Fig 1. Schematic representation of the 4 phases of this study, in chronological order.

All participants completed identical fMRI sessions before and after 5 consecutive days of behavioural training. Following the final fMRI session, participants returned to the laboratory for a surprise behavioural retest, where they were asked to tie the 13 knots they had physically practiced, the 13 knots they had watched their partner learn to tie, and 13 remaining knots they had never practiced or watched being tied. In the physical practice condition, in order to cater to each individual’s speed of learning, participants were able to start, stop, and restart the training videos as needed in order to recreate the 13 knots from the physical practice group. Participants were instructed to correctly tie each of these knots once per day of training, and to focus on memorizing how to tie each of these knots. When a participant observed his or her partner learning to tie their group of 13 knots, they sat next to their partner and watched their tying attempts. The computer monitor was angled in such a way that the observing partner could not see what the tying partner was watching on screen. The individuals in this photograph have provided written informed consent to publish their image.