Tactile discrimination
We assessed whether participants could discriminate between the different stimulus intensities. In each trial, vibrotactile stimuli of two different stimulus intensities were presented to the right fingertip for 80 ms each, separated by a 1 s pause. Participants then had to indicate whether they perceived the first or second vibration to be stronger by pressing either ‘1’ or ‘2’ on a keyboard, and how confident they were in this choice by providing a certainty score on a scale ranging from 0 (not at all sure) to 100 (completely sure), by providing a mouse click. There were five trials per unique stimulus pair and order, resulting in a total of 30 randomly presented trials.