Catecholaminergic modulation of trust decisions

Abstract

Rationale: Trust is a key component of social interactions. In order to assess the trustworthiness of others, people rely on both information learned from previous encounters, as well as on implicit biases associated with specific facial features.

Objective: Here, we investigated the role of catecholamine (dopamine and noradrenaline) transmission on trust decisions as a function of both experienced behavior and facial features.

Methods: To increase catecholamine levels, methylphenidate (MPH, i.e., Ritalin®, 20 mg) was administered to participants (N = 24) prior to their playing a well-studied economic task, namely the Trust Game (Berg et al. 1995). We measured the amount of money invested with a variety of game partners. Across game partners, we manipulated two aspects of trust: the facial trust level (high facial trust, low facial trust, and non-social) and the likelihood of reciprocation (high, low).

Results: Results demonstrated no main effect of MPH on investments, but rather a selective lowering of investments under MPH as compared with placebo with the game partners who were low on facial trustworthiness and were low reciprocators.

Conclusion: These results provide evidence that MPH administration impacts social trust decision-making, but does so in a context-specific manner.

Keywords: Catecholamines; Decision-making; Methylphenidate; Ritalin; Social learning; Trust; Trust Game.

Fig. 1

a The Trust Game. There are two players in the game, Investor and Trustee. The Investor is provided with a 10 Euro endowment. From this endowment, the Investor must choose how much money they will send to the Trustee, with this being any amount from 0 to 10 Euros, in increments of 1 Euro. The money transferred is multiplied by a factor of 4 by the experimenter, such that the Trustee receives this quadrupled amount. Finally, the Trustee decides if they want to send any money back to the Investor, with no requirement that any money is returned. b This represents the time course of a single trial within the experiment. Each square represents a screen. A fixation cross was shortly presented, followed by the face and the name of the game partner for that trial (3000 ms). The participant could then decide how much they wanted to invest in the game partner, by pressing a button to increase the investment amount in 1 Euro increments. When the participant was satisfied with their choice, they pressed an additional button to finalize the investment. If no offer was submitted in time (6000 ms), all of the money for the round was forfeited. The final feedback screen informed the participant whether their game partner had shared or kept the money. The length of a trial varied between 13 and 16 s

Fig. 2

The figure illustrates the mean investments (± SE) with the three levels of facial Trust Game partners, in the first trial of the Trust Game only

Fig. 3

The figure presents the three-way interaction of Drug × Reciprocation Probability × Facial Trust. The y-axis shows the difference in investment amounts between MPH and placebo (± SE)