Altruistic decisions are influenced by the allocation of monetary incentives in a pain-sharing game.

BACKGROUND: Altruistic behavior is essential to the sustainability of society, but our current understanding of its underlying motivation is limited. In addition to the intrinsic motives to help others, based on empathy, extrinsic motives such as monetary incentives and social reputation influence prosociality. The purpose of this study was to examine the underlying motivations of prosocial behavior under constant or increasing extrinsic motivation settings. METHODS: An experimental task, Altruistic Pain Sharing, was developed in which the participants were asked to share the other participants' pain. In the session with monetary incentives, the incentives were given either constantly (CONSTANT condition) or proportionally (INCREASING condition), to the amount of shared pain. In addition, monetary incentives were not provided in the NO session. The participants experienced different amounts of mechanical pain at the beginning of the task and chose the number of pain stimulations to share, based on their experiences. RESULTS: Compared to the NO session, the INCREASING session exhibited a rise in the mean of shared pain, but not the CONSTANT session. Furthermore, there was a distinct tendency to receive less pain than the other participant in the CONSTANT session, and a tendency to receive more pain than the other participant in the INCREASING session. CONCLUSION: Prosocial behavior was influenced by the presence, as well as the form, of the extrinsic monetary incentives. Our study shows that rewards incentivize individuals to demonstrate a higher level of prosocial behavior, implying that prosocial behavior is itself a mixture of intrinsic and extrinsic motivations, and that an effectively designed rewards system may function to enhance prosocial behavior.

Expectations of the Physiological Responses Can Change the Somatosensory Experience for Acupuncture Stimulation.

Objective: Humans interpret sensory inputs based on actual stimuli and expectations of the stimuli. We investigated whether manipulating information related to the physiological response could change the somatosensory experience of acupuncture. Methods: Twenty-four participants received tactile stimulations with a von Frey filament on the left arm. Participants were informed that they would receive acupuncture stimulations at different angles while they were presented with changes in their peripheral blood flow (PBF) measured with Laser Doppler perfusion imaging. However, in reality, they were observing premade pseudo-biosignal images (six sessions: one circular, two rectangular elongated, two diagonally elongated, and one cross-fixation [control] shape). After each session, the participants reported the intensity and location of the de qi sensations perceived on their arm using a bodily sensation mapping tool. The spatial patterns of the somatic sensations were visualized using statistical parametric mapping. The F1 score was calculated to measure the similarity between the presented pseudo-biosignals and reported de qi response images. Results: The spatial configurations of the presented pseudo-biosignal images and de qi response images were similar. The rectangular elongated pseudo-biosignal shape had a significantly higher F1 score compared to the control. All tactile stimulations produced similar levels of enhanced PBF regardless of the pseudo-biosignal shape. Conclusion: The spatial configurations of somatic sensations changed according to the presented pseudo-biosignal shape, suggesting that expectations of the physiological response to acupuncture stimulation can influence the perceived somatic sensation.

Physiological impact of nanoporous acupuncture needles: Laser Doppler perfusion imaging in healthy volunteers.

BACKGROUND: Recently, porous acupuncture (PA), which is anodized to increase its surface area for higher stimulation intensity, was developed and showed significantly improved therapeutic effects with more comfort as compared with original acupuncture (OA) in vivo. However, the impact of PA on the change of local blood flow as well as its efficacy and acceptability has not yet been confirmed in a clinical trial. In a randomized, controlled crossover clinical trial, we investigated the effects of PA on the change in local blood flow using laser Doppler perfusion imaging and considered the sensation of pain intensity and discomfort severity using a visual analogue scale (VAS) to explore its physiological impact and the possibility of PA in clinical use. METHODS: Twenty-one healthy participants were randomly treated with PA or OA on one side of Zusanli (ST36) and each participant served as his or her own control. Baseline local blood flow and galvanic skin response (GSR) were obtained for 5 min and acupuncture interventions were subsequently performed. Next, local blood flow and GSR were subsequently obtained for 10 min after insertion, 10 min after manipulation, and 5 min after the withdrawal of acupuncture. At the end of the experiment, participants were asked to indicate the sensation of pain intensity at each session of insertion, retention, manipulation, and withdrawal as well as the overall pain intensity and discomfort severity. RESULTS: PA significantly increased the local blood flow as compared with OA and there was no significant difference in GSR between patients treated with PA versus OA in each phase of insertion and manipulation. No significant difference in pain intensity or discomfort severity was found during manipulation, retention, or withdrawal of acupuncture. CONCLUSIONS: These results indicate that PA increases local blood flow, which can be closely related to the observed enhanced performance, without any associated discomfort or pain, suggesting its applicability in clinical practice.