Animal research has established that effects of hormones on social behaviour depend on characteristics of both individual and environment. Insight from research on humans into this interdependence is limited, though. Specifically, hardly any prior testosterone experiments in humans scrutinized the interdependency of testosterone with the social environment. Nonetheless, recent testosterone administration studies in humans repeatedly show that a proxy for individuals’ prenatal testosterone-to-estradiol ratio, second-to-fourth digit-ratio (2D:4D ratio), influences effects of testosterone administration on human social behaviour. Here, we systematically vary the characteristics of the social environment and show that, depending on prenatal sex hormone priming, testosterone administration in women moderates the effect of the social environment on trust. We use the economic trust game and compare one-shot games modelling trust problems in relations between strangers with repeated games modelling trust problems in ongoing relations between partners. As expected, subjects are more trustful in repeated than in one-shot games. In subjects prenatally relatively highly primed by testosterone, however, this effect disappears after testosterone administration. We argue that impairments in cognitive empathy may reduce the repeated game effect on trust after testosterone administration in subjects with relatively high prenatal testosterone exposure and propose a neurobiological explanation for this effect.

Punishments and rewards are effective means for establishing cooperation in social dilemmas. We compare a setting where actors individually decide whom to sanction with a setting where sanctions are only implemented when actors collectively agree that a certain actor should be sanctioned. Collective sanctioning decisions are problematic due to the difficulty of reaching consensus. However, when a decision is made collectively, perverse sanctioning (e.g. punishing high contributors) by individual actors is ruled out. Therefore, collective sanctioning decisions are likely to be in the interest of the whole group. We employ a laboratory experiment where subjects play Public Goods Games with opportunities for punishment or reward that is implemented either by an individual, a majority, or unanimously. For both punishment and reward, contribution levels are higher in the individual than the majority condition, and higher under majority than unanimity. Often, majority agreement or unanimity was not reached on punishments or rewards.

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Punishments and rewards are effective means for establishing cooperation in social dilemmas. We compare a setting where actors individually decide whom to sanction with a setting where sanctions are only implemented when actors collectively agree that a certain actor should be sanctioned. Collective sanctioning decisions are problematic due to the difficulty of reaching consensus. However, when a decision is made collectively, perverse sanctioning (e.g. punishing high contributors) by individual actors is ruled out. Therefore, collective sanctioning decisions are likely to be in the interest of the whole group. We employ a laboratory experiment where subjects play Public Goods Games with opportunities for punishment or reward that is implemented either by an individual, a majority, or unanimously. For both punishment and reward, contribution levels are higher in the individual than the majority condition, and higher under majority than unanimity. Often, majority agreement or unanimity was not reached on punishments or rewards.

Libertarians in the contemporary free will debate find themselves under attack from two angles. They face the challenge of defending the necessity of indeterminism for freedom against the philosophical mainstream position of compatibilism. And second, they are increasingly forced to argue for the very possibility of indeterministic free will, in the face of the so-called luck objection. Many contemporary libertarians try to overcome the second problem by adopting the causal theory of action (CTA). We argue that this move at the same time undermines their ability to answer the first challenge. On the basis of this, we suggest that CTA might be a theory of action that is biased towards compatibilism. We thus argue that the best strategy for the libertarian is to insist that intentional action itself requires indeterminism. Recent agent-causal accounts offer a promising way of developing such an alternative libertarianism, but we argue that they currently suffer from problems similar to the ones we identify for the event-causalist. If we are correct, then this has an important implication for the contemporary free will debate: action theory should (once again) take centre stage.