Publications

Hewig et al. (2011)

The study by Hewig and colleagues investigates behavior in the ultimatum game and the dictator game. The main focus was on assessing emotional reactions related to choices in these games. The participants played both the ultimatum and the dictator game as the proposer and also as the receiver. While the participants played as receiver an electroencephalogram (EEG) and electrodermal activity (EDA) were recorded. At the end of the session participants indicated how positive or negative they perceived the offers they got as receiver. The results showed that unfair offers were rejected more often. This is not in line with the classic theory of the homo oeconomicus, which states that all human behavior is geared towards increasing one’s own gains, since rejecting an offer also means rejecting own gains. Furthermore unfair offers were also perceived as more negative which was also evident in the physiological measures. Further analysis revealed that the acceptance of an offer can be predicted using the rating of the offer (positive/negative) and reactions in the EEG and the electrodermal activity.

This study investigates the influence of facial expression on decision making in the ultimatum game. For this purpose an online experiment with 1326 participants was conducted. The subjects received ultimatum offers from smiling, neutral or angry looking proposers. For every offer the participants had to decide between accepting and rejecting it. As expected, fair offers were accepted more frequently than unfair offers. Furthermore, the facial expression of the proposer also had an influence on decision making of the receiver. Offers from smiling persons were accepted more frequently than offers from persons with a neutral facial expression. Offers from angry proposers were accepted least often. The influence of facial expression was strongest for unfair and particularly fair offers. Thus, a smile can be helpful in the next bargain!

According to rational choice theory, receivers in the ultimatum game should accept every offer they receive. Even a small amount of money is better than no money at all. In fact receivers reject, above all, unfair offers and thus behave irrationally, since they forgo their own gain. The study by Mussel and colleagues investigates the influence of need for cognition (assessed via questionnaire) and reaction time in the ultimatum game on decision making of the receiver. Here, the reaction time refers to the time it takes the receiver to reject or accept an offer. High need for cognition and longer reaction times were considered as indicators for rational decision making. All in all, offers were rejected more frequently the more unfair they were. Need for cognition and reaction time also influenced the decision making of the receiver. The higher the need for cognition, the more likely especially fair offers were accepted and unfair offers rejected. The longer the reaction time, the more offers were rejected. These results indicate that the rejection of unfair offers in the ultimatum-game cannot unconditionally be interpreted as irrational decision making.

In this study Mussel and colleagues address the influence of facial expression on decision making in the ultimatum game. Furthermore, they investigated whether facial expression influences the processing of offers in the ultimatum game. 10 men and 10 women played the ultimatum game as receivers and received offers from smiling or neutral looking proposers. During the entire game the electrical brain activity was measured via EEG. The focus was on the feedback-related negativity (FRN) which is usually more pronounced for unfair versus fair offers. Generally, unfair offers were rejected more frequently than fair offers. Additionally, somewhat unfair offers by male proposer were rejected more often than corresponding offers by female proposers. Facial expression also had a (small) influence on the decision of the receiver. Unfair offers of neutral male proposers were rejected more frequently than corresponding offers of neutral and smiling female proposers. For the FRN, the well-known effect of larger negativity following unfair vs. fair offers could be replicated. The increase in negativity from fair to unfair offers was less pronounced for smiling proposers, though. Thus, the FRN following unfair offers was smaller for smiling versus neutral proposers. Taken together, the FRN and behavioral results show that a smiling face leads to more positive reactions to unfair offers than a neutral face.

In this study, Rodrigues and colleagues investigated the impact of altruism on offers in dictator game and the linked brain activity measured via electroencephalogram (EEG). Participants were selected via online screening to score high or low on altruism, then they participated in a dictator game and as a second step in a fairness rating of offers of other dictators to receivers. Additional to the expected behavior effect, that high altruistic dictators offered more money to the receivers, there was a higher midfrontal theta activity in high altruistic people before making fair offers, while there was a higher midfrontal theta activity in low altruistic persons before their own unfair offers. There was no difference in fairness rating between these two groups.

These results suggest, that high altruistic people may offer more to receivers in dictator game due to empathic reasons, while the higher midfrontal theta activity of the low altruistic persons in combination with the same fairness ratings as the high altruistic persons may indicate a negative rating and feeling about the decision they are going to make. 

Osinsky et al. (2013)

In this study Osinsky and colleagues investigate the feedback-related negativity (FRN) following unfair versus fair offers in the ultimatum game. Previous studies have shown that unfair offers lead to a larger negativity in the voltage measured via EEG compared to fair offers. Thus the FRN can be interpreted as a marker for a good vs. bad evaluation of an event. The aim of the current study was to find out whether the FRN is also present in learning in the ultimatum game. More specifically the participants had to learn which of the proposers made fair and which made unfair offers. Throughout the course of the experiment a larger negativity in the EEG was also elicited by the faces of unfair proposers even before their offers were shown. According to this result a negative feeling is associated with the faces of unfair proposers in the process of the experiment.

Weiland et al. (2012)

The article by Weiland and colleagues is about the neuronal basis of behavior in bargaining situations, especially focusing on making offers. In their study participants’ brain activity was measured using functional magnetic resonance imaging (fMRI) while playing the ultimatum game and the dictator game. In both games the participants assumed the role of the proposer who repeatedly divides a fixed amount of money between himself and another player (the receiver). In the ultimatum game, the receiver decides whether he accepts the offer or not, only if he accepts the offer the money is distributed accordingly (else neither the receiver nor the proposer receive any money). In the dictator game the receiver has no choice, the offer is always accepted. Weiland and colleagues showed that fair offers (equal split of the amount of money or only slight advantage for the proposer) result in different brain activation in the ultimatum game compared to the dictator game. In the ultimatum game there was a higher activation of regions in the prefrontal cortex whilst in the dictator game the dorsal anterior and posterior cingulate cortex were more active. The different active areas are suggestive of different motives behind fair offers in the two games. The results in the ultimatum game indicate strategic reasons behind the fair offers, their main goal being the maximization of one’s own win. On the other hand, fair offers in the dictator game seem to be due to altruistic behavior which is not motivated by maximizing one’s wins.

Hewig et al. (2012)

Adolescents show risky behavior in several contexts. This might be due to brain development. Brain areas responsible for behavioral control are not fully developed until late adolescence. But brain areas processing rewards show increased activity during adolescence.

The processing of reward and punishment in the brain can be measured via electroencephalography (EEG) amongst others. In the context of reward and punishment processing the so called feedback-related negativity (FRN) is of special interest. This refers to a negativity in the ongoing voltage following negative feedback (e.g. loss, incorrect action) compared to positive feedback (e.g. win, correct action). One experimental task which can be used to investigate the FRN is the so called BART (= Balloon Analogue Risk Task). In this task the participants repeatedly have to decide whether they want to further inflate a virtual balloon to double their current win or save the current win and transfer it to a virtual account. If the balloon bursts during inflation the current win is lost. In an ongoing study the FRN in the BART is investigated in male adolescents (13-16 years). The results will lead to a better understanding of the relation between the processing of reward/punishment and risky behavior in adolescence.

Hewig et al. (2011)

This study by Hewig and colleagues deals with two event-related potentials in the electroencephalogram (EEG), the error-related negativity (ERN) and the error-positivity (Pe). Both can be observed as voltage changes in the EEG after an erroneous action. The current study focused on the relation between these two event-related potentials and the conscious detection of the error. To investigate this topic, participants repeatedly had to enter five-digit numbers into the computer. After each number, participants had to indicate whether they had entered the number correctly, wrong, or were unsure about it. The results showed that the ERN was largest following errors the participants were aware of (i.e. numbers where participants stated that they had entered them wrong). Trials with wrong numbers that were not perceived as such (i.e.  participants stated that the number was correct or they were unsure) as well as trials with correct numbers resulted in a smaller ERN. Similar to the ERN the Pe was largest following consciously recognized errors. However trials in which participants were not sure whether they were correct (regardless of whether they were actually correct or not) also resulted in a larger Pe. According to these results the ERN can be interpreted as an indicator of a consciously recognized difference between a planned action and the actual action, which also elicits a Pe. Furthermore a Pe is also elicited if the result of the comparison of planned and actual action is unclear, that is when one is not sure that the action was correct.

Kreussel et al. (2012)

The study by Kreussel and colleagues deals with various factors influencing the feedback-related negativity (FRN). This refers to a change in the voltage measured via electroencephalography (EEG) in the form of a larger negativity following negative feedback (e.g. loss) compared to positive feedback (e.g. win). The factors were investigated using a reinforcement-learning task during which participants repeatedly had to choose one of two simultaneously presented virtual stimuli which, depending on the chosen stimulus, could result either in a loss or a win. Each stimulus stood for a combination of possible outcome (win vs. loss), probability of the occurrence of the possible outcome and amount of money to be won or lost (10 cents vs. 40 cents). While the participants completed this task an EEG was recorded. The results showed that the FRN is influenced by all investigated factors.

Osinsky et al. (2012)

In this study Osinsky and colleagues investigated the influence of previous outcomes on the processing of the current result in a game of chance. To do that, voltages from the scalp were recorded via electroencephalography (EEG) allowing conclusions concerning active brain areas. Three changes in the ongoing voltage related to the processing of wins and losses were of special interest: the feedback-related negativity (FRN) as well as the P200 and the P300. The results showed that all three of them are not only influenced by the current outcome but also by the two preceding outcomes. Both the FRN and the P300 are larger if the two previous outcomes differ from the current outcome (e.g. in outcome sequences of win-win-loss and loss-loss-win). The P200 is larger in the context of two preceding wins compared to other preceding outcome sequences.

Schmidt et al. (2013)

This article deals with the relationship between arousal and risky behavior. Several theories of personality propose that there is an optimal level of arousal. If the current arousal is below this level people seek stimulation in order to bring their arousal closer to the optimum. Risky behavior in gambling is an example for such stimulation. The study described in the article showed that resting heart rate (which can be interpreted as a measure for arousal in the sense of a personality trait) is related to risky behavior in gambling. The lower the resting heart rate of the participants the riskier was their gambling behavior. At the same time these participants found the risky options in the gambling to be less risky and arousing compared to participants with higher resting heart rate. To check whether this relation also holds for situational arousal, every participant played the game of chance twice. Before one of the occasions, the participants spent a 10-minute training session on a bicycle ergometer to increase arousal. This led to less risky behavior in the gamble compared to the occasion without ergometer training. Thus the results indicated that general as well as momentary arousal is inversely related to risky behavior.