Social interactions are reduced in BTBR mice tested in the semi-natural Visible Burrow System. All comparisons between BTBR and B6 mice are significant, p < 0.05. Approach front (AF), approach back (AB), flight (FL), follow and chase (FO), self groom (SG), and allogroom (AG) are presented as mean frequency ± SEM. Alone (AL) and huddle (HU) are presented as percentage of total time ± SEM. Modified from [32].