Dopamine manipulations modulate paranoid social inferences in healthy people
J.M. Barnby, Vaughan Bell, Quinton Deeley, Mitul A. Mehta
bioRxiv (Cold Spring Harbor Laboratory) December 19, 2019 preprint DOI: 10.1101/2019.12.18.874255 via OpenAlex
Summary
Dopamine transmission influences social attributions related to paranoia, but not the salience of paranormal or other beliefs. In a double-blind, placebo-controlled experiment, 27 healthy men received either L-DOPA (150 mg), haloperidol (3 mg), or placebo across three sessions. Haloperidol reduced attributions of harmful intent in a Dictator Game, while L-DOPA reduced such attributions only in fair conditions. Haloperidol unexpectedly increased attributions of self-interest for opponents' decisions. No changes occurred in belief salience for politics, religion, science, morality, or the paranormal. These results suggest dopamine selectively affects social inferences linked to paranoia, independent of mood or skepticism.
Study at a glance
| Characteristics | Randomized controlled trial Placebo-controlled Double-blind Preregistered |
|---|---|
| Sample size | 27 |
| Population | Healthy male participants |
| Keywords | Paranoia Attribution Paranormal Mood Social cognition |
| Citations | 4 |
| Key finding | Haloperidol reduced attributions of harmful intent, while L-DOPA reduced them only in fair conditions, and neither drug altered belief salience. |
Abstract
Abstract Altered dopamine transmission is thought to influence the formation of persecutory delusions. However, despite extensive evidence from clinical studies there is little experimental evidence on how modulating the dopamine system changes social attributions related to paranoia, and the salience of beliefs more generally. 27 healthy male participants received 150mg L-DOPA, 3mg haloperidol, or placebo in a double blind, randomised, placebo-controlled study, over three within-subject sessions. Participants completed a multi-round Dictator Game modified to measure social attributions, and a measure of belief salience spanning themes of politics, religion, science, morality, and the paranormal. We preregistered predictions that altering dopamine function would affect i) attributions of harmful intent and ii) salience of paranormal beliefs. As predicted, haloperidol reduced attributions of harmful intent across all conditions compared to placebo. L-DOPA reduced attributions of harmful intent in fair conditions compared to placebo. Unexpectedly, haloperidol increased attributions of self-interest for opponents’ decisions. There was no change in belief salience within any theme. These results could not be explained by scepticism or subjective mood. Our findings demonstrate the selective involvement of dopamine in social inferences related to paranoia in healthy individuals.