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Emotionen und Risikoexponierung: Der Einfluss positiver und negativer Affekte auf Portfolioentscheidungen

Ibrahim Filiz

sofia Diskussionsbeiträge 2018, No. 3 https://doi.org/10.46850/sofia.9783941627673

Diese experimentelle Untersuchung wendet sich der Frage zu, ob positive und negative Affekte einen Einfluss auf das Diversifikationsverhalten haben. Dabei zeigt sich, dass nur ein kleiner Teil der Probanden dem Rationalkalkül folgt und stets das optimale Portfolio wählt. Ferner zeigt sich, dass die Stimmungs-lage der Wirtschaftssubjekte einen Einfluss auf ihre Portfolioentscheidungen und somit auch auf ihre Risikoexponierung hat. Das durchschnittliche Risiko der Portfolios – gemessen an der Standardabweichung der Renditen – fällt im Treatment „Neutral“ deutlich niedriger aus als im Treatment „Positiv“ und im Treatment „Negativ“.

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References

  1. Ackert, L. S. / Mazzotta, S. / Qi, L. (2011): An Experimental Investigation of Asset Pricing in Segmented Markets, Southern Economic Journal 77(3),585-598. DOI: https://doi.org/10.4284/sej.2011.77.3.585.
  2. Ackert, L. S. / Church, B. K. / Qi, L. (2015): An Experimental Examination of Portfolio Choice, Review of Finance, 19(5), 1-21.
  3. Agnew, J., Balduzzi, P., Sundén, A. (2003): Portfolio choice and trading in a large 401(k) plan, American Economic Review, 93(1), 193-215. DOI: https://doi.org/10.1257/000282803321455223.
  4. Anderson, A. (2013): Trading and Under-Diversification, Review of Finance, 17(5), 1699-1741. DOI: https://doi.org/10.1093/rof/rfs044.
  5. Andrade, E. B. / Odean, T. / Lin, S. (2016): Bubbling with Excitement: An Experiment, Review of Finance, 20(2), 1-20. DOI: https://doi.org/10.1093/rof/rfv016.
  6. Apergis, N. / Gabrielsen, A. / Smales, L. A. (2016): (Unusual) Weather and Stock Returns—I Am Not in the Mood for Mood: Further Evidence from International Markets, Financial Markets and Portfolio Management, 30(1), 63-94. DOI: https://doi.org/10.1007/s11408-016-0262-z.
  7. Baker, M. / Wurgler, J. (2007): Investor Sentiment in the Stock Market, Journal of Economic Perspectives, 21(2), 129–151. DOI: https://doi.org/10.1257/jep.21.2.129.
  8. Baltussen, G. / Post, G. T. (2011): Irrational Diversification: An Examination of Individual Portfolio Choice, Journal of Financial and Quantitative Analysis, 46(5), 1463–1491. DOI: https://doi.org/10.1017/S002210901100041X.
  9. Barber, B. M., Odean, T. (2000): Trading is Hazardous to your Wealth: The Common Stock Investment Performance of Individual Investors, Journal of Finance, 55(2), 773-806. DOI: https://doi.org/10.1111/0022-1082.00226.
  10. Bassi, A. / Colacito, R. / Fulghieri, P. (2013): O Sole Mio: An Experimental Analysis of Weather and Risk Attitudes in Financial Decisions, Review of Financial Studies, 26(7), 1824-1852. DOI: https://doi.org/10.1093/rfs/hht004.
  11. Baumeister, R. F. / Vohs, K. D. / DeWall, C. N. / Zhang, L. (2007): How Emotion Shapes Behavior: Feedback, Anticipation, and Reflection, rather than Direct Causation, Personality and Social Psychology Review, 11(2), 167-203. DOI: https://doi.org/10.1177%2F1088868307301033.
  12. Benartzi, S. (2001): Excessive Extrapolation and the Allocation of 401(k) Accounts to Company Stock, Journal of Finance, 56(5), (2001), 1747-1764. DOI: https://doi.org/10.1111/0022-1082.00388.
  13. Benartzi, S. / Thaler, H. (2001): Naive Diversification Strategies in Defined Contribution Saving Plans, American Economic Review, 91(1), 79-98. DOI: https://doi.org/10.1257/aer.91.1.79.
  14. Bless, H. / Schwarz, N. / Kemmelmeier, M. (1996): Mood and Stereotyping: The Impact of Moods on the use of General Knowledge Structures, European Review of Social Psychology 7(1), 63-93. DOI: https://doi.org/10.1080/14792779443000102.
  15. Blume, M. E., Friend, I. (1975): The Asset Structure of Individual Portfolios and some Implications for Utility Functions, Journal of Finance, 30(2), 585-603. DOI: https://doi.org/10.1111/j.1540-6261.1975.tb01833.x.
  16. Bode, M., van Echelpoel, A., Sievi, C. R. (1994): Multinationale Diversifikation: Viel zitiert, kaum befolgt, Die Bank, 94(4), 202-206.
  17. Breaban, A. / Noussair, C. N. (2018): Emotional State and Market Behavior, Review of Finance, 22(1), 279–309. DOI: https://doi.org/10.1093/rof/rfx022.
  18. Cao, M. / Wei, J. (2005): Stock Market Returns: A Note on Temperature Anomaly, Journal of Banking and Finance, 29(6), 1559–1573. DOI: https://doi.org/10.1016/j.jbankfin.2004.06.028
  19. Chang, S. C. / Chen, S. S. / Chou, R. K. / Lin, Y. H. (2008): Weather and Intra-day Patterns in Stock Returns and Trading Activity, Journal of Banking and Finance, 32(9), 1754-1766. DOI: https://doi.org/10.1016/j.jbankfin.2007.12.007.
  20. Chang, T. / Nieh, C. C. / Yang, M. J. / Yang, T. Y. (2006): Are Stock Market Returns Related to the Weather Effects? Empirical evidence from Taiwan, Physica A: Statistical Mechanics and its Applications, 364, 343–354. DOI: https://doi.org/10.1016/j.physa.2005.09.040.
  21. Conte, A. / Levati, M. V. / Nardi, C. (2018): Risk Preferences and the Role of Emotions, Economica, 85(338), 305-328. DOI: https://doi.org/10.1111/ecca.12209.
  22. Daniel, K. / Hirshleifer, D. / Teoh, S. H. (2002): Investor Psychology in Capital Markets: Evidence and Policy Implications, Journal of Monetary Eco-nomics, 49(1), 139-209. DOI: https://doi.org/10.1016/S0304-3932(01)00091-5.
  23. De Bondt, W. F. M. (1998): A Portrait of the Individual Investor, European Economic Review, 42(3-5), 831-844. DOI: https://doi.org/10.1016/S0014-2921(98)00009-9.
  24. Dowling, M. / Lucey, B. M. (2005): Weather, Biorhythms, Beliefs and Stock Returns – some preliminary Irish evidence, International Review of Financial Analysis, 14(3), 337–355. DOI: https://doi.org/10.1016/j.irfa.2004.10.003.
  25. Elster, J. (1998): Emotions and Economic Theory, Journal of Economic Literature, 36 (1), 47–74.
  26. Elster, J. (1996): Rationality and the Emotions, The Economic Journal, 106(438), 1386-1397. DOI: https://doi.org/10.2307/2235530.
  27. Eyster, E. / Weizsäcker, G. (2010): Correlation Neglect in Financial Decision-Making, DIW Discussion Paper, Nr. 1104. DOI: https://doi.org/10.2139/ssrn.1735339.
  28. Fernandes, D. (2013): The 1/N Rule Revisited: Heterogeneity in the Naïve Diversification Bias, International Journal of Research in Marketing, 30(3), 310–313. DOI: https://doi.org/10.1016/j.ijresmar.2013.04.001.
  29. Filiz, I. / Nahmer, T. / Spiwoks, M. / Bizer, K. (2018): Portfolio Diversification: The Influence of Herding, Status-quo Bias, and the Gambler’s Fallacy, Financial Markets and Portfolio Management, 32(2), 167-205. DOI: https://doi.org/10.1007/s11408-018-0311-x.
  30. Fischbacher, U. (2007): Z-Tree: Zurich Toolbox for Ready-Made Economic Experiments, Experimental Economics, 10(2) , 171–178. DOI: https://doi.org/10.1007/s10683-006-9159-4.
  31. Floros, C. (2011): On the Relationship between Weather and Stock Market Returns, Studies in Economics and Finance, 28(1), 5-13. DOI: https://doi.org/10.1108/10867371111110525.
  32. Forgas, J. P. (1998): On being Happy and Mistaken: Mood Effects on the Fundamental Attribution Error, Journal of Personality and Social Psychology, 75(2), 318-331. DOI: https://doi.apa.org/doi/10.1037/0022-3514.75.2.318.
  33. French, K. R. / Poterba, J. M. (1991): Investor Diversification and International Equity Markets, American Economic Review, 81(2), 222-226. DOI: https://doi.org/10.3386/w3609.
  34. Gambetti, E. / Giusberti, F. (2012): The Effect of Anger and Anxiety Traits on Investment Decisions, Journal of Economic Psychology, 33 (6), 1059-1069. DOI: https://doi.org/10.1016/j.joep.2012.07.001.
  35. George, J. M. / Dane, E. (2016): Affect, emotion, and decision making, Organizational Behavior and Human Decision Processes, 136, 47–55. DOI: https://doi.org/10.1016/j.obhdp.2016.06.004.
  36. Goetzmann, W. N. / Kumar, A. (2008): Equity Portfolio Diversification, Review of Finance, 12(3), 433-463. DOI: https://doi.org/10.1093/rof/rfn005.
  37. Grablea, J. E. / Roszkowskib, M. J. (2008): The Influence of Mood on the Willingness to Take Financial Risks, Journal of Risk Research, 11(7), 905-923. DOI: https://doi.org/10.1080/13669870802090390.
  38. Gross, J. J. / Levenson, R. W. (1995): Emotion Elicitation Using Films, Cognition and Emotion, 9(1), 87-108. DOI: https://doi.org/10.1080/02699939508408966.
  39. Gubaydullina, Z. / Spiwoks, M. (2015): Correlation Neglect, Naïve Diversification, and Irrelevant Information as Stumbling Blocks for Optimal Diversification, Journal of Finance & Investment Analysis, 4 (2), 1-19.
  40. Guiso, L. / Haliassos, M., / Jappelli, T. (2002): Household Portfolios, MIT Press, Cambridge. DOI: https://doi.org/10.7551/mitpress/3568.001.0001.
  41. Hedesström, T. M. / Svedsäter, H. / Gärling, T. (2006): Covariation Neglect Among Novice Investors, Journal of Experimental Psychology: Applied 12 (3), 155-165. DOI: https://doi.apa.org/doi/10.1037/1076-898X.12.3.155.
  42. Hibbert, A. M. / Lawrence, E. R. / Prakash, A. J. (2012): Can Diversification be Learned?, The Journal of Behavioral Finance, 13(1), 38-50. DOI: https://doi.org/10.1080/15427560.2012.654547.
  43. Hirshleifer, D. (2001): Investor Psychology and Asset Pricing, 56(4), 1533-1597. DOI: https://doi.org/10.1111/0022-1082.00379.
  44. Hirshleifer, D. / Shumway, T. (2003): Good day sunshine: Stock returns and the weather, Journal of Finance, 58 (3), 1009-1032. DOI: https://doi.org/10.1111/1540-6261.00556.
  45. Holt, C. A. / Laury, S. K. (2002): Risk Aversion and Incentive Effects, American Economic Review 92(5), 1644-1655. DOI: https://doi.org/10.1257/000282802762024700.
  46. Huber, J. / Kirchler, M. / Stöckl, T. (2010): The Hot Hand Belief and the Gambler’s Fallacy in Investment Decisions under Risk, Theory and Decision, 68(4), 445–462. DOI: https://doi.org/10.1007/s11238-008-9106-2.
  47. Huberman, G. / Sengmueller, P. (2004): Performance and Employer Stock in 401(k) Plans, Review of Finance, 8(3), 403–443. DOI: https://doi.org/10.1007/s10679-004-2544-y.
  48. Ifcher, J. / Zarghamee, H. (2011): Happiness and Time Preference: The Effect of Positive Affect in a Random-Assignment Experiment, American Eco-nomic Review, 101(7), 3109-29. DOI: https://doi.org/10.1257/aer.101.7.3109.
  49. Ifcher, J / Zarghamee, H. (2014): Affect and Overconfidence: A Laboratory Investigation. Journal of Neuroscience, Psychology, and Economics, 7(3), 125-150. DOI: https://doi.apa.org/doi/10.1037/npe0000022.
  50. Isen, A. (2000): Positive Affect and Decision Making, in Lewis, M. / Haviland-Jones, J., Handbook of Emotion, New York.
  51. Johnson, E. J. / Tversky, A. (1983): Affect, Generalization, and the Perception of Risk, Journal of Personality and Social Psychology, 45(1), 20–31. DOI: https://doi.apa.org/doi/10.1037/0022-3514.45.1.20.
  52. Kallir, I / Sonsino, D. (2009): The Neglect of Correlation in Allocation Deci-sions. Southern Economic Journal, 75(4), 1045-1066.
  53. Kamstra, M. J. / Kramer, L. A. / Levi, M. D. (2003): Winter blues: A SAD stock market cycle, American Economic Review, 93(1), 324-343. DOI: https://doi.org/10.1257/000282803321455322.
  54. Kang, S. H. / Jiang, Z. / Lee, Y. / Yoon, S.-M. (2010): Weather Effects on the Returns and Volatility of the Shanghai Stock Market, Physica A: Statis-tical Mechanics and its Applications, 389(1), 91-99. DOI: https://doi.org/10.1016/j.physa.2009.09.010.
  55. Kaustia, M. / Rantapuska, E. (2016): Does Mood Affect Trading Behavior?, Journal of Financial Markets, 29, 1-26. DOI: https://doi.org/10.1016/j.finmar.2015.08.001.
  56. Keef, S. P. / Roush, M. L. (2007): Daily Weather Effects on the Returns of Australian Stock Indices, Applied Financial Economics, 17(3), 173–184. DOI: https://doi.org/10.1080/09603100600592745.
  57. Kelly, M. (1995): All their eggs in one basket: portfolio diversification in U.S. households, Journal of Economic Behavior and Organization, 27, 87–96. DOI: https://doi.org/10.1016/0167-2681(95)00006-E.
  58. Kim, J. H. (2017): Stock Returns and Investors’ Mood: Good Day Sunshine or Spurious Correlation?, International Review of Financial Analysis, 52, 94-103. DOI: https://doi.org/10.1016/j.irfa.2017.05.004.
  59. Kirchsteiger, G. / Rigottii, L. / Rustichini, A. (2006): Your Morals Might be your Moods, Journal of Economic Behavior and Organization, 59, 155-172. DOI: https://doi.org/10.1016/j.jebo.2004.07.004.
  60. Kliger, D. /Levy, O. (2003): Mood-induced variation in risk preferences, Journal of Economic Behavior and Organization, 52, 573–584. DOI: https://doi.org/10.1016/S0167-2681(03)00069-6.
  61. Krämer, W. / Runde, R. (1997): Stocks and the Weather: An Exercise in Data Mining or Yet Another Capital Market Anomaly?, Empirical Economics, 22(4), 637-641. DOI: https://doi.org/10.1007/BF01205784.
  62. Krivelyova, A. / Robotti, C. (2003): Playing the Field: Geomagnetic Storms and International Stock Markets, Working Paper Federal Reserve Bank of Atlanta, 2003-5.
  63. Kuhnen, C. M. / Knutson, B. (2011): The Influence of Affect on Beliefs, Preferences, and Financial Decisions, Journal of Financial and Quantitative Analysis, 46(3), 605-626. DOI: https://doi.org/10.1017/S0022109011000123.
  64. Lahav, Y. / Meer, S. (2012): The Effect of Induced Mood on Prices in Asset Markets - Experimental Evidence, Working Paper, Ben-Gurion University of the Negev. DOI: https://doi.org/10.2139/ssrn.2050299.
  65. Lease, R. C. / Lewellen, W. G. / Schlarbaum, G. G. (1974): The Individual Investor: Attributes and Attitudes. Journal of Finance, 29(2), 413–433. DOI: https://doi.org/10.1111/j.1540-6261.1974.tb03055.x.
  66. Lee, C. J. / Andrade, E. B. (2014): Fear, Excitement, and Financial Risk-Taking, Cognition and Emotion, 29(1), 178-187. DOI: https://doi.org/10.1080/02699931.2014.898611.
  67. Lee, C. J. / Andrade, E. B. (2011): Fear, Social Projection, and Financial Decision Making, Journal of Marketing Research, 48(SPL), 121-129. DOI: https://doi.org/10.1509%2Fjmkr.48.SPL.S121.
  68. Leith, K. P. / Baumeister, R. F. (1996): Why do Bad Moods Increase Self-Defeating Behavior? Emotion, Risk Tasking, and Self-Regulation, Journal of Personality and Social Psychology, 71(6), 1250-1267. DOI: https://doi.apa.org/doi/10.1037/0022-3514.71.6.1250.
  69. Lerner J. S. / Keltner D. (2001): Fear, Anger and Risk, Journal of Personality and Social Psychology, 81(1), 146-159. DOI: https://doi.apa.org/doi/10.1037/0022-3514.81.1.146.
  70. Lerner, J. S. / Li, Y. / Valdesolo, P. / Kassam, K. S. (2015): Emotion and Decision Making, Annual Review of Psychology, 66(1), 799-823. DOI: https://doi.org/10.1146/annurev-psych-010213-115043.
  71. Loewenstein, G. (2000): Emotions in Economic Theory and Economic Behavior, American Economic Review, 90(2), 426-432. DOI: https://doi.org/10.1257/aer.90.2.426.
  72. Loewenstein, G. / Weber, E. / Hsee, C. / Welch, N. (2001): Risk as Feelings, Psychological Bulletin 127(2), 267–286. DOI: https://doi.apa.org/doi/10.1037/0033-2909.127.2.267.
  73. Lu, J. / Chou, R. K. (2012): Does the Weather have Impacts on Returns and Trading Activities in Order-Driven Stock Markets? Evidence from China, Journal of Empirical Finance, 19(1), 79–93. DOI: https://doi.org/10.1016/j.jempfin.2011.10.001.
  74. Lucey, B. M. / Dowling, M. (2005): The Role of Feelings in Investor Decision-Making, Journal of Economic Surveys, 19(2), 211–237. DOI: https://doi.org/10.1111/j.0950-0804.2005.00245.x.
  75. Markowitz, H. (1952): Portfolio selection, Journal of Finance, 7(1), S. 77-91. DOI: https://doi.org/10.1111/j.1540-6261.1952.tb01525.x.
  76. Meulbroek, L. (2005): Company Stock in Pension Plans: How Costly Is It?, Journal of Law & Economics, 48(2), 443–474. DOI: https://doi.org/10.1086/430807.
  77. Mitchell, O. S. / Utkus, S. P. (2002): The Role of Company Stock in Defined Contribution Plans, National Bureau of Economic Research, Working Paper 9250. DOI: https://doi.org/10.3386/w9250.
  78. Mirza, H. H. / Asghar, A. / Jam e Kausar, M. / Mushtaq, N (2012): Stock Market Returns and Weather Anomaly: Evidence from an Emerging Economy, Journal of Economics and Behavioral Studies, 4(5), 239-244. DOI: https://doi.org/10.22610/jebs.v4i5.323.
  79. Morrin, M. / Inman, J. J. / Broniarczyk, S. M. / Nenkov, G. Y. / Reuter, J. (2012): Investing for Retirement: The Moderating Effect of Fund Assortment Size on the 1/N Heuristic, Journal of Marketing Research, 49(4), 537–550. DOI: https://doi.org/10.1509%2Fjmr.08.0355.
  80. Nofsinger, J. R. (2005): Social Mood and Financial Economics, The Journal of Behavioral Finance 6(3), 144–160. DOI: https://doi.org/10.1207/s15427579jpfm0603_4.
  81. Oswald, A. / Proto, E. / Sgroi D. (2015): Happiness and Productivity, Journal of Labor Economics, 33(4), 789-822. DOI: https://doi.org/10.1086/681096.
  82. Pardo A. / Enric V. (2002): Spanish Stock Returns: Where is the Weather Effect?, European Financial Management, 9(1), 117-126.  DOI: https://doi.org/10.1111/1468-036X.00210.
  83. Pham, M. T. (2007): Emotion and Rationality: A Critical Review and Interpretation of Empirical Evidence, Review of General Psychology, 11(2), 155–78. DOI: https://doi.org/10.1037%2F1089-2680.11.2.155.
  84. Polkovnichenko, V. (2005): Household Portfolio Diversification: a case for Rank-Dependent Preferences, Review of Financial Studies, 18(4), 1467–1502. DOI: https://doi.org/10.1093/rfs/hhi033.
  85. Poterba, J. M. (2003): Employer Stock and 401(k) Plans, American Economic Review, 93(2), 398-404. DOI: https://doi.org/10.1257/000282803321947416.
  86. Rottenberg, J. / Ray, R. D. / Gross, J. J. (2007): Emotion Elicitation Using Films, in: Coan, J. A. / Allen, J. J. B., the Handbook of Emotion Elicitation and Assessment, London, 9–28.
  87. Schaefer, A. / Nils, F. / Sanchez, X. / Philippot, P. (2010): Assessing the Effectiveness of a Large Database of Emotion-Eliciting Films: A new Tool for Emotion Researchers, Cognition and Emotion, 24 (7), 1153-1172. DOI: https://doi.org/10.1080/02699930903274322.
  88. Saunders, E. M. (1993): Stock Prices and Wall Street weather, American Eco-nomic Review 83(5), 1337–1345.
  89. Schwarz, N. (2000): Emotion, Cognition, and Decision Making, Cognition & Emotion, 14(4), 433–440. DOI: https://doi.org/10.1080/026999300402745.
  90. Shiv, B. / Loewenstein, G. / Bechara, A. / Damasio, H. / Damasio, A. R. (2005): Investment Behavior and the Negative Side of Emotion, 16(6), 435-439.
  91. Shu, H.-C. (2010): Investor mood and financial markets, Journal of Economic Behavior & Organization, 76(2), 267-282. DOI: https://doi.org/10.1016/j.jebo.2010.06.004.
  92. Shu, H.-C. / Hung, M. W. (2009): Effect of Wind on Stock Market Returns: Evidence from European Markets, Applied Financial Economics, 19(11), 893–904. DOI: https://doi.org/10.1080/09603100802243766.
  93. Stanton, S. J. / Reeck, C. / Huettel, S. A. / Labar, K. S. (2014): Effects of induced mood on economics choices, Judgmend and Decision Making, 9(2), 167-175.
  94. Symeonidis, L. / Daskalakis, G. / Markellos, R. N. (2010): Does the Weather Affect Stock Market Volatility?“ Finance Research Letters, 7(4), 214-223. DOI: https://doi.org/10.1016/j.frl.2010.05.004.
  95. Stöckl, T. / Huber, J. / Kirchler, M. / Lindner, F. (2015): Hot Hand and Gambler’s Fallacy in Teams: Evidence from Investment Experiments, Journalof Economic Behavior and Organization, 117, 327–339. DOI: https://doi.org/10.1016/j.jebo.2015.07.004.
  96. Tiedens, L. Z. / Linton, S. (2002): Judgment under Emotional Certainty and Uncertainty: The Effects of Specific Emotions on Information Processing, Journal of Personality and Social Psychology, 81(6), 973-988. DOI: https://doi.apa.org/doi/10.1037/0022-3514.81.6.973.
  97. Tufan, E. / Hamarat, B. (2004): Do Cloudy Days Affect Stock Exchange Re-turns: Evidence from the Istanbul Stock Exchange, Journal of Naval Science and Engineering, 2(1), 117–26.
  98. Vohs, K. / Baumeister, R. / Loewenstein, G. (2007): Do emotions help or hurt decision making? A hedgefoxian perspective, New York.
  99. Weber, E. U. / Siebenmorgen, N. / Weber, M. (2005): Communication Asset Risk: How Name Recognition and the Format of Historic Volatility In-formation Affect Risk Perception and Investment Decisions, Risk Analysis, 25(3), 597–609. DOI: https://doi.org/10.1111/j.1539-6924.2005.00627.x.
  100. Westermann, R. / Spies, K. / Stahl, G. / Hesse, A. (1996): Relative Effectiveness and Validity of Mood Induction Procedures: A Meta-Analysis, Europe-an Journal of Social Psychology, 26(4), 557–580. DOI: https://doi.org/10.1002/(SICI)1099-0992(199607)26:4%3C557::AID-EJSP769%3E3.0.CO;2-4.
  101. Yuen, K. S .L. / Lee, T. M. C. (2003): Could Mood State Affect Risk-Taking Decisions? Journal of Affective Disorders, 75(1), 11-18. DOI: https://doi.org/10.1016/S0165-0327(02)00022-8.