# Read the article [here][4]. # # Read the preprint [here][1]. # After discovering that we had used a wrong version of the impulsivity questionnaire (BIS11A instead of BIS-11), we replaced an earlier version of our preprint with a new version: all BIS-11 related results were false positives (based on scores from one questionnaires scored using a scoring sheet belonging to another questionnaire, which were thus random datapoints) and have been removed from the manuscript. # Abstract # The cognitive enhancing effects of methylphenidate are well established, but the mechanisms remain unclear. We recently demonstrated that methylphenidate boosts cognitive motivation by enhancing the weight on the benefits of a cognitive task in a manner that depended on striatal dopamine. Here we considered the complementary hypothesis that methylphenidate might also act by changing the weight on the opportunity cost of a cognitive task, that is, the cost of foregoing alternative opportunity. To this end, fifty healthy participants (25 women) completed a novel cognitive effort discounting task that required choices between task and leisure. They were tested on methylphenidate, placebo as well as the selective D2-receptor agent sulpiride, the latter to strengthen inference about dopamine receptor selectivity of methylphenidate’s effects. Furthermore, they also underwent an [18F]DOPA PET scan to quantify striatal dopamine synthesis capacity. Methylphenidate boosted choices of cognitive effort over leisure across the group, and this effect was greatest in participants with more striatal dopamine synthesis capacity. The effects of sulpiride did not reach significance. This study strengthens the motivational account of methylphenidate’s effects on cognition and suggests that methylphenidate reduces the cost of mental labor by increasing striatal dopamine. # Data availability # The data and scripts used in this article will be made publicly available after manuscript acceptance at the following web address: https://doi.org/10.34973/vz46-0h59. Prior to accessing and downloading the shared data, users must create an account. It is possible to use an institutional account or a social ID from Google, Facebook, Twitter, LinkedIn or Microsoft. After authentication, users must accept the Data Use Agreement (DUA), after which they are automatically authorized to download the shared data. The DUA specifies whether there are any restrictions on how the data may be used. The Radboud University and the Donders Institute for Brain, Cognition and Behaviour will keep these shared data available for at least 10 years. For now, analysis code is available on [GitHub][2]. # NeuroVault # Unthresholded statistical maps of the voxel-wise Ki analyses are available on [NeuroVault][3]. # File Directory # - Pre-Registration - Project proposal Donders Institute (short slideshow that summarizes project) [1]: https://www.biorxiv.org/content/10.1101/859637v3 [2]: https://github.com/LiekeHofmans/MPH_DA_colorwheel [3]: https://neurovault.org/collections/8306/ [4]: https://doi.org/10.1038/s41386-020-00834-1