Neuroscience 7(4): 268–277.CrossRefGoogle Scholar
  53. 53.
    Hare, Todd A., Colin F. Camerer, and Antonio Rangel. 2009. Self-control in decision-making involves modulation of the vmPFC valuation system. Science 324(5927): 646–648.Google Scholar
  54. 54.
    Kable, J.W., and P.W. Glimcher. 2007. The neural correlates of subjective value during intertemporal choice. Nature Neuroscience 10(12): 1625–1633.CrossRefGoogle Scholar
  55. 55.
    Heekeren, H.R., I. Wartenburger, H. Schmidt, K. Prehn, H.P. Schwintowski, and A. Villringer. 2005. Influence of bodily harm on neural correlates of semantic and moral decision-making. Neuroimage 24(3): 887–897.CrossRefGoogle Scholar
  56. 56.
    Prehn, K., I. Wartenburger, K. Meriau, C. Scheibe, O.R. Goodenough, A. Villringer, E. van der Meer, and H.R. Heekeren. 2008. Individual differences in moral judgment competence influence neural correlates of socio-normative judgments. Social Cognitive and Affective Neuroscience 3(1): 33.Google Scholar
  57. 57.
    Moll, J., R. de Oliveira-Souza, P.J. Eslinger, I.E. Bramati, J. Mourao-Miranda, P.A. Andreiuolo, and L. Pessoa. 2002. The neural correlates of moral sensitivity: A functional magnetic resonance imaging investigation of basic and moral emotions. Journal of Neuroscience 22(7): 2730.Google Scholar
  58. 58.
    Moll, J., R. de Oliveira-Souza, G.J. Garrido, I.E. Bramati, E.M.A. Caparelli-Daquer, M.L.M.F. Paiva, R. Zahn, and J. Grafman. 2007. The self as a moral agent: Linking the neural bases of social agency and moral sensitivity. Social Neuroscience 2(3): 336–352.CrossRefGoogle Scholar
  59. 59.
    Mitchell, J.P., M.R. Banaji, and C.N. MacRae. 2005. The link between social cognition and self-referential thought in the medial prefrontal cortex. Journal of Cognitive Neuroscience 17(8): 1306–1315.CrossRefGoogle Scholar
  60. 60.
    Robertson, D., J. Snarey, O. Ousley, K. Harenski, F.D.B. Bowman, R. Gilkey, and C. Kilts. 2007. The neural processing of moral sensitivity to issues of justice and care. Neuropsychologia 45(4): 755–766.CrossRefGoogle Scholar
  61. 61.
    Finger, E.C., A.A. Marsh, N. Kamel, D.G.V. Mitchell, and J.R. Blair. 2006. Caught in the act: The impact of audience on the neural response to morally and socially inappropriate behavior. NeuroImage 33(1): 414–421.CrossRefGoogle Scholar
  62. 62.
    Kiehl, Kent A. 2008. Without morals: The cognitive neuroscience of criminal psychopaths. In Moral psychology, ed. Walter Sinnott-Armstrong, vol. 3, 119–150. Cambridge: MIT Press.Google Scholar
  63. 63.
    de Oliveira-Souza, Ricardo, Fátima Azavedo Ignácio, and Jorge Moll. 2008. The antisocials among us. In Moral psychology, ed. Walter Sinnott-Armstrong, vol. 3, 151–158. Cambridge: MIT Press.Google Scholar
  64. 64.
    Compton, R.J., M.T. Banich, A. Mohanty, M.P. Milham, J. Herrington, G.A. Miller, P.E. Scalf, A. Webb, and W. Heller. 2003. Paying attention to emotion: An fmri investigation of cognitive and emotional stroop tasks. Cognitive, Affective & Behavioral Neuroscience 3(2): 81–96.CrossRefGoogle Scholar
  65. 65.
    Etkin, A., T. Egner, D.M. Peraza, E.R. Kandel, and J. Hirsch. 2006. Resolving emotional conflict: A role for the rostral anterior cingulate cortex in modulating activity in the amygdala. Neuron 51(6): 871–882.CrossRefGoogle Scholar
  66. 66.
    Boettiger, C.A., and M. D’Esposito. 2005. Frontal networks for learning and executing arbitrary stimulus-response associations. Journal of Neuroscience 25(10): 2723.CrossRefGoogle Scholar
  67. 67.
    Bunge, Silvia A. 2004. How we use rules to select actions: A review of evidence from cognitive neuroscience. Cognitive, Affective, & Behavioral Neuroscience 4(4): 564–579.CrossRefGoogle Scholar
  68. 68.
    Pessoa, Luiz. 2008. On the relationship between emotion and cognition. Nature Reviews Neuroscience 9(2): 148–158.CrossRefGoogle Scholar
  69. 69.
    Greene, J.D., S.A. Morelli, K. Lowenberg, L.E. Nystrom, and J.D. Cohen. 2008. Cognitive load selectively interferes with utilitarian moral judgment. Cognition 107(3): 1144–1154.CrossRefGoogle Scholar
  70. 70.
    Mole, Chris, and Colin Klein. 2010. Confirmation, refutation and the evidence in fMRI. In Foundational issues in human brain mapping, ed. Stephen José Hanson, and Martin Bunzl. 99–112. Cambridge: MIT Press.Google Scholar
  71. 71.
    Craig, A.D. 2002. How do you feel? Interoception: The sense of the physiological condition of the body. Nature Reviews Neuroscience 3: 655–666.Google Scholar
  72. 72.
    Craig, A.D. 2008. Interoception and emotion: A neuroanatomical perspective. In Handbook of emotion. ed. Michael Lewis, Jeannette M. Haviland-Jones, and Lisa Feldman Barrett. 272–288. New York: The Guilford Press.Google Scholar
  73. 73.
    Sanfey, Alan G., James K. Rilling, Jessica A. Aronson, Leigh E. Nystrom, and Jonathan D. Cohen. 2003. The neural basis of economic decision-making in the ultimatum game. Science 300(5626): 1755–1758.CrossRefGoogle Scholar
  74. 74.
    Kravitz, D.A., and S. Gunto. 1992. Decisions and perceptions of recipients in ultimatum bargaining games. Journal of Socio-Economics 21(1): 65–84.CrossRefGoogle Scholar
  75. 75.
    Yamagishi, Toshio, Yutaka Horita, Haruto Takagishi, Mizuho Shinada, Shigehito Tanida, and Karen S. Cook. 2009. The private rejection of unfair offers and emotional commitment. Proceedings of the National Academy of Sciences 106(28): 11520–11523.CrossRefGoogle Scholar
  76. 76.
    Grahek, Nicola. 2007. Feeling pain and being in pain. Cambridge, MA: The MIT Press.Google Scholar
  77. 77.
    Barrett, L.F., and E. Bliss-Moreau. 2009. Affect as a psychological primitive. Advances in Experimental Social Psychology 41: 167–218.CrossRefGoogle Scholar
  78. 78.
    Quartz, S.R. 2009. Reason, emotion and decision-making: Risk and reward computation with feeling. Trends in Cognitive Sciences 13(5): 209–215.CrossRefGoogle Scholar
  79. 79.
    Duncan, S., and L.F. Barrett. 2007. Affect is a form of cognition: A neurobiological analysis. Cognition & Emotion 21(6): 1184.CrossRefGoogle Scholar
  80. 80.
    Camerer, C., G. Loewenstein, and D. Prelec. 2005. Neuroeconomics: How neuroscience can inform economics. Journal of Economic Literature 43(1): 9–64.CrossRefGoogle Scholar
  81. 81.
    Mole, C., C. Kubatzky, J. Plate, R. Waller, M. Dobbs, and M. Nardone. 2007. Faces and brains: The limitations of brain scanning in cognitive science. Philosophical Psychology 20(2): 197–207.CrossRefGoogle Scholar
  82. 82.
    Moll, Jorge, and Ricardo de Oliveira-Souza. 2007. Moral judgments, emotions and the utilitarian brain. Trends in Cognitive Sciences 11(8): 319–321.CrossRefGoogle Scholar
  83. 83.
    Moll, J., R. Zahn, R. de Oliveira-Souza, F. Krueger, and J. Grafman. 2005. The neural basis of human moral cognition. Nature Reviews Neuroscience 6(10): 799–809.CrossRefGoogle Scholar
  84. 84.
    Coltheart, Max. 2006. What has functional neuroimaging told us about the mind (so far)? Cortex 42(3): 323–331.CrossRefGoogle Scholar
  85. 85.
    Indefrey, P. 2006. A meta-analysis of hemodynamic studies on first and second language processing: Which suggested differences can we trust and what do they mean? Language Learning 56: 279–304.CrossRefGoogle Scholar
  86. 86.
    Meehl, Paul E. 1978. Theoretical risks and tabular asterisks: Sir Karl, Sir Ronald, and the slow progress of soft psychology. Journal of Consulting and Clinical Psychology 46: 806–834.CrossRefGoogle Scholar
  87. 87.
    Klein, Colin. 2010. Images are not the evidence of neuroimaging. British Journal for the Philosophy of Science 61: 265–278.CrossRefGoogle Scholar
  88. 88.
    Savoy, Robert L. 2001. History and future directions of human brain mapping and functional imaging. Acta Psychologica 107: 9–42.CrossRefGoogle Scholar
  89. 89.
    Anderson, M.L. 2007. The massive redeployment hypothesis and the functional topography of the brain. Philosophical Psychology 20(2): 143–174.CrossRefGoogle Scholar
  90. 90.
    Buckner, R.L., and D.C. Carroll. 2007. Self-projection and the brain. Trends in Cognitive Sciences 11(2): 49–57.CrossRefGoogle Scholar
  91. 91.
    Schacter, D.L., D.R. Addis, and R.L. Buckner. 2007. Remembering the past to imagine the future: The prospective brain. Nature Reviews Neuroscience 8(9): 657–661.CrossRefGoogle Scholar
  92. 92.
    Ingvar, D.H. 1985. “Memory of the future”: An essay on the temporal organization of conscious awareness. Human Neurobiology 4(3): 127.Google Scholar
  93. 93.
    Tulving, E. 1985. Memory and consciousness. Canadian Psychology 26(1): 1–12.Google Scholar
  94. 94.
    Levine, B., M. Freedman, D. Dawson, S. Black, and D.T. Stuss. 1999. Ventral frontal contribution to self-regulation: Convergence of episodic memory and inhibition. Neurocase 5(3): 263–275.CrossRefGoogle Scholar
  95. 95.
    Harenski, C.L., O. Antonenko, M.S. Shane, and K.A. Kiehl. 2009. A functional imaging investigation of moral deliberation and moral intuition. Neuroimage 49: 2707–2716.CrossRefGoogle Scholar
  96. 96.
    Young, L., J.A. Camprodon, M. Hauser, A. Pascual-Leone, and R. Saxe. 2010. Disruption of the right temporoparietal junction with transcranial magnetic stimulation reduces the role of beliefs in moral judgments. Proceedings of the National Academy of Sciences 107(15): 6753.CrossRefGoogle Scholar
  97. 97.
    Scanlon, T.M. 2008. Moral dimensions: Permissibility, meaning, blame. Cambridge: Harvard University Press.Google Scholar
  98. 98.
    Edelman, G.M., and J.A. Gally. 2001. Degeneracy and complexity in biological systems. Proceedings of the National Academy of Sciences 98(24): 13763.CrossRefGoogle Scholar
  99. 99.
    Friston, K.J., and C.J. Price. 2003. Degeneracy and redundancy in cognitive anatomy. Trends in Cognitive Sciences 7(4): 151–152.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.University of Illinois at ChicagoChicagoUSA

Personalised recommendations