The electrode and synchronized walking study: Participants performed 3 tasks outside: eyes open/eyes close, standing, walking alone & walking with experimenter oddball task, and 3 walking with experimenter tasks Only part of the second task (standing and walking oddball) was used for the first paper. Each of 18 participants performed the task using both active (session 1) and passive (session 2) electrodes, in counterbalanced order Task 1: Eyes open / Eyes closed; 1. Participant stands facing a wall with eyes open (or closed) for 1 min. Then 1 min of eyes closed (or open). This is counterbalanced and repeated. 2X each type. Task 2: Oddball task: Standing / Walking alone / Walking together. Participants performed an oddball task in which they listened to the tones through headphones and silently counted the deviant tones. The tones were 800 and 1000 Hz, with the standard/target status counterbalanced across participants. During the walking conditions, participants walked clockwise around an outdoor (roofed) basketball arena, following pylons. Each block was about 5-6 minutes. Blocks were counterbalanced and repeated 2X each. Task 3: Walking together: Natural / Control / Synchronize 3. Participants walked with the experimenter for 6 minutes in 3 conditions. The experimenter listened to a metronome while walking, and synchronized their steps with it (also true during walking together oddball task). During Natural walking, participant is just asked to walk with the experimenter, with no other instruction. In Control, participant is blinded using side-blinders which block their view of the experimenter. In Synchronize, participants try to synchronize their steps with the experimenter. All walking & oddball conditions started with a countdown (this has a specific trigger for oddball conds, not for task 3 conds. It plays during the first ~ 12 seconds of the 6 min trial

• Joanna Scanlon (Feb 2022)