The first and last picture of the false-belief task.
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Pictures of the false-belief task show the set-up of the containers before the protagonist left the room (a) and after his return (b).To assess salivary cortisol concentrations, three saliva samples were collected throughout the experiment. Salivettes (Sarstedt, Nümbrecht, Germany) were used to take samples before (baseline), as well as 20 and 35 minutes after the onset of the treatment. Samples were stored at -20°C until biochemical analysis. The fraction of free cortisol was assessed using an immunoassay (IBL, Hamburg). Mean intra- and inter-assay coefficients of variance were below 9%.Statistical analyses were conducted using IBM SPSS Statistics (Version 29.0) and JASP (Version 0.16.4). T-tests for independent samples were used to compare the mean subjective stress ratings of both conditions. A repeated-measures ANOVA was conducted to check if there were differences in salivary cortisol concentrations between both conditions throughout the experiment. To test the main hypotheses, t-tests for independent samples were used to check if there were differences in the participants’ mean probability ratings for each of the containers.