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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The authors have nothing to disclose.

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>Experimental generation system for computerized behavior research</td>
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			<td>Liquid Crystal Display Monitor</td>
			<td>ROYAL PHILIPS, Netherlands</td>
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			<td>NeuroScan Synamp2 Amplifier</td>
			<td>Neurosoft Labs, Inc, USA</td>
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			<td>bandpass filter 0.05-100 Hz, sampling rate 1000 Hz</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.
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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

JoVE Journal

Neuroscience

520 Görüntüleme.  Harbin Engineering University. Bu protokol, araştırmacıların her katılımcı için dinamik olarak bir kayıtsızlık noktası oluşturmasını sağlayarak, herhangi bir önyargılı kayıtsızlık noktasının zamanlararası seçimlerin değerlendirilmesi üzerindeki etkisini etkili bir şekilde ortadan kaldırır. Olayla ilgili potansiyel veya ERP teknikleri, yüksek zamansal çözünürlük, farklı bilişsel süreçlerin zamansal dizisinin farklılaşmasını sağlar. Ek olarak, ERP bileşenleri belirli bilişsel s...