Name: the joint effect of social comparison and social distance on evaluation of intertemporal choice outcomes in event-related potential studies
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This work was supported by the project of National Natural Science Foundation of China (72001055), the project of Social Science Foundation of Heilongjiang Province of China (18JLC219), the project of Postdoctoral Foundation of Heilongjiang Province of China (LBH-Z18018), the project of Scholars Plan of Northeast Agricultural University (2019), and the Philosophy and Social Science Research Project of Jiangsu Provincial Department of Education (2018SJA1089).
We thank all colleagues in Lab 412, especially Zhikai Song and Xinyue Jia, for their assistance in the experiment. We would also like to thank the editors and anonymous reviewers for their valuable suggestions.

This research scheme was approved by the local and institutional ethics committee and complies with the latest version of the Declaration of Helsinki. All participants provided written informed consent before participating. The participants had normal vision or normal correction and no psychiatric or neurological disorders. The participants did not have drug or psychotropic medication using experience and no perm or hair dyeing history within six months. If subjects had excessive artifacts in the EEG data, they were not ...

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Experimental results and significance 
Generally, additional tasks, such as social distance perception and social comparison, compete for cognitive resources with the intertemporal decision-making task at different cognitive stages. Firstly, both social distance and time delay have main effects on N100 amplitude, respectively. The present results indicate that gambling with friends induces a greater N100 amplitude than with strangers. Moreover, immediate outcomes elicit greater N100 amplitude than d...

In daily life, people often face the choice of enjoying the present or investing in the future. This decision, known as intertemporal choice, requires individuals to weigh the value of outcomes at different time points1,2,3. Over time, the subjective evaluation of outcomes declines hyperbolically or quasi-hyperbolically4,5,6,7. People tend to prefer small-but-immediate gains over larger-but-later ones8.
Previous research has examined various factors influencing intertemporal decision-making. For instance, D. Wang et al.9 explored self-other differences in intertemporal decision-making and found that decisions made for oneself or friends tend to prefer delayed larger rewards over immediate smaller rewards compared to decisions made for strangers. The closeness of social relationships affects individuals&#39; perception of time, thereby impacting their intertemporal decision-making. Similarly, Zhao et al.10 conducted experiments on self-other decision-making in time-based intertemporal choice. The results revealed that participants tend to opt for the smaller immediate option when making decisions for others, but they prefer the large-but-later option for themselves, highlighting the influence of personal interests on the intertemporal decision-making process.
While previous studies have focused on the behavioral and psychological aspects of intertemporal decision-making, they have not provided a direct understanding of the cognitive process or an in-depth analysis of the underlying neural mechanisms. However, an increasing number of recent studies have employed the event-related potentials (ERPs) method to explore intertemporal decision-making and its neurocognitive processes. ERPs refer to the measured brain responses resulting from specific sensory, cognitive, or motor events11. The use of ERPs offers two significant advantages for studying intertemporal decision-making. Firstly, its high temporal resolution enables the differentiation of the temporal sequence of different cognitive processes. Secondly, ERPs components can serve as indicators of specific cognitive processes. For instance, H. Y. Zhang et al.12 utilized ERPs to investigate the effect of social distance on outcome comparison between individuals and their partners. They concluded that personal closeness moderates individuals&#39; subjective sensitivity during the outcome comparison phase. The study also found that participants expressed greater satisfaction with the loss outcomes of dislikeable players. ERPs components were employed to analyze influential cognitive processes, showing that this higher satisfaction with loss outcomes for dislikeable players resulted from subjects&#39; increased sensitivity to evaluative, motivational, and emotional processes involved in social comparison.
Previous studies have primarily focused on the competition for cognitive resources between immediate and delayed options in intertemporal decision-making. However, the brain simultaneously processes various tasks, including social comparison and social distance, which further competes for limited cognitive resources. As a result, fewer cognitive resources are allocated to the intertemporal decision-making task. To accurately investigate the influence of external factors on intertemporal decision outcomes, it is crucial to identify the equilibrium state of cognitive resource allocation between immediate and delayed outcome evaluation. In the equilibrium state, individuals assign the same subjective value to the delayed outcome as they do to the immediate outcome. However, if external factors, such as social comparison and social distance, are given more weight in the equilibrium state, it disrupts the cognitive resource balance in intertemporal decision-making. As a result, the cognitive difference between the equilibrium and inequilibrium state can precisely reflect the impact of external factors on the evaluation of intertemporal decision results. The &#34;indifference point&#34; represents the balance point of the delayed outcome on a fixed date in the future, equivalent to the subjective value of the immediate outcome13. Some existing studies on intertemporal decision-making have not set the indifference point for each participant in their experimental paradigm. Instead, they calculate the subject&#39;s time discount rate in advance using a delay discount task (DDT) and categorize participants into high and low time discount rate groups. Consequently, the results of studies exploring external factors influencing intertemporal decision-making become inconsistent due to the imbalanced allocation of cognitive resources between immediate and delayed option evaluation14,15,16.
Only a limited number of studies have explored the combined influence of social comparison and social distance on individuals&#39; intertemporal decision-making, and even fewer have utilized the ERPs technique. Consequently, the underlying neural mechanism of intertemporal choice outcome evaluation in the presence of both social factors remains unclear. Existing studies on the impact of external factors on intertemporal decision-making have suffered from inadequate setting of indifference points for delayed outcomes, leading to potential deviations in measuring the effect of these external factors. Different individuals may assign different subjective value evaluations to the same amount of rewards, necessitating the setting of individualized indifference points for each participant to eliminate interference caused by inequitable cognitive resource allocation during intertemporal outcome evaluation. A new experimental paradigm, in which the indifference point for delayed outcomes is determined in advance, is essential to address this issue. A previous study proposed such a paradigm with a fixed one-month delay outcome indifference point, yielding results consistent with expectations from cognitive resource competition theory17. Though setting an indifference point in advance may introduce bias, it can still effectively influence participants through psychological cues and cognitive reinforcement.
In contrast to prior research where participants merely observed intertemporal choices without direct personal involvement, the current study presents a novel experimental paradigm. Participants are not only engaged in the gambling task but also required to compare their outcomes with others who transition from being strangers to friends. This paradigm explores both individual self-interest in intertemporal choices and the cognitive processing of social comparison, significantly differing from previous investigations. By having participants report their indifference points for one-month delayed outcomes in the DDT task and subsequently using these self-reported indifference points as the delay option&#39;s outcome in the upcoming intertemporal decision-making task, this study aims to provide a pure measurement of the joint influence of social comparison and social distance on outcome evaluation in intertemporal decision-making, assuming no glitches occur during the indifference point setting process.
People not only need to perceive interpersonal relationships but also engage in social comparison by comparing their outcomes with others. However, it is unclear whether the interpersonal perceptual task and the social comparison task consume cognitive resources independently or compete for resources during the integrated assessment of the time value of intertemporal choice outcomes. The N100 is a negative deflected brain wave occurring within a 100 ms time window after an event, considered an indicator of attention distribution before comprehensive outcome evaluation. Its amplitude decreases as the number of attention resources increases18. Liu et al.19 found a significant effect of social distance during the early N100 stage of outcome processing, suggesting that individuals tend to compare themselves with close people on the ability dimension during the primary stage of outcome processing. Additionally, Mason et al.20 argued that subjects exhibited more negative N100 amplitudes in response to immediate rewards compared to delayed rewards, indicating that temporal delay is encoded in early neural processing.
The P300 is a positive deflected brain wave appearing around 300 ms after an event, serving as a direct index of outcome evaluation. A larger P300 amplitude indicates a higher attentional allocation and more exhaustive outcome assessment12. H. Y. Zhang et al.12 demonstrated that the P300 was larger during the outcome evaluation phase of gambling with dislikeable players, reflecting participants&#39; stronger motivation to outperform dislikeable players. Moreover, anxious individuals may struggle with concentrating or focusing on anything beyond their present worries due to their avoidance of future uncertainties21. An ERP study on the influence of anxiety levels on intertemporal choice outcomes showed that highly anxious individuals exhibited a significantly more positive P300 amplitude when seeing the immediate option compared to the delayed option22. According to resource allocation theory, cognitive resources allocated to the intertemporal decision-making task are reduced during the comprehensive outcome assessment phase. Hypothesis 1 proposes competition for cognitive resources between the interpersonal perceptual task, social comparison task, and intertemporal decision-making task at different cognitive stages. At the electrophysiological level, there are main or interaction effects for social distance and time delay on the N100 component, and for social comparison and time delay on the P300 component.
Based on cognitive resource competition theory, when additional tasks such as social comparison and interpersonal perceptual tasks are introduced, they compete for limited cognitive resources with the intertemporal decision-making task. As a result, fewer cognitive resources are available for the intertemporal decision-making task, leading to a lack of elaborate processing of the time effect on outcome evaluation. This results in individuals having a reduced sensitivity to time and a smaller time discounting rate. In light of this theory, hypothesis 2 is proposed for the present study: when participants face both social comparison and interpersonal perceptual tasks simultaneously, they will have a higher evaluation for delayed outcomes. Specifically, compared to immediate rewards, delayed rewards will elicit a more positive P300 amplitude at the EEG level. This effect is expected due to the increased competition for cognitive resources, leading to a stronger attentional allocation and more exhaustive evaluation of delayed outcomes.
According to D. Kahneman23, attention is divisible, and the allocation of attention is a matter of degree. When faced with multiple parallel tasks, individuals prioritize them based on their relevance to self-interest and allocate cognitive resources accordingly24. However, numerous studies have indicated that an inferior task with limited cognitive resources may be susceptible to interference and have negligible effects on other tasks. This could be due to a significant disparity in cognitive resource allocation between tasks of different priorities. In the present experimental paradigm, the intertemporal decision-making task is considered a superior task directly linked to self-interest, thus receiving the highest priority in cognitive resource allocation. Compared to the social comparison task and the interpersonal perceptual task, the intertemporal decision-making task is allocated cognitive resources at least one order of magnitude higher. Hypothesis 3 proposes that despite the simultaneous processing of the social comparison task and the interpersonal perceptual task, individuals will rate the immediate and delayed outcomes equally. This means that there will be no significant difference in the P300 component of neural activities between immediate and delayed outcome conditions. This hypothesis is based on the premise that the intertemporal decision-making task receives significantly more cognitive resources due to its higher priority, making the cognitive resource competition between immediate and delayed outcomes less pronounced. As a result, individuals would evaluate the two outcomes equally at the neural activity level.
When individuals perceive that their reward is less than what others receive, they often experience feelings of dissatisfaction and anger. This realization can motivate them to either seek changes in the current situation or withdraw from comparisons altogether to establish a perceived sense of fairness25. In an unfairly disadvantaged circumstance, a significant disparity in rewards can negatively impact an individual&#39;s self-esteem, leading them to avoid comparing themselves with others and redirecting cognitive resources to a less challenging task26. As a psychological defense mechanism, individuals facing an unfair disadvantage comparison condition will reallocate cognitive resources from the social comparison task to the intertemporal decision-making task. Higher time discounting rates are associated with greater cognitive resource allocation. Based on the above understanding, the present article proposes hypothesis 4: in comparison to both fair or unfair advantage conditions, subjects will assign lower evaluations to delayed rewards in the unfair disadvantage condition. At the electrophysiological level, this is expected to be reflected in a smaller P300 component elicited by delayed rewards in the unfair disadvantaged condition. This effect occurs due to the reallocation of cognitive resources to the intertemporal decision-making task, leading to reduced attentional allocation and a less exhaustive evaluation of delayed outcomes.
In the context of the unfairly disadvantaged circumstance, the reallocation of increased cognitive resources to the intertemporal decision-making task may not significantly impact the assessment of immediate outcomes. This is because the immediate outcome&#39;s time value may not require extensive processing, leading to a lesser influence of cognitive resource reallocation on this aspect. Therefore, hypothesis 5 is proposed, suggesting that in the unfairly disadvantaged circumstance, people are more likely to opt for an immediate reward. At the neural activity level, there will be a distinct difference in the P300 component between the immediate and delayed outcomes due to the different sensitivity of time perception.
Additionally, when individuals are engaged in a gambling task with a friend and face an unfair outcome, fewer cognitive resources will be allocated to the evaluation of the intertemporal choice&#39;s outcome due to the demands of perceiving and processing social relationships. Consequently, as a result of reduced cognitive resources, individuals become less sensitive to time in this situation. Hence, hypothesis 6 is raised: compared to interactions with strangers, people will express more satisfaction with delayed rewards in the unfairly disadvantaged condition. This means that delayed rewards will produce a larger P300 component at the neural activity level in the context of interactions with friends compared to strangers.

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			<td>Electrode caps&#160;</td>
			<td>Neurosoft Labs, Inc, USA</td>
			<td>64 Ag/AgCl electrodes</td>
			<td>&#160;with a configuration of the international 10&#8211;20 system of electrode</td>
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			<td>E-Prime software</td>
			<td>Psychology Software Tools, Inc, USA</td>
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			<td>ROYAL PHILIPS, Netherlands</td>
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			<td>NeuroScan Synamp2 Amplifier</td>
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the joint effect of social comparison and social distance on evaluation of intertemporal choice outcomes in event-related potential studies

Intertemporal choice plays a crucial role in our daily lives, influencing decisions related to education, health, consumption, and investment. This research proposes an innovative experimental protocol that examines how social comparison and social distance jointly affect the neural processes involved in outcome assessment for intertemporal choices. The study is based on the theoretical framework of cognitive resource competition. This protocol enables researchers to dynamically establish an indifference point for each participant, effectively eliminating the influence of any biased indifference points on the assessment of intertemporal choices. Consequently, the study solely measures the combined impact of social comparison and social distance on how participants evaluate intertemporal choice outcomes. The findings reveal that individuals are more inclined to opt for immediate outcomes under negative unfair conditions. Moreover, compared to the fair and positive unfair conditions, people tend to undervalue delayed outcomes in the negative unfair condition. The strength of this approach lies in its dynamic indifference point setting, making it an effective method to investigate the influence of various external factors (such as social status and power level) on intertemporal decision-making. While the protocol is designed to measure electrophysiological events like event-related potentials, it can also be tailored for use with fMRI.

IOS scale result 
The IOS scale score30 was used to examine the social distance and self-relevance of the participants to friends and strangers, and it was found that the social distance of the participants to friends (6.20 &#177; 0.696) was higher than the social distance of the participants to strangers (1.45 &#177; 0.605), t(19) = 21.978, p &#60; 0.001, 95%, Cl = (4.30 - 5.20), revealing that the social distance manipulation is effective.
<p class="jove_conten...

Watch this Scientific Journal Video about The Joint Effect of Social Comparison and Social Distance on Evaluation of Intertemporal Choice Outcomes in Event-related Potential Studies at JoVE.com

The Joint Effect of Social Comparison and Social Distance on Evaluation of Intertemporal Choice Outcomes in Event-related Potential Studies

This protocol aims to investigate the neural activity related to social comparison and social distance during the processing of intertemporal decision outcomes. Indifference points will be measured using event-related potentials as part of the study.

Intertemporal choice plays a crucial role in our daily lives, influencing decisions related to education, health, consumption, and investment. This ...

This protocol enables researchers to dynamically establish an indifference point for each participant, effectively eliminating the influence of any biased indifference points on the assessment of inter-temporal choices. The event related potential or ERP techniques, high-temporal resolution enables the differentiation of the temporal sequence of different cognitive processes. Additionally, ERP components can serve as indicators of specific cognitive processes.Begin by making the participant perform the delayed discounting task or DDT as the first stage task to measure the participant's indifference points. To do so, give the participant two paper cards to choose from, one of which indicates a fixed amount of 10 or 20 China Yuan that the participant will obtain immediately. And the other card shows a variable amount of money that will be obtained after one month.Let the participant continue to the next trial if he or she chooses the immediate reward. After each trial, change the variable amount card to set the next pair of cards before asking the participant to make a new choice. Starting from 10 or 20 China Yuan, increase the variable amount by one China Yuan for each trial, up to 25 or 35 China Yuan, respectively.End the experiment when the participant chooses a delayed reward card. Consider that card amount as the participant's indifference point. After the first stage task, proceed to make the participant perform a gambling task in the second stage of the event related potential task.Begin the task by displaying the fixation at the center of the screen for a random duration of 400 to 600 milliseconds. Then display the opponent's name for 1000 milliseconds before presenting two cards symmetrically on both sides of the fixation at the center of the cue interface screen. Ask the player to choose either the left card by pressing one on an external numeric keypad or the right card by pressing three on the keypad.Ensure the selected card is highlighted with a red rim for 1000 milliseconds after the participant decides. Display the outcomes of both the participant and the opponent for 1000 milliseconds. Finally, display a blank screen for 500 milliseconds.Ask only one from the participant pair to make a response to the task and wear the electrode cap. Instruct participants to enter the experimental room and sit in a comfortable chair about one meter from the screen. Next, have them perform the DDT task as demonstrated previously to record the indifference points of the participant.After the DDT task, use the alcohol and facial scrub one after the other to gently scrub the skin on the participant's face. To position the electrode cap with the 64 silver silver chloride electrodes on the participant's head, first, place the CZ electrode at the top of the head and then confirm the position of the cap. Then, place the corresponding electrodes on the tip of the participant's nose.Place the reference electrodes about 10 millimeters above and below the left eye, near the other canthus of both sides, and on the left and right mastoids. After filling the conductive gel, tighten the external electrodes with an adhesive bandage. Moderately tighten the electrode cap strap on the chin to prevent the electrodes from shifting during the experiment.Next, using a blunt tipped syringe, fill the internal cylindrical space of all electrodes in the cap with conductive gel. Observe the real-time impedance value on the display until the impedance falls below the desired threshold of 10 kilo ohms. Prior to the beginning of the experiment, display a guide on the screen to familiarize the participants with the procedures and appropriate responses.Implement the formal experiment session using 480 trials and record the corresponding electroencephalogram or EEG signals of the participant. Divide the trials into six blocks, allowing the participants to take a two-minute break between blocks. After saving the recorded EEG data, assist the participants with removing the electrode cap and help them wash the conductive gel residue from their hair or skin.A two by four set of gambles were designed based on time delay and social comparison, which was further factored with two social distance parameters. The waveform diagram and topographic map of the brain for the N100 component showed significant main effects of social distance and time delay. Friends caused more negative N100 amplitude than strangers and immediate outcome conditions caused more negative N100 amplitude than delayed outcome conditions.The waveform diagram and topographic map of the P300 components showed the main effects of social comparison. The results of post pairwise comparison revealed that the better outcome of the positive unfair, and equal outcome of the large fair were more positive than the worse outcome of negative unfair. The social comparison coupled with time delay interaction was significant at the 0.1 level.When the result was a worse outcome of the negative unfair condition, the P300 caused by the immediate gain was greater than the delayed gain. When the outcome was delayed, the P300 components of small fair condition, positive unfair condition, and large fair condition, although not significantly different, were more positive than the worse outcome of negative unfair. The assessment of the indifference point for the participant is crucial, and the value must be recorded accurately and applied in the subsequent experimental steps.This protocol can be adopted to further explore the functional integration and separation involving different times and different brain regions in the field of inter-temporal decision making by means of FMRI. This protocol not only investigates the joint effect of social comparison and social distance, but also studies the influence of other external factors on the evaluation of inter-temporal choice outcomes.

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Research

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Neuroscience

High Density Event-related Potential  Data Acquisition in Cognitive Neuroscience

Functional magnetic resonance imaging (fMRI) is currently the standard method of evaluating brain function in the field of Cognitive Neuroscience, in part because fMRI data acquisition and analysis techniques are readily available. Because fMRI has excellent spatial resolution but poor temporal resolution, this method can only be used to identify the spatial location of brain activity associated with a given cognitive process (and reveals virtually nothing about the time course of brain activity). By contrast, event-related potential (ERP) recording, a method that is used much less frequently than fMRI, has excellent temporal resolution and thus can track rapid temporal modulations in neural activity. Unfortunately, ERPs are under utilized in Cognitive Neuroscience because data acquisition techniques are not readily available and low density ERP recording has poor spatial resolution. In an effort to foster the increased use of ERPs in Cognitive Neuroscience, the present article details key techniques involved in high density ERP data acquisition. Critically, high density ERPs offer the promise of excellent temporal resolution and good spatial resolution (or excellent spatial resolution if coupled with fMRI), which is necessary to capture the spatial-temporal dynamics of human brain function.

Event-related potential (ERP) recording is under utilized in Cognitive Neuroscience because data acquisition techniques are not readily available and this method often has poor spatial resolution. To foster the increased use of ERPs in Cognitive Neuroscience, the present article details key techniques involved in high density ERP data acquisition.

Functional magnetic resonance imaging (fMRI) is currently the standard method of evaluating brain function in the field of Cognitive Neuroscience, in part ...

Combining Behavioral Endocrinology and Experimental Economics: Testosterone and Social Decision Making

Behavioral endocrinological research in humans as well as in animals suggests that testosterone plays a key role in social interactions. Studies in rodents have shown a direct link between testosterone and aggressive behavior1 and folk wisdom adapts these findings to humans, suggesting that testosterone induces antisocial, egoistic or even aggressive behavior2. However, many researchers doubt a direct testosterone-aggression link in humans, arguing instead that testosterone is primarily involved in status-related behavior3,4. As a high status can also be achieved by aggressive and antisocial means it can be difficult to distinguish between anti-social and status seeking behavior.
We therefore set up an experimental environment, in which status can only be achieved by prosocial means. In a double-blind and placebo-controlled experiment, we administered a single sublingual dose of 0.5 mg of testosterone (with a hydroxypropyl-&beta;-cyclodextrin carrier) to 121 women and investigated their social interaction behavior in an economic bargaining paradigm. Real monetary incentives are at stake in this paradigm; every player A receives a certain amount of money and has to make an offer to another player B on how to share the money. If B accepts, she gets what was offered and player A keeps the rest. If B refuses the offer, nobody gets anything. A status seeking player A is expected to avoid being rejected by behaving in a prosocial way, i.e. by making higher offers.
The results show that if expectations about the hormone are controlled for, testosterone administration leads to a significant increase in fair bargaining offers compared to placebo. The role of expectations is reflected in the fact that subjects who report that they believe to have received testosterone make lower offers than those who say they believe that they were treated with a placebo. These findings suggest that the experimental economics approach is sensitive for detecting neurobiological effects as subtle as those achieved by administration of hormones. Moreover, the findings point towards the importance of both psychosocial as well as neuroendocrine factors in determining the influence of testosterone on human social behavior.

The procedure described in this protocol shows that testosterone administration and folk beliefs about testosterone may be associated with directly opposed social behaviors.

Behavioral endocrinological research in humans as well as in animals suggests that testosterone plays a key role in social interactions. Studies in ...

Combining Computer Game-Based Behavioural Experiments With High-Density EEG and Infrared Gaze Tracking

Experimental paradigms are valuable insofar as the timing and other parameters of their stimuli are well specified and controlled, and insofar as they yield data relevant to the cognitive processing that occurs under ecologically valid conditions. These two goals often are at odds, since well controlled stimuli often are too repetitive to sustain subjects' motivation. Studies employing electroencephalography (EEG) are often especially sensitive to this dilemma between ecological validity and experimental control: attaining sufficient signal-to-noise in physiological averages demands large numbers of repeated trials within lengthy recording sessions, limiting the subject pool to individuals with the ability and patience to perform a set task over and over again. This constraint severely limits researchers' ability to investigate younger populations as well as clinical populations associated with heightened anxiety or attentional abnormalities. Even adult, non-clinical subjects may not be able to achieve their typical levels of performance or cognitive engagement: an unmotivated subject for whom an experimental task is little more than a chore is not the same, behaviourally, cognitively, or neurally, as a subject who is intrinsically motivated and engaged with the task. A growing body of literature demonstrates that embedding experiments within video games may provide a way between the horns of this dilemma between experimental control and ecological validity. The narrative of a game provides a more realistic context in which tasks occur, enhancing their ecological validity (Chaytor &amp; Schmitter-Edgecombe, 2003). Moreover, this context provides motivation to complete tasks. In our game, subjects perform various missions to collect resources, fend off pirates, intercept communications or facilitate diplomatic relations. In so doing, they also perform an array of cognitive tasks, including a Posner attention-shifting paradigm (Posner, 1980), a go/no-go test of motor inhibition, a psychophysical motion coherence threshold task, the Embedded Figures Test (Witkin, 1950, 1954) and a theory-of-mind (Wimmer &amp; Perner, 1983) task. The game software automatically registers game stimuli and subjects' actions and responses in a log file, and sends event codes to synchronise with physiological data recorders. Thus the game can be combined with physiological measures such as EEG or fMRI, and with moment-to-moment tracking of gaze. Gaze tracking can verify subjects' compliance with behavioural tasks (e.g. fixation) and overt attention to experimental stimuli, and also physiological arousal as reflected in pupil dilation (Bradley et al., 2008). At great enough sampling frequencies, gaze tracking may also help assess covert attention as reflected in microsaccades - eye movements that are too small to foveate a new object, but are as rapid in onset and have the same relationship between angular distance and peak velocity as do saccades that traverse greater distances. The distribution of directions of microsaccades correlates with the (otherwise) covert direction of attention (Hafed &amp; Clark, 2002).

Procedures for recording high-density EEG and gaze data during computer game-based cognitive tasks are described. Using a video game to present cognitive tasks enhances ecological validity without sacrificing experimental control.

Experimental paradigms are valuable insofar as the timing and other parameters of their stimuli are well specified and controlled, and insofar as they ...

Brain Imaging Investigation of the Neural Correlates of Observing Virtual Social Interactions

The ability to gauge social interactions is crucial in the assessment of others&#x2019; intentions. Factors such as facial expressions and body language affect our decisions in personal and professional life alike 1. These "friend or foe" judgements are often based on first impressions, which in turn may affect our decisions to "approach or avoid". Previous studies investigating the neural correlates of social cognition tended to use static facial stimuli 2. Here, we illustrate an experimental design in which whole-body animated characters were used in conjunction with functional magnetic resonance imaging (fMRI) recordings. Fifteen participants were presented with short movie-clips of guest-host interactions in a business setting, while fMRI data were recorded; at the end of each movie, participants also provided ratings of the host behaviour. This design mimics more closely real-life situations, and hence may contribute to better understanding of the neural mechanisms of social interactions in healthy behaviour, and to gaining insight into possible causes of deficits in social behaviour in such clinical conditions as social anxiety and autism 3.

This article demonstrates an experimental design in which whole-body animated characters are used in conjunction with functional magnetic resonance imaging (fMRI) to investigate the neural correlates of observing virtual social interactions.

The ability to gauge social interactions is crucial in the assessment of others&#x2019; intentions. Factors such as facial expressions and body language ...

Assessment of Social Interaction Behaviors

Social interactions are a fundamental and adaptive component of the biology of numerous species. Social recognition is critical for the structure and stability of the networks and relationships that define societies. For animals, such as mice, recognition of conspecifics may be important for maintaining social hierarchy and for mate choice 1.
A variety of neuropsychiatric disorders are characterized by disruptions in social behavior and social recognition, including depression, autism spectrum disorders, bipolar disorders, obsessive-compulsive disorders, and schizophrenia. Studies of humans as well as animal models (e.g., Drosophila melanogaster, Caenorhabditis elegans, Mus musculus, Rattus norvegicus) have identified genes involved in the regulation of social behavior 2. To assess sociability in animal models, several behavioral tests have been developed (reviewed in 3). Integrative research using animal models and appropriate tests for social behavior may lead to the development of improved treatments for social psychopathologies.
The three-chamber paradigm test known as Crawley's sociability and preference for social novelty protocol has been successfully employed to study social affiliation and social memory in several inbred and mutant mouse lines (e.g. 4-7). The main principle of this test is based on the free choice by a subject mouse to spend time in any of three box's compartments during two experimental sessions, including indirect contact with one or two mice with which it is unfamiliar. To quantitate social tendencies of the experimental mouse, the main tasks are to measure a) the time spent with a novel conspecific and b) preference for a novel vs. a familiar conspecific. Thus, the experimental design of this test allows evaluation of two critical but distinguishable aspects of social behavior, such as social affiliation/motivation, as well as social memory and novelty. "Sociability" in this case is defined as propensity to spend time with another mouse, as compared to time spent alone in an identical but empty chamber 7. "Preference for social novelty" is defined as propensity to spend time with a previously unencountered mouse rather than with a familiar mouse 7. This test provides robust results, which then must be carefully analyzed, interpreted and supported/confirmed by alternative sociability tests. In addition to specific applications, Crawley's sociability test can be included as an important component of general behavioral screen of mutant mice.

Here we describe a detailed protocol for examination of sociability in mice by using Crawley's sociability and preference for social novelty test. We describe the advantages and possible applications for this procedure, including critical details important for correct interpretation of the results.

Social interactions are a fundamental and adaptive component of the biology of numerous species. Social recognition is critical for the structure and ...

Peering into the Dynamics of Social Interactions: Measuring Play Fighting in Rats

Play fighting in the rat involves attack and defense of the nape of the neck, which if contacted, is gently nuzzled with the snout. Because the movements of one animal are countered by the actions of its partner, play fighting is a complex, dynamic interaction. This dynamic complexity raises methodological problems about what to score for experimental studies. We present a scoring schema that is sensitive to the correlated nature of the actions performed. The frequency of play fighting can be measured by counting the number of playful nape attacks occurring per unit time. However, playful defense, as it can only occur in response to attack, is necessarily a contingent measure that is best measured as a percentage (#attacks defended/total # attacks X 100%). How a particular attack is defended against can involve one of several tactics, and these are contingent on defense having taken place; consequently, the type of defense is also best expressed contingently as a percentage. Two experiments illustrate how these measurements can be used to detect the effect of brain damage on play fighting even when there is no effect on overall playfulness. That is, the schema presented here is designed to detect and evaluate changes in the content of play following an experimental treatment.

Play fighting in the rat involves attack and defense of the nape of the neck, which if contacted, is gently nuzzled with the snout. Because the movements of one animal are countered by the actions of its partner, play fighting is a complex, dynamic interaction. This dynamic complexity raises methodological problems about what to score for experimental studies. We present a scoring schema that is sensitive to the correlated nature of the actions performed. Two experiments illustrate how these measurements can be used to detect the effect of brain damage on play fighting even when there is no effect on overall playfulness. That is, the schema presented here is designed to detect and evaluate changes in the content of play following an experimental treatment.

Play fighting in the rat involves attack and defense of the nape of the neck, which if contacted, is gently nuzzled with the snout. Because the movements ...

Straightforward Assay for Quantification of Social Avoidance in Drosophila melanogaster

Drosophila melanogaster is an emerging model to study different aspects of social interactions. For example, flies avoid areas previously occupied by stressed conspecifics due to an odorant released during stress known as the Drosophila stress odorant (dSO). Through the use of the T-maze apparatus, one can quantify the avoidance of the dSO by responder flies in a very affordable and robust assay. Conditions necessary to obtain a strong performance are presented here. A stressful experience is necessary for the flies to emit dSO, as well as enough emitter flies to cause a robust avoidance response to the presence of dSO. Genetic background, but not their group size, strongly altered the avoidance of the dSO by the responder flies. Canton-S and Elwood display a higher performance in avoiding the dSO than Oregon and Samarkand strains. This behavioral assay will allow identification of mechanisms underlying this social behavior, and the assessment of the influence of genes and environmental conditions on both emission and avoidance of the dSO. Such an assay can be included in batteries of simple diagnostic tests used to identify social deficiencies of mutants or environmental conditions of interest.

Straightforward Assay for Quantification of Social Avoidance in Drosophila melanogaster

Here, we present a protocol to quantify the avoidance of stressed individuals. This paradigm is powerful yet user-friendly and can be used to assess the influence of genes and environment on one kind of social interaction in Drosophila melanogaster.

Drosophila melanogaster is an emerging model to study different aspects of social interactions. For example, flies avoid areas previously occupied by ...

Conditions Affecting Social Space in Drosophila melanogaster

The social space assay described here can be used to quantify social interactions of Drosophila melanogaster &#8212; or other small insects &#8212; in a straightforward manner. As we previously demonstrated 1, in a two-dimensional chamber, we first force the flies to form a tight group, subsequently allowing them to take their preferred distance from each other. After the flies have settled, we measure the distance to the closest neighbor (or social space), processing a static picture with free online software (ImageJ). The analysis of the distance to the closest neighbor allows researchers to determine the effects of genetic and environmental factors on social interaction, while controlling for potential confounding factors. Diverse factors such as climbing ability, time of day, sex, and number of flies, can modify social spacing of flies. We thus propose a series of experimental controls to mitigate these confounding effects. This assay can be used for at least two purposes. First, researchers can determine how their favorite environmental shift (such as isolation, temperature, stress or toxins) will impact social spacing 1,2. Second, researchers can dissect the genetic and neural underpinnings of this basic form of social behavior 1,3. Specifically, we used it as a diagnostic tool to study the role of orthologous genes thought to be involved in social behavior in other organisms, such as candidate genes for autism in humans 4.

Conditions Affecting Social Space in Drosophila melanogaster

The effect of genes and environment on social space of Drosophila melanogaster can be quantified through a powerful but straightforward analytical paradigm. We show here different factors that can affect this social space, and thus need to be taken into consideration when designing experiments in this paradigm.

The social space assay described here can be used to quantify social interactions of Drosophila melanogaster &#8212; or other small insects &#8212; in a ...

How to Obtain Reliable Visual Event-related Potentials in Newborns

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable measurements in newborns. Obtaining high-quality, reliable VEPs is crucial for the early detection of abnormal development of the central nervous system in at-risk newborns, and for implementing successful early interventions. Recommendations are based on a previous study which showed that when post-conceptional age, polysomnography-identified sleep stages, and light-emitting diodes (LEDs) googles as the luminous source are controlled, no more than 4 repetitions of VEP averages are required to obtain replicable recordings, variability decreases, and reliable VEPs can be obtained. By controlling for these sources of variability and using statistical analyses, we were able to clearly and reliably identify the amplitude and latency of three main components (NII, PII and NIII) present in 100% of newborns (n = 20) during active sleep. Recording VEPs during awake states, quiet sleep and transitional sleep is not recommended because VEP morphology may differ significantly from one average to the next, leading to the risk of misleading clinical prognoses. Moreover, it is easier to obtain VEPs during active sleep because this state can be clearly and reliably identified at this stage of development, sleep cycles are short enough to allow measurements to be taken in a reasonable time, and the method does not require new o expensive equipment.

Several important points for obtaining high-quality reliable visual evoked potentials (VEPs) in newborns while minimizing variability and the risk of misleading prognoses are presented.

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable ...

Post-Movie Subliminal Measurement (PMSM), for Investigating Implicit Social Bias

New knowledge is continuously gained from a social environment that can influence how people respond to each other. Such responses often occur implicitly, at a subliminal perceptual level, and related brain mechanisms can be experimentally isolated by presenting the stimuli quickly. Subliminal presentation of faces that belong to different ethnicity groups, races, or gender has been shown to be successful in investigating social implicit responses. However, many implicit responses are based on knowledge previously gained about the faces (e.g., sexual orientation, political views, and socioeconomic status) and not solely on physical appearance. Here, a novel method called post-movie subliminal measurement (PMSM) is presented. When watching a socially engaging movie, a spectator gains knowledge about the protagonist and becomes familiar with his/her identity and world views. When the face of the protagonist is presented subliminally after the movie, it evokes an implicit neural response depending on what is learned about the protagonist. With a vast number of movies available, each depicting a variety of people with different identities, the PMSM method enables investigation of the brain&#39;s complex implicit biases in a manner that resembles real-life social perceptions.

Post-Movie Subliminal Measurement PMSM, for Investigating Implicit Social Bias

This protocol describes the use of movies to investigate brain mechanisms underlying implicit social biases during functional magnetic resonance imaging. When the face of a protagonist is presented after a movie subliminally, it evokes an implicit response based on knowledge of the protagonist gained during the movie.

New knowledge is continuously gained from a social environment that can influence how people respond to each other. Such responses often occur implicitly, ...