Cx 300 2

Stimuli and feedback presentation and response recording were performed with an Arduino Mega 2560 and two forcesensitive resistors (FSR) separated 0.5 cm from each other, connected to PC #1 (the EEG data were recorded by PC #2, see below; see Figure 1a). We used custom-written C code and adapted code from a program originally designed for Arduino Uno (Schultz & van Vugt, 2016) in order to present sounds with sinusoidal waveform. According to Schultz, the combination Arduino-FSR has the shortest latency between the time of contact and the time of occurrence of the feedback (0.6 ms) and also the smallest latency variability (0.3 ms), among other features. Non-EEG subjects used Sennheiser HD 280 Pro headphones; EEG subjects used Sennheiser CX 300-II ear-canal phones. To avoid visual feedback from their own finger movement, the subjects were asked to fix gaze at a cross in the screen and a vertical cardboard screen was put to block peripheral vision. Subjects set sound volume to a comfortable level. The code for controlling the experiment and the code for data analysis were written in MATLAB ® .

A 680 Hz tone with 50 ms duration (Knolle et al., 2013b ) was generated using Praat software (Boersma and Weenink, 2013) . Tones were presented at ca. 70 dB sound pressure level via headphones (Sennheiser CX 300-II).