Alec Smith

Triangulating the Neural, Psychological, and Economic Bases of Guilt Aversion

VIDEO ABSTRACT Why do people often choose to cooperate when they can better serve their interests by acting selfishly? One potential mechanism is that the anticipation of guilt can motivate cooperative behavior. We utilize a formal model of this process in conjunction with fMRI to identify brain regions that mediate cooperative behavior while participants decided whether or not to honor a partners trust. We observed increased activation in the insula, supplementary motor area, dorsolateral prefrontal cortex (PFC), and temporal parietal junction when participants were behaving consistent with our model, and found increased activity in the ventromedial PFC, dorsomedial PFC, and nucleus accumbens when they chose to abuse trust and maximize their financial reward. This study demonstrates that a neural system previously implicated in expectation processing plays a critical role in assessing moral sentiments that in turn can sustain human cooperation in the face of temptation.

Irrational exuberance and neural crash warning signals during endogenous experimental market bubbles

Significance Asset price bubbles are an important example of human group decision making gone awry, but the behavioral and neural underpinnings of bubble dynamics remain mysterious. In multisubject markets determined by 11–23 subjects, with 2–3 subjects simultaneously scanned using functional MRI, we show how behavior and brain activity interact during bubbles. Nucleus accumbens (NAcc) activity tracks the price bubble and predicts future price changes. Traders who buy more aggressively based on NAcc signals earn less. High-earning traders have early warning signals in the anterior insular cortex before prices reach a peak, and sell coincidently with that signal, precipitating the crash. These experiments could help understand other cases in which human groups badly miscompute the value of actions or events. Groups of humans routinely misassign value to complex future events, especially in settings involving the exchange of resources. If properly structured, experimental markets can act as excellent probes of human group-level valuation mechanisms during pathological overvaluations—price bubbles. The connection between the behavioral and neural underpinnings of such phenomena has been absent, in part due to a lack of enabling technology. We used a multisubject functional MRI paradigm to measure neural activity in human subjects participating in experimental asset markets in which endogenous price bubbles formed and crashed. Although many ideas exist about how and why such bubbles may form and how to identify them, our experiment provided a window on the connection between neural responses and behavioral acts (buying and selling) that created the bubbles. We show that aggregate neural activity in the nucleus accumbens (NAcc) tracks the price bubble and that NAcc activity aggregated within a market predicts future price changes and crashes. Furthermore, the lowest-earning subjects express a stronger tendency to buy as a function of measured NAcc activity. Conversely, we report a signal in the anterior insular cortex in the highest earners that precedes the impending price peak, is associated with a higher propensity to sell in high earners, and that may represent a neural early warning signal in these subjects. Such markets could be a model system to understand neural and behavior mechanisms in other settings where emergent group-level activity exhibits mistaken belief or valuation.

Hold‐Up: With a Vengeance

When contracts are incomplete or unenforceable, inefficient levels of investment may occur because of hold-up. If individuals care for negative reciprocity, these problems may be reduced, as revenge becomes a credible threat. However, negative reciprocity has this effect only when the investor holds the rights of control of the investment proceeds. We explore this issue analytically, deriving predictions for hold-up games which differ as regards assignment of rights of control. We also test and support these predictions in an experiment.

Social emotions and psychological games

Emotions arise from cognitive appraisals and organize adaptive behavioral responses. The appraisals associated with social emotions such as guilt and anger can be modeled with utility functions that depend on both material and psychological payoffs, and their effect on behavior can be mathematically described using game theory. Guilt arises from the belief that an agent has disappointed a relationship partner and motivates reparative actions, while anger arises from the frustration of a goal being unexpectedly blocked and motivates aggressive actions. These psychological payoffs not only enable cooperation, but also appear to be associated with neural activations consistent with negative affective states. We believe integrating appraisal theory with game theoretic modeling can improve our ability to study emotions and predict behavior in social interactions.

Case report of syncope during a transcranial direct current stimulation experiment in a healthy adult participant

We report the following syncope case observed during a transcranial direct current stimulation (tDCS) study. There are no known cases of syncope during tDCS with human participants [1,2]. The participant was a healthy, 23 year old female. In the prescreening questionnaire she disclosed no history of prior closed head injury, loss of consciousness, family history of epilepsy, or history of seizures or febrile seizures [3,4]. The only medication that she reported taking was the oral contraceptive Lutera. On the day of the event, the participant reported no additional risk factors such as sleep pattern changes or deprivation, changes in food and water consumption, medication changes, occult drug use, or high doses of caffeine. Cathodal tDCS stimulation was delivered over the right temporoparietal junction (CP6) with an intensity of 2mA using a 4 1 ring electrodemontage.We used a neuroConn DC-Stimulator MC (München, Germany) to administer the stimulation. The participant had not previously undergone tDCS. The setting was an on-campus research lab that conducts nonclinical decision making experiments. The participant was seated on a chair with her back supported and both feet on the floor. The event occurred about 1min into the stimulation procedure. The participant informed the experimenters that she felt nauseous and dizzy, and the experimenters asked the participant if she was feeling all right and if she would like to continue. The participant responded that she wanted to stop the procedure and the experimenters terminated the stimulation immediately. The participant fainted a few seconds after the stimulation was discontinued. The time elapsed from the first moment the participant indicated that she felt nauseous and dizzy to the moment that the participant lost consciousness was approximately 30 seconds. The experimenters caught the participant to prevent injury and laid her down on the floor. The experimenters noted no obvious physical symptoms besides loss of consciousness. After about 10 seconds, the participant revived, sat up, and responded when spoken to. The participant was able to identify correctly where she was, and reported that she believed that she had fallen asleep. After the participant regained consciousness the experimenters noted the pallor in her face but did not check pulse and blood pressure. After about 30 minutes of observation with no symptoms of nausea or dizziness the participant left the laboratory. She was withdrawn from the study and did not undergo further tDCS testing. In a follow-up survey, the participant informed the experimenters that she experienced anxiety before the stimulation related to the syringes used to fill the electrode holders with electroconductive gel during the application of the electrodes. She also