Examining the reliability and validity of two versions of the Effort-Expenditure for Rewards Task (EEfRT).

The Effort-Expenditure for Rewards Task (EEfRT) has gained validity evidence from several studies. However, various modifications have been applied to the original version, which have never been compared systematically. In Study 1, we tested 120 healthy participants to directly compare two versions of the EEfRT. In Study 2, we tested a larger sample of 394 healthy participants to further examine the original EEfRT. We replicated the split-half reliability of both task versions. However, self-reported personality traits (e.g., trait BAS) correlated with only some task performance parameters in Study 1, which did not replicate for the original EEfRT in Study 2. Our results indicate complex and sometimes inconsistent relations between different personality traits, task properties, and reward attributes.

A low dosage of the dopamine D2-receptor antagonist sulpiride affects effort allocation for reward regardless of trait extraversion.

Dopamine (DA) is known to be involved in various aspects of reward processing and goal-directed behavior. The present preregistered study aims at directly accessing the causal influence of DA activity on reward motivation in humans, while also accounting for trait extraversion. Therefore, we examined the effect of a single dose of the DA D2 receptor antagonist sulpiride (200 mg) on effort allocation in a modified version of the Effort-Expenditure for Reward Task (EEfRT). Based on its presumably DA increasing action, we expected the low dose of sulpiride to increase participants' willingness to allocate effort during the modified EEfRT relative to placebo, especially in trials with low probability of reward attainment. Further, we expected a moderating effect of trait extraversion on the effects of sulpiride. Two hundred and three healthy male participants were tested in a randomized, double-blind between-subjects design. Contrary to our expectations, sulpiride reduced the average number of clicks within the modified EEfRT and did not interact with reward attributes, suggesting a more global and not reward-specific effect of sulpiride. Furthermore, trait extraversion did not moderate the effect of sulpiride. Our results provide initial support for the validity of the modified version of the EEfRT, suggesting a possible inhibiting effect of a low dose of sulpiride on approach motivation regardless of trait extraversion. However, given the mixed pattern of findings and the possible confounding role of motoric abilities, further studies examining these effects are clearly warranted.

Left frontal anodal tDCS increases approach motivation depending on reward attributes.

BACKGROUND: A growing body of literature indicates a correlation between asymmetrical activity of frontal brain sites and approach vs. withdrawal motivation. Yet the causal status of this relationship is presently unclear. Here we examined the effect of anodal tDCS applied over the left dorsolateral prefrontal cortex (dlPFC) on approach motivation, operationalized as effort allocation during the Effort-Expenditure for Reward Task (EEfRT). HYPOTHESIS: We expected left frontal anodal transcranial direct current simulation (tDCS) to increase participants' willingness to allocate more effort during the EEfRT. Based on previous research, we expected this effect to be strongest on trials with low probability of reward attainment. METHODS: 60 right-handed neurologically and psychologically healthy participants (63% female) aged 18-35 were tested in a counterbalanced within-subject design. Participants were invited to our lab twice to complete two 15-min blocks of the EEfRT on each study day, randomly assigned to either an anodal tDCS or a SHAM condition. RESULTS: No main effect of stimulation condition was found, however the interactions of stimulation condition and both probability of reward attainment and reward magnitude reached significance. These interactions indicated that left frontal anodal tDCS specifically increased the percentage of hard task choices (HTC) in trials with low probability of reward attainment and in trials with high reward magnitude. DISCUSSION: The observation of an increasing effect of left frontal anodal tDCS on effort expenditure for reward as indicated by HTC supports the idea of a causal relationship between asymmetric activity of frontal brain sites and approach motivation and hints at moderating effects of task-features on the effects of tDCS.

Mental rotation does not account for sex differences in left-right confusion.

Several studies have demonstrated that women believe they are more prone to left-right confusion (LRC) than men. However, while some studies report that there is also a sex difference in LRC tasks favouring men, others report that men and women perform equally well. Recently, it was suggested that sex differences only emerge in LRC tasks when they involve mental rotation. That is, sex differences that are reported for some LRC tasks are strongly affected by the well-documented male advantage in mental rotation. To test this assumption, 91 participants were investigated on two LRC tasks: The Left-Right Commands Task and the Bergen Left-Right Discrimination Test. Additionally, participants were asked to complete an LRC self-rating questionnaire. To rule out the possibility that sex differences in LRC are confounded by sex differences in mental rotation, male and female participants were matched for mental rotation performance, resulting in a sample of 46 matched participants. These matched participants showed robust sex differences in favour of men in all LRC measurements. This suggests that pronounced sex differences in LRC are a genuine phenomenon that exists independently of sex differences in mental rotation.