Event-related potentials in response to cheating and cooperation in a social dilemma game

Does Expecting Matter? The Impact of Experimentally Established Expectations on Subsequent Memory Retrieval of Emotional Words

Previous studies have confirmed that different degrees of expectation, including the bipolarity of the expected and unexpected, as well as an intermediate level (no expectation), can affect memory. However, only a few investigations have manipulated expectation through experimentally established schema, with no consideration of how expectation impacts both item and source memory. Furthermore, stimulus emotionality may also impact memory. Therefore, we conducted a study to investigate the effects of three levels of expectation on item and source memory while considering the impact of stimulus emotionality. The experiment began with a phase dedicated to learning the rules. In the subsequent study phase, negative and neutral words were manipulated as expected, no expectation, and unexpected, based on these rules. This was followed by tasks focused on item and source memory. The study found that there was a "U-shape" relationship between expectation and item memory. Additionally, the study revealed the distinct impacts of expectation on item and source memory. When it came to item memory, both expected and unexpected words were better remembered than those with no expectations. In source memory, expected words showed memory inferiority for expectation-irrelevant source information, but an advantage for expectation-relevant source information. Stimulus emotionality modulated the effect of expectation on both item and source memory. Our findings provide behavioral evidence for the schema-linked interactions between medial prefrontal and medial temporal regions (SLIMM) theory, which proposes that congruent and incongruent events enhance memory through different brain regions. The different patterns between item and source memory also support dual-process models. Moreover, we speculate that processing events with varying levels of emotionality may undermine the impact of expectation, as implied by other neural investigations.

Valence precedes value in neural encoding of prediction error

Event-related potentials that follow feedback in reinforcement learning tasks have been proposed to reflect neural encoding of prediction errors. Prior research has shown that in the interval of 240-340 ms multiple different prediction error encodings appear to co-occur, including a value signal carrying signed quantitative prediction error and a valence signal merely carrying sign. The effects used to identify these two encoders, respectively a sign main effect and a sign × size interaction, do not reliably discriminate them. A full discrimination is made possible by comparing tasks in which the reinforcer available on a given trial is set to be either appetitive or aversive against tasks where a trial allows the possibility of either. This study presents a meta-analysis of reinforcement learning experiments, the majority of which presented the possibility of winning or losing money. Value and valence encodings were identified by conventional difference wave methodology but additionally by an analysis of their predicted behavior using a Bayesian analysis that incorporated nulls into the evidence for each encoder. The results suggest that a valence encoding, sensitive only to the available outcomes on the trial at hand precedes a later value encoding sensitive to the outcomes available in the wider experimental context. The implications of this for modeling computational processes of reinforcement learning in humans are discussed.

Cooperate or aggress? An opponent's tendency to cooperate modulates the neural dynamics of interpersonal cooperation

Humans are social animals and need to cooperate to survive. However, individuals are not cooperative in every social interaction, and their cooperation may depend on social context. The present study used a social dilemma game to investigate whether an opponent's tendency to be cooperative over time influenced a player's behavior and neural response to outcomes in the game. University students ("players") thought they were playing against other students ("opponents") in the Chicken Game but were actually playing against a programmed computer. Participants were randomly assigned to play with an opponent who tended to be competitive (cooperative 20% of the time) or who tended to be cooperative (cooperative 80% of the time). The results showed that early in the game, participants in both groups adopted a "tit-for-tat" strategy. However, as the game progressed and the opponent's behavioral tendency became more noticeable, players in the competitive-opponent group became generally more cooperative to limit their losses. ERPs analyses indicated that players had a higher P300 and larger theta power in response to the opponent's aggression but not to the opponent's cooperation when their opponent showed a tendency to be cooperative vs. competitive. The results suggest that people adjust their cooperative behavior based on their opponent's behavior in social interaction, and aggression captures more attention than cooperation in this process.

Social partner cooperativeness influences brain oxytocin transcription in Trinidadian guppies (Poecilia reticulata)

For non-kin cooperation to be maintained, individuals need to respond adaptively to the cooperative behaviour of their social partners. Currently, however, little is known about the biological responses of individuals to experiencing cooperation. Here, we quantify the neuroregulatory response of Trinidadian guppies (Poecilia reticulata) experiencing cooperation or defection by examining the transcriptional response of the oxytocin gene (oxt; also known as isotocin), which has been implicated in cooperative decision-making. We exposed wild-caught females to social environments where partners either cooperated or defected during predator inspection, or to a control (non-predator inspection) context, and quantified the relative transcription of the oxt gene. We tested an experimental group, originating from a site where individuals are under high predation threat and have previous experience of large aquatic predators (HP), and a control group, where individuals are under low predation threat and naïve to large aquatic predators (LP). LP, but not HP, fish showed different behavioural responses to the behaviour of their social environment, cooperating with cooperative partners and defecting when paired with defecting ones. In HP, but not LP, fish brain mid-section oxt relative transcription varied depending on social partner behaviour. HP fish experiencing cooperation during predator inspection had lower oxt transcription than those experiencing defection. This effect was not present in the control population or in the control context, where the behaviour of social partners did not affect oxt transcription. Our findings provide insight into the neuromodulation underpinning behavioural responses to social experiences, and ultimately to the proximate mechanisms underlying social decision-making.

Is there a self-positivity bias for destination memory? Behavioral and ERP evidence

Despite extensive existing research concerning source memory (i.e., memory for what has been said, given, or done to us by whom) during social interaction, destination memory (i.e., memory for what we have said, given, or done to whom) remains to be explored. Furthermore, although destination memory is believed to involve a self-reference process, it remains unclear whether such a process is sufficient to trigger a self-positivity bias. To address these issues, we combined the destination memory paradigm with the social dilemma game to compare destination memory for cooperation and cheating. Both behavioral performance and the neural index of successful encoding, the Dm (difference due to memory) effect, were concerned. Behaviorally, destination memory for cooperative, cheating, and neutral behaviors decreased successively. For neural activities, the pre-400 ms Dm effects during 200-400 ms were non-significant under any condition. In the latency windows of 400-800 ms and 800-1000 ms, the post-400 ms Dm effects were reliably observed for both cooperative and cheating behaviors and were statistically comparable between the two behavior types, but the effect was not obtained for neutral behaviors. These data suggest a self-positivity bias in the behavioral performance but not in the encoding-related Dm effects of destination memory.

Memory as a cognitive requirement for reciprocal cooperation

Memory has evolved to guide our decisions in the present and to prepare us for future interactions with the environment. Within the social domain, memory can help to decide with whom to cooperate. This provides a unique opportunity to study memory from a functional perspective. Although several lines of research have demonstrated that many forms of reciprocal cooperation require memory, most of the research does not support the assumption of a highly specialized cheater-detection module that specifically serves to promote the detection of uncooperative interaction partners. Instead, the literature supports the flexible recruitment of domain-general guessing and memory mechanisms that serve to continuously predict the future behavior of others based on situational and person-specific factors and use violations of these expectations to update the predictive models of who can be trusted to cooperate in reciprocal interactions.

Professional discrepancies of doctors and lawyers in episodic memory: Modulations of professional morality and warning

Past investigations have consistently demonstrated the robust stereotype-consistent effect in the circumstance of source memory but not always in item memory, including the case of professional stereotype. However, it remains unclear whether the effect still occurs in professional stereotype when considering the attributes of negative (or bad) or positive (or good); besides, it has not been concerned about how does warning work in remembering the professional stereotypical stimuli. The current experiments aimed to address these issues by adopting descriptive sentences as stimuli, which were related or unrelated to doctors and lawyers, and with different professional moral valences (negative, neutral, or positive). Item memory and source memory were tested successively. Experiment 1 without the explicit warning confirmed the reliable stereotype-consistent effect solely in source memory; the modulation of professional morality on memory behaved differently between doctor and lawyer, that is, negativity bias versus positivity bias. When giving an explicit warning (Experiment 2), the stereotype-consistent effect attenuated in the lawyer case, and the occurrence of negativity bias was sensitive to the memory task. Thus, our findings further reinforce the dual-process model; both professional morality and warning work in memory of professional stereotype, depending upon the nature of the profession, the concerned memory task, and also the presence of warning. Implications are made for future research to consider more perspectives.

Monetary payoffs modulate reciprocity expectations in outcome evaluations: An event-related potential study

Choosing cooperation or aggression relies on reciprocity preferences which refer to the tendency of an individual to return cooperative or aggressive action for cooperative or aggressive action (i.e., positive or negative reciprocity preference). The reciprocity preference is positively correlated with reciprocity expectation, wherein individuals with stronger reciprocity preferences may have higher expectations than future cooperative or aggressive behavior should be delivered by beneficiaries (positive reciprocity expectation) or victims (negative reciprocity expectation). Although previous studies have demonstrated that the presence of monetary payoffs enhances reciprocity preferences, the modulation of monetary payoffs in reciprocity expectations remains unclear. Using event-related potentials (ERPs), we examined how monetary payoffs modulated reciprocity expectations by adopting the Chicken game. Participants were asked to choose between cooperation and aggression with a putative opponent in the Chicken game involving the monetary (vs. non-monetary) payoffs. Participants' electroencephalogram (EEG) was recorded when they saw the opponent's cooperative or aggressive decision. Results showed that compared to the non-monetary payoff trials, the feedback-related negativity (FRN) effect in response to the opponent's decisions was stronger following the participant's aggressive decision in the monetary payoff trials, whereas P3 was insensitive to monetary payoffs. These findings suggest that monetary payoffs heighten expectations of negative reciprocity at the earlier and automatic outcome processing stage.

Neural processing of iterated prisoner's dilemma outcomes indicates next-round choice and speed to reciprocate cooperation

The iterated prisoner's dilemma (iPD) game is a well-established model for testing how people cooperate, and the neural processes that unfold after its distinct outcomes have been partly described. Recent theoretical models suggest evolution favors intuitive cooperation, which raises questions on the behavioral but also neural timelines involved. We studied the outcome/feedback stage of iPD rounds with electroencephalography (EEG) methods. Results showed that neural signals associated with this stage also relate to future choice, in an outcome-dependent manner: (i) after zero-gain "sucker's payoffs" (unreciprocated cooperation), a participant's decision thereafter relates to changes to the feedback-related negativity (FRN); (ii) after one-sided non-cooperation (participant wins at co-player's expense), by the P3; (iii) after mutual cooperation, by late frontal delta-band modulations. Critically, faster reciprocation behavior towards a co-player's choice to cooperate was predicted, on a single-trial basis, by players' P3 and frontal delta modulations at the immediately preceding trial. Delta-band signaling is discussed in relation to homeostatic regulation processing in the literature. The findings relate the early outcome/feedback stage to subsequent decisional processes in the iPD, providing a first neural account of the brief timelines implied in heuristic modes of cooperation.

Trinidadian guppies use a social heuristic that can support cooperation among non-kin

Cooperation among non-kin is well documented in humans and widespread in non-human animals, but explaining the occurrence of cooperation in the absence of inclusive fitness benefits has proven a significant challenge. Current theoretical explanations converge on a single point: cooperators can prevail when they cluster in social space. However, we know very little about the real-world mechanisms that drive such clustering, particularly in systems where cognitive limitations make it unlikely that mechanisms such as score keeping and reputation are at play. Here, we show that Trinidadian guppies (Poecilia reticulata) use a 'walk away' strategy, a simple social heuristic by which assortment by cooperativeness can come about among mobile agents. Guppies cooperate during predator inspection and we found that when experiencing defection in this context, individuals prefer to move to a new social environment, despite having no prior information about this new social group. Our results provide evidence in non-human animals that individuals use a simple social partner updating strategy in response to defection, supporting theoretical work applying heuristics to understanding the proximate mechanisms underpinning the evolution of cooperation among non-kin.

Higher Status Honesty Is Worth More: The Effect of Social Status on Honesty Evaluation

Promises are crucial for maintaining trust in social hierarchies. It is well known that not all promises are kept; yet the effect of social status on responses to promises being kept or broken is far from understood, as are the neural processes underlying this effect. Here we manipulated participants' social status before measuring their investment behavior as Investor in iterated Trust Game (TG). Participants decided how much to invest in their partners, who acted as Trustees in TG, after being informed that their partners of higher or lower social status either promised to return half of the multiplied sum (4 × invested amount), did not promise, or had no opportunity to promise. Event-related potentials (ERPs) were recorded when the participants saw the Trustees' decisions in which the partners always returned half of the time, regardless of the experimental conditions. Trustee decisions to return or not after promising to do so were defined as honesty and dishonesty, respectively. Behaviorally, participants invested more when Trustees promised than when Trustees had no opportunity to promise, and this effect was greater for higher status than lower status Trustees. Neurally, when viewing Trustees' return decisions, participants' medial frontal negativity (MFN) responses (250-310 ms post onset) were more negative when Trustees did not return than when they did return, suggesting that not returning was an expectancy violation. P300 responses were only sensitive to higher status return feedback, and were more positive-going for higher status partner returns than for lower status partner returns, suggesting that higher status returns may have been more rewarding/motivationally significant. Importantly, only participants in low subjective socioeconomic status (SES) evidenced an increased P300 effect for higher status than lower status honesty (honesty - dishonesty), suggesting that higher status honesty was especially rewarding/motivationally significant for participants with low SES. Taken together, our results suggest that in an earlier time window, MFN encodes return valence, regardless of honesty or social status, which are addressed in a later cognitive appraisal process (P300). Our findings suggest that social status influences honesty perception at both a behavioral and neural level, and that subjective SES may modulate this effect.

Separating conditional and unconditional cooperation in a sequential Prisoner's Dilemma game

Most theories of social exchange distinguish between two different types of cooperation, depending on whether or not cooperation occurs conditional upon the partner’s previous behaviors. Here, we used a multinomial processing tree model to distinguish between positive and negative reciprocity and cooperation bias in a sequential Prisoner’s Dilemma game. In Experiments 1 and 2, the facial expressions of the partners were varied to manipulate cooperation bias. In Experiment 3, an extinction instruction was used to manipulate reciprocity. The results confirm that people show a stronger cooperation bias when interacting with smiling compared to angry-looking partners, supporting the notion that a smiling facial expression in comparison to an angry facial expression helps to construe a situation as cooperative rather than competitive. Reciprocity was enhanced for appearance-incongruent behaviors, but only when participants were encouraged to form expectations about the partners’ future behaviors. Negative reciprocity was not stronger than positive reciprocity, regardless of whether expectations were manipulated or not. Experiment 3 suggests that people are able to ignore previous episodes of cheating as well as previous episodes of cooperation if these turn out to be irrelevant for predicting a partner’s future behavior. The results provide important insights into the mechanisms of social cooperation.

Who Deserves My Trust? Cue-Elicited Feedback Negativity Tracks Reputation Learning in Repeated Social Interactions

Trust and trustworthiness contribute to reciprocal behavior and social relationship development. To make better decisions, people need to evaluate others’ trustworthiness. They often assess this kind of reputation by learning through repeated social interactions. The present event-related potential (ERP) study explored the reputation learning process in a repeated trust game where subjects made multi-round decisions of investment to different partners. We found that subjects gradually learned to discriminate trustworthy partners from untrustworthy ones based on how often their partners reciprocated the investment, which was indicated by their own investment decisions. Besides, electrophysiological data showed that the faces of the untrustworthy partners induced larger feedback negativity (FN) amplitude than those of the trustworthy partners, but only in the late phase of the game. The ERP results corresponded with the behavioral pattern and revealed that the learned trustworthiness differentiation was coded by the cue-elicited FN component. Consistent with previous research, our findings suggest that the anterior cue-elicited FN reflects the reputation appraisal and tracks the reputation learning process in social interactions.

Facial Likability and Smiling Enhance Cooperation, but Have No Direct Effect on Moralistic Punishment

The present study serves to test how positive and negative appearance-based expectations affect cooperation and punishment. Participants played a prisoner's dilemma game with partners who either cooperated or defected. Then they were given a costly punishment option: They could spend money to decrease the payoffs of their partners. Aggregated over trials, participants spent more money for punishing the defection of likable-looking and smiling partners compared to punishing the defection of unlikable-looking and nonsmiling partners, but only because participants were more likely to cooperate with likable-looking and smiling partners, which provided the participants with more opportunities for moralistic punishment. When expressed as a conditional probability, moralistic punishment did not differ as a function of the partners' facial likability. Smiling had no effect on the probability of moralistic punishment, but punishment was milder for smiling in comparison to nonsmiling partners.

How Negative Social Bias Affects Memory for Faces: An Electrical Neuroimaging Study

During social interactions, we make inferences about people’s personal characteristics based on their appearance. These inferences form a potential prejudice that can positively or negatively bias our interaction with them. Not much is known about the effects of negative bias on face perception and the ability to recognize people faces. This ability was investigated by recording event-related potentials (ERPs) from 128 sites in 16 volunteers. In the first session (encoding), they viewed 200 faces associated with a short fictional story that described anecdotal positive or negative characteristics about each person. In the second session (recognition), they underwent an old/new memory test, in which they had to distinguish 100 new faces from the previously shown faces. ERP data relative to the encoding phase showed a larger anterior negativity in response to negatively (vs. positively) biased faces, indicating an additional processing of faces with unpleasant social traits. In the recognition task, ERPs recorded in response to new faces elicited a larger FN400 than to old faces, and to positive than negative faces. Additionally, old faces elicited a larger Old-New parietal response than new faces, in the form of an enlarged late positive (LPC) component. An inverse solution SwLORETA (450–550 ms) indicated that remembering old faces was associated with the activation of right superior frontal gyrus (SFG), left medial temporal gyrus, and right fusiform gyrus. Only negatively connoted faces strongly activated the limbic and parahippocampal areas and the left SFG. A dissociation was found between familiarity (modulated by negative bias) and recollection (distinguishing old from new faces).

The implicit cognition of reciprocal exchange: automatic retrieval of positive and negative experiences with partners in a prisoner's dilemma game

Models of reciprocity imply that cheater detection is an important prerequisite for successful social exchange. Considering the fundamental role of memory in reciprocal exchange, these theories lead to the prediction that memory for cheaters should be preferentially enhanced. Here, we examine whether information of a partner's previous behaviour in an interaction is automatically retrieved when encountering the face of a partner who previously cheated or cooperated. In two studies, participants played a sequential prisoner's dilemma game with cheaters and cooperative partners. Alternating with the game blocks, participants were asked to classify the smiling or angry facial expressions of cooperators and cheaters. Both experiments revealed congruence effects, reflecting faster identification of the smiles of cooperators (Experiments 1 and 2) and faster identification of the angry facial expressions of cheaters (Experiment 2). Our study provides evidence for the automatic retrieval of the partner's behaviour in the game, regardless of whether partners cheated or cooperated, and thus provides further evidence against the cheater detection hypothesis.