Presentation software package

Infants were seated on their parents’ lap and sat approximately 60 cm from the screen (23-inch monitor). The infants wore an fNIRS fabric cap (EasyCap, Germany) which was secured in place using infant overalls and outside netting. Stimuli were presented using the Presentation software package (Neurobehavioral Systems, United States). The video stimulus was played for a total of 7 mins while fNIRS data were being recorded. Parents were asked to remain quiet throughout the fNIRS recording session. Sessions were video-recorded to allow offline coding of infants’ behavior and cap placement.

Before fMRI scanning, participants were provided with experimental instructions and auditory stimuli to familiarize themselves with the experimental settings, and the researchers ensured that the participants fully understood the MI tasks to be performed during the experiment. Since no participant responses were required during the scanning, the researchers checked whether the participants were awake and whether they had made any experimental errors (e.g., missing the specific condition in a session) at the inter-session interval. The experimental paradigm was presented with the Presentation software package (Neurobehavioral Systems, Davis, CA, http://www.neurobs.com). The participants were instructed to ME and MI for grasping and releasing the target with the right hand in the same manner with training during the fMRI experiment. The target object was only used during training sessions and removed during the fMRI experiment so as not to evoke tactile sensations which can substantially influence brain activity during ME.

We used grayscale images of faces (Karolinska Directed Emotional Faces)61 , houses (Stanford Vision Lab stimulus set)62 and human bodies (Bodily Expressive Action Stimulus Test set)63 (link). All images were cropped to 200 × 200 pixel dimensions and normalized using the SHINE toolbox for MATLAB64 (link) (v2014a, The MathWorks) by adjusting the mean luminance and s.d. of the intensity values for each pixel. Stimuli were presented to participants using the Presentation software package (v16.4, Neurobehavioral Systems).

Participants were asked to do a learning-based decision-making gambling task built upon one we had employed previously (San Martín et al., 2013 (link); San Martín et al., 2016 (link)). Stimuli were presented on a 24 inch LCD monitor using the Presentation software package (Neurobehavioral Systems, Inc., Albany, CA). Participants were seated in a comfortable chair with eyes about ~60 cm from the screen.

The participants listened to 12 pieces of music via headphones while lying down in the MRI scanner. One piece of music was presented per session (Fig. 2), resulting in 12 sessions in total. In each session, a piece of music was presented after a rest period of 30 s. The duration of sessions depended on music pieces, then the mean duration of sessions was 303 s. The order in which the clear and noisy music sessions were presented was randomized. The noisy music sessions were interleaved with clear music sessions. To clarify the duration of their experience of chills in real time, participants reported whether they had chill experience (i.e., chills) or nonchill experience (neutral) in response to the music, using two buttons marked “chills” or “neutral” on an input device (HHSC-1 × 4-D, Current Designs, Inc., Philadelphia, PA, USA) held in their left hand. They were asked to press and hold the appropriate button while listening to the music. At the end of a musical piece, participants were asked to rate how the music made them feel on a 5-point scale (arousal: 1 = low arousal to 5 = high arousal; valence: 1 = unpleasant to 5 = pleasant). Due to technical problems, ratings were not collected from 6 participants. The experiment was programmed with the Presentation software package (Neurobehavioral Systems, Inc., Albany, CA, USA).