Mia Thomaidou

114 advertisements, and the online recruitment website Sona (Sona Systems, Tallinn, Estonia). Study participation involved a 2-hour testing appointment at a research laboratory of the Faculty of Social and Behavioral Sciences of Leiden University, the Netherlands. All participants provided written informed consent prior to the start of the experiment. After completing the experiment, all participants were reimbursed by either cash or study credits for their participation. This study was approved by the Leiden University Psychology Research Ethics Committee (CEP18-0816/318) and pre-registered on ClinicalTrials.gov (NCT03793790). Design This study utilized a randomized, two-by-two design, with an additional control group (Figure 1). A randomization list was created by an independent researcher and participants were randomly allocated to one of 5 groups only after the calibration procedure was complete, so to reduce any risk of bias. All participants underwent a two-phase study design of which each phase consisted of two parts. The induction phase (phase 1) comprised an induction part in which associations were learned and an evocation part in which learned associations were tested. The attenuation phase (phase 2) comprised either counterconditioning or extinction to examine the attenuation of the learned responses and a second evocation part to test whether learned associations were still present. Group 1 received conditioning with partial reinforcement and counterconditioning. Group 2 received conditioning with partial reinforcement and extinction. Group 3 received conditioning with continuous reinforcement and counterconditioning. Group 4 received conditioning with continuous reinforcement and extinction. Group 5 (the sham control group) received sham conditioning and also

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