Pammi V S Chandrasekhar, Ruiz Sergio, Lee Sangkyun, Noussair Charles N, Sitaram Ranganatha
Centre of Behavioural and Cognitive Sciences, University of AllahabadAllahabad, India.
Laboratory for Brain-Machine Interfaces and Neuromodulation, Pontificia Universidad Católica de ChileSantiago, Chile.
Front Neurosci. 2017 Apr 27;11:237. doi: 10.3389/fnins.2017.00237. eCollection 2017.
Kahneman and Tversky (1979) first demonstrated that when individuals decide whether or not to accept a gamble, potential losses receive more weight than possible gains in the decision. This phenomenon is referred to as loss aversion. We investigated how loss aversion in risky financial decisions is influenced by sudden changes to wealth, employing both behavioral and neurobiological measures. We implemented an fMRI experimental paradigm, based on that employed by Tom et al. (2007). There are two treatments, called RANDOM and CONTINGENT. In RANDOM, the baseline setting, the changes to wealth, referred to as wealth shocks in economics, are independent of the actual choices participants make. Under CONTINGENT, we induce the belief that the changes in income are a consequence of subjects' own decisions. The magnitudes and sequence of the shocks to wealth are identical between the CONTINGENT and RANDOM treatments. We investigated whether more loss aversion existed in one treatment than another. The behavioral results showed significantly greater loss aversion in CONTINGENT compared to RANDOM after a negative wealth shock. No differences were observed in the response to positive shocks. The fMRI results revealed a neural loss aversion network, comprising the bilateral striatum, amygdala and dorsal anterior cingulate cortex that was common to the CONTINGENT and RANDOM tasks. However, the ventral prefrontal cortex, primary somatosensory cortex and superior occipital cortex, showed greater activation in response to a negative change in wealth due to individual's own decisions than when the change was exogenous. These results indicate that striatum activation correlates with loss aversion independently of the source of the shock, and that the ventral prefrontal cortex (vPFC) codes the experimental manipulation of agency in one's actions influencing loss aversion.
卡尼曼和特沃斯基（1979年）首次证明，当个体决定是否接受一场赌博时，在决策过程中潜在损失比可能的收益受到更多重视。这种现象被称为损失厌恶。我们采用行为学和神经生物学测量方法，研究了风险金融决策中的损失厌恶如何受到财富突然变化的影响。我们基于汤姆等人（2007年）采用的功能磁共振成像（fMRI）实验范式，实施了一项实验。有两种处理方式，分别称为随机（RANDOM）和依情况而定（CONTINGENT）。在随机处理方式（即基线设置）中，财富变化，在经济学中称为财富冲击，与参与者实际做出的选择无关。在依情况而定的处理方式下，我们使参与者相信收入变化是他们自己决策的结果。依情况而定和随机处理方式下财富冲击的幅度和顺序是相同的。我们研究了一种处理方式中的损失厌恶是否比另一种更多。行为学结果显示，在负财富冲击后，依情况而定处理方式下的损失厌恶明显高于随机处理方式。在对正冲击的反应中未观察到差异。功能磁共振成像结果揭示了一个神经损失厌恶网络，包括双侧纹状体、杏仁核和背侧前扣带回皮质，这在依情况而定和随机任务中是共同的。然而，腹侧前额叶皮质、初级躯体感觉皮质和枕叶上部皮质，在因个体自身决策导致财富出现负面变化时，比变化是外生的情况下，表现出更大的激活。这些结果表明，纹状体激活与损失厌恶相关，与冲击来源无关，并且腹侧前额叶皮质（vPFC）编码了个体行为中影响损失厌恶的能动性实验操作。
