Comparison (Chi-square and Binomial tests) between the amount of scraping (SCRA) behaviors in MARK and SHAM conditions: The frequency of SCRA behavior towards both left and right cheeks is reported in the two conditions (SHAM and MARK 1, 2).

There was a significant increase of SCRA towards both sides of the face under MARK 1 condition compared to SHAM condition in three out of four horses. One out of four horses performed SCRA behavior at higher frequency in MARK 2 compared to SHAM condition. The table also shows the SCRA activity performed only towards the left cheek which corresponded to the mark side (MARK 1, left), with the same three horses showing a significant increase of SCRA in MARK 1 compared to the SHAM condition (left). Regarding the SCRA events towards the right cheek (MARK 2, right), there was no difference in SCRA directed to the right cheek between MARK 2 (right) and SHAM condition (right).